Title of Invention	A PROCESS FOR PREPARING A PYRIDAZIN-3-ON DERIVATIVE
Abstract	pyridazin-3-on derivative of the formula (1): in which R<sup>2</sup> is a hydrogen atom or a C<sub>1</sub>-C<sub>3</sub> alkyl group, R<sup>3</sup> is a hydrogen atom or a C<sub>1</sub>-C<sub>3</sub> alkyl group, and Q is an optionally substituted phenyl group can be prepared at a high yield and high purity by ring closing a carboxylic acid derivative of the formula (2): in which R<sup>2</sup>, R<sup>3</sup> and Q are the same as defined above, or its salt in the presence of a nitrogen-containing aromatic compound and a boron compound.

Title of Invention

A PROCESS FOR PREPARING A PYRIDAZIN-3-ON DERIVATIVE

Abstract

pyridazin-3-on derivative of the formula (1): in which R2 is a hydrogen atom or a C1-C3 alkyl group, R3 is a hydrogen atom or a C1-C3 alkyl group, and Q is an optionally substituted phenyl group can be prepared at a high yield and high purity by ring closing a carboxylic acid derivative of the formula (2): in which R2, R3 and Q are the same as defined above, or its salt in the presence of a nitrogen-containing aromatic compound and a boron compound.

Full Text	DESCRIPTION PROCESS FOR PREPARING PYRIDAZIN-3-0N DERIVATIVES FIELD OF THE INVENTION The present invention relates to a process for preparing pyridazin-3-on derivatives. BACKGROUND ART WO97/7104 discloses that pyridazin-3-on derivatives have good herbicidal activities, and W098/17632 discloses that carboxylic acids derivatives and their salts are useful intermediates for the preparation of pyridazin-3-on derivatives, and a process for preparing pyridazin-3-on derivatives from such intermediates. For example, W098/17632 discloses a process of reacting a lower carboxylic acid and a base with such an intermediate. However, the disclosed process does not always produce a desired product at an industrially satisfactory yield and purity. SUMMARY OF THE INVENTION One object of the present invention is to provide a process for preparing pyridazin-3-on derivatives from carboxylic acid derivatives or their salts advantageously in an industrial scale. This and other objects are accomplished by a method for preparing a pyridazin-3-on derivative of the formula (1): Optionally be substituted, Comprising the step of ring closing a carboxylic acid derivative of the formula (2) : wherein RS R1and Q are the same as defined above, or its salt in the presence of a nitrogen-containing aromatic compound and a boron compound, DETAILED DESCRIPTION OF THE INVENTION The carboxylic acid of the formula (2) or its salt, which is a raw material used in the process of the present invention, will be explained. In the carboxylic acid of the formula (2) or its salt, examples of a substituent which may optionally present on the phenyl group Q include halogen atoms, and a group of the formula: -ZR in which Z is an oxygen atom or a sulfur atom, and R1is a hydrogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a cycloalkyl group, a benzyl group, a C1-C6 alkenyl group, a C3-C 6 haloalkenyl group, a C1-C6 alkynyl group, a C3-C6 haloalkynyl group, a cyano-C1-C6 alkyl group, a C2-C8 (alkoxyalkyl) group, a C1-C6 (alkoxy thioalkyl) group, a carboxy-C1-C6 alkyl group, alkoxy) carbonyl-C1-C6 alkyl group, [ {C1-C4 alkoxy) Ci-C4 alkoxy] carbonyl-C1-C6 alkyl group, a (C1-C6 cycloalkoxy) carbonyl-C’-Cg alkyl group or a [ (C1-C6 alkoxy)carbonyl-C1-C6 alkyl]oxycarbonyl-C1-C6 alkyl group, wherein the positions and number of the substituents are arbitrary. Preferably, the group Q is an optionally substituted phenyl group of the formula (3) : wherein X is a hydrogen atom or a halogen atom, Y is a halogen atom, and W is a hydrogen atom or a group of the formula: -ZR’ in which Z and R’ are the same as defined above. Examples of the halogen atom for X and Y include a fluorine atom, a chlorine atom, a bromine atom, etc. Examples of the C1-C6 alkyl group for R’ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert.-butyl group, an amyl group, an isoamyl group, a tert.-amyl group, etc. Examples of the C1-C6 haloalkyl group include a 2-chloroethyl group, a 2-bromoethyl group, a 2, 2,2-trifluoroethyl group, etc. Examples of the C1-C6 cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc. Examples of the C3-C6 alkenyl group include an allyl group, a l-methyl-2-propenyl group, a 3-butenyl group, a 2-butenyl group, a 3-methyl-2-butenyl group, a 2"methyl-3-butenyl group, etc. Examples of the C1-C6 haloalkenyl group include a 2-chlorO"2-propenyl group, a 3,3-dichloro-2-propenyl group, etc. Examples of the C3-C6 alkynyl group include a property group, . a l-methyl-2-propynyl group, a 2-butynyl group, a 1,1- dimethyl-2-propynyl group, etc. Examples of the C3-C6 haloalkynyl group include 3-bromopropargyl group, etc. Examples of the cyano-C1-C6 alkyl group include a cyanomethyl group, etc. Examples of the C1-C6 alkoxyalkyl group include a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, etc. Examples of the C1-C6 alkylthioalkyl group include a methy thiomethyl group, a methy thioethyl group, etc. Examples of the carboxy-C1-C6 alkyl group include a carboxymethyl group, a 1-carboxyethyl group, a 2-carboxyethyl group, etc. Examples of the (C1-C6 alkoxy)carbonyl-C1-C6 alkyl group include a methoxycarbonylmethyl group, an ethoxycarbonylmethyl group, a propoxycarbonylmethyl group, an isopropoxycarbonylmethyl group, a butoxycarbonylmethyl group, an isobutoxycarbonylmethyl group, a tert.-butoxycarbonylmethyl group, an amyloxycarbonylmethyl group, an isoamyloxycarbonylmethyl group, a tert.-amyloxy-carbonylmethyl group, a l-methoxycarbonylethyl group, a 1-ethoxycarbonylethyl group, a 1-propoxycarbonylethyl group, a 1- isopropoxycarbonylethyl group, a 1-butoxycarbonylethyl group, a 1-isobutoxycarbonylethyl group, a l-tert.-butoxycarbonylethyl group, a 1-amyloxycarbonylethyl group, a 1-isoamyloxycarbony-ethyl group, a l-tert.-amyloxycarbonylethyl group, etc. Examples of the [ (C1-C4 alkoxy)-C1-C4 alkoxy]carbonyl-C1-C6 alkyl group include a methoxymethoxycarbonylmethyl group, a methoxyethoxycarbonylmethyl group, a 1-methoxyethoxycarbonylethyl group, etc. Examples of the (C1-C6 cycloalkoxy) carbonyl-C1-C6 alkyl group include a cyclobutyloxycarbonylmethyl group, a cyclopentyloxycarbonylmethyl group, a cyclohexyloxycarbonyl-methyl group,' a 1-cyclobutyloxycarbonylethyl group, a 1-cyclopentyloxycarbonylethyl group, a 1-cyclohexyloxy-carbonylethyl group, etc. Examples of the alkoxy) carbonyl-C1-C6 alkyl] oxy-carbonyl-C1-C6 alkyl group include a (methoxycarbonyl)methoxycarbonylmethyl group, an (ethoxycarbonyl)methoxycarbonylmethyl group, etc. Examples of the C1-C3 alkyl group for R’ and R’ include a methyl group, an ethyl group, a propyl group, etc. The salts of the carboxylic acid derivative of the formula (2) may be the salts of the above exemplified carboxylic acids and organic bases. Examples of such organic bases include nitrogen-containing aromatic compounds (e.g. pyridine, 4-dimethylaminopyridine, 2-picoline, 3-picoline, 4-picoline, 5-ethyl-2-methylpyridine, etc.), dialkylaniline derivatives (e.g. N,N-diethylamlne, N,N-diethyl aniline, etc.), tertiary amines (e.g. triethylamine, diisopropylethylamine, tri-n-propylamino, tri-n-butylamine, etc.), and the like. Hereinafter, the specific carboxylic acid derivatives of the formula (2) as the raw materials are exemplified: However, the raw materials that can be used in the present invention are not limited thereto. Examples of the a boron compound to be used in the process of the present invention are as follows: a borane compound of the formula (4): wherein R% R’ and R’ are the same and different and represent a hydroxyl group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a phenyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C1-C4 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a nitro group, an amino group, a carboxyl group, a C1-C3 amide group, a formyl group, a C1-C3 alkylthio group, a dihydroxylboryl group, or a phenyl group which may optionally be substituted with a dihydroxyboryl group), a naphthyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C1-C4 alkyl group or a C1-C3 haloalkyl group), a thienyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom or a C1-C4 alkyl group), a furyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom or a C1-C4 alkyl group), a benzofuranyl group the benzene group of which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C1-C4 alkyl group or a C’-C3 haloalkyl group), or R** and R’ together form a ring; a polymeric boric acid of the formula (5): wherein R’ andR’ are the same as defined above, or R’ andR’ together form a ring, and n is an integer of at least 1; or a borrowing derivative of the formula (6): wherein R’ is the same as defined above; or mixtures thereof. Examples of the C1-C6 alkoxy group for R% R’ and R’ in the formulae (4), (5) and (6) include a methoxy group, an ethoxy group, an isopropoxy group, a n-butoxy group, a tert.-butyl group, etc. Examples of the C1-C6 alkyl group include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec.-butyl group, a tert.-butyl group, a n-pentyl group, a cyclopentyl group, a n-hexyl group, a cyclohexyl group, etc. Examples of the phenyl group which may optionally be substituted include a phenyl group, a 2-fluorophenyl group, a 3-fluorophenyl group, a 4-fluorophenyl group, a 2-chlorophenyl ; group, a 3-chlorophenyl group, a 4-chlorophenyl group, a 2- bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2, 3-difluorophenyl group, a 3,4-difluorophenyl group, a 2,4-difluorophenyl group, a 2,5-difluorophenyl group, a 2,6-difluorophenyl group, a 3,5-difluorophenyl group, 2,3-dichlorophenyl group, a 3,4-dichlorophenyl group, a 2,4-dichlorophenyl group, a 2,5-dichlorophenyl group, a 2,6-dichlorophenyl group, a 3,5-dichlorophenyl group, a 2,3-dibromophenyl group, a 3,4-dibroinophenyl group, a 2,4-dibromophenyl group, a 2,5-dibromophenyl group, a 2,6-dibromophenyl group, a 3,5-dibroiaophenyl group, a 2-chloro-3-fluorophenyl group, a 3-chloro-2-fluorophenyl group, a 2-chloro-4-fluorophenyl group, a 4-chloro-2-fluorophenyl group, a 2-chloro-5-fluorophenyl group, a 5-chloro-2-fluorophenyl group, a 2-chloro-6-f luorophenyl group, a 3-chloro-4-f luorophenyl group, a 4-chloro-3-f luorophenyl group, a 3-chloro-5-f luorophenyl group, a 2-bromo-3-fluorophenyl group, a 3-bromo-2-fluorophenyl group, a 2-bromo-4-fluorophenyl group, a 4-bromo-2-fluorophenyl group, a 2-bromo-5-fluorophenyl group, a 5-bromo-2-fluorophenyl group, a 2-bromo-6-fluorophenyl group, a 3-bromo-4-fluorophenyl group, a 4-bromo-3-fluorophenyl group, ,a 3-bromo-5-fluorophenyl group, a 2-bromo-3-chlorophenyl group, a 3-bromo-2-chlorophenyl group, a 2-bromo-4-chlorophenyl group, a 4-bromo-2-chlorophenyl group, a 2-bromo-5-chlorophenyl group, a 5-bromo-2-chlorophenyl group, a 2-bromo-6-chlorophenyl group, a 3-bromo-4-chlorophenyl group, a 4-bromo-3-chlorophenyl group, a 3-bromo-5-chlorophenyl group, a 2,3,4-trifluorophenyl group, a 3,4,5-trifluorophenyl group, a 2,3,4-trichlorophenyl group, a 3,4,5-trichlorophenyl group, a 2,3,4-tribromophenyl group, a 3,4,5-tribromophenyl group, a 2-tolyl group, a 3-tolyl group, a 4-tolyl group, a 2-ethylphenyl group, a 3-ethylphenyl group, a 4-ethylphenyl group, a 2,3-xylyl group, a 3,4-xylyl group, a 2,4-xylyl group, a 2,5-xylyl group, a 2,6-xylyl group, a 3,5-xylyl group, a mesityl group, a 2-trifluoromethylphenyl group, a 3-trifluoromethylphenyl group, a 4-trifluoromethylphenyl group, a 3,5-bis(trifluoromethyl)phenyl group, a 2-anisyl group, a 3-anisyl group, a 4-anisyl group, a 2-nitrophenyl group, a 3-nitrophenyl group, a 4-nitrophenyl group, a 2-aminophenyl group, a 3-aininophenyl group, a 4-aminophenyl group, a 2-carboxyphenyl group, a 3-carboxyphenyl group, a 4-carboxyphenyl group, a 2-acetamidophenyl group, a 3-acetamidophenyl group, a 4-acetainidophenyl group, a 2-formylphenyl group, a 3-formylphenyl group, a 4-formylphenyl group, a 2-methylthiophenyl group, a 3-methylthiophenyl group, a 4-methylthiophenyl group, a 2-(dihydroxyboryl)phenyl group, a 3-(dihydroxyboryl)phenyl group, a 4-(dihydroxyboryl)phenyl group, a 2-biphenyl group, a 3-biphenyl group, a 4-biphenyl group, a 4-[4'-(dihydroxyboryl)phenyl]phenyl group, etc. Examples of the naphthyl group which may optionally be substituted include a 1-naphthyl group, 2-naphthyl group, a 3-fluoro-l-naphthyl group, a 4-fluoro-l-naphthyl group, a 5-fluoro-1-naphthyl group, a 6-fluoro-l-naphthyl group, a 3-fluoro-2-naphthyl group, a 4-fluoro-2-naphthyl group, a 5-fluoro-2-naphthyl group, a 6-fluoro-2-naphthyl group, a 3-chloro-1-naphthyl group, a 4-chloro-l-naphthyl group, a 5-chloro-1-naphthyl group, a 6-chloro-l-naphthyl group, a 3-chloro-2-naphthyl group, a 4-chloro-2-naphthyl group, a 5-chloro-2-naphthyl group, a 6-chloro-2-naphthyl group, a 3- brjomo-1-naphthyl group, a 4-bromo-l-naphthyl group, a 5-bromo-1-naphthyl group, a 6-bromo-l-naphthyl group, a 3-bromo-2-naphthyl group, a 4-broiao-2-naphthyl group, a 5-bromo-2-naphthyl group, a 6"bromo-2-naphthyl group, a 3-methyl-1-naphthyl group, a 4-niethyl-l-naphthyl group, a 5-methyl-1-naphthyl group, a 6-methyi-l-naphthyl group, a 3-iaethyl-2-naphthyl group, a 4-methyl-2-naphthyl group, a 5-methyl-2-naphthyl group, a 6-methyl-2-naphthyl group, a 3-trifluoromethyl-1-naphthyl group, a 4-trifluoromethyl-l-naphthyl group, a 5-trifluoromethyl-l-naphthyl group, a 6-trifluoroitiethyl-1-naphthyl group, a, 3-trifluoromethyl-2-naphthyl group, a 4-trifluoromethyl-2-naphthyl group, a 5-trifluoromethyl-2-naphthyl group, a 6-trifluoromethyl-2-naphthyl group, etc. Examples of the thienyl group which may optionally be substituted include a 2-thienyl group, a 3-thienyl group, a 3-fluoro-2-thienyl group, a 4-fluoro-2-thienyl group, a 5-fluoro-2-thienyl group, a 2-fluoro-3-thienyl group, a 4-fluoro-3-thienyl group, a 5-fluoro-3-thienyl group, a 3-chloro-2-thienyl group, a 4-chloro-2-thienyl group, a 5-chloro-2-thienyl group, a 2-chloro-3-thienyl group, a 4-chloro-3-thienyl group, a 5-chloro-3-thienyl group, a 3-bromo-2-thienyl group, a 4-bromo-2-thienyl group, a 5-bromo-2-thienyl group, a 2-bromo-3-thienyl group, a 4-bromo"3-thienyl group, a 5-bromo-3-thienyl group, a 3-methyl-2-thienyl group, a 4-methyl-2-thienyl group, a 5-methyl-2-thienyl group, a 2-methyl-3-thienyl group, a 4-methyl-3-thienyl group, a 5-methyl-3-thienyl group, etc. Examples of the furyl group which may optionally be substituted include a 2-furyl group, a 3-furyl group, a 3-fluoro-2-furyl group, a 4-fluoro-2-furyl group, a 5-fluoro"2-furyl group, a 2"fluoro-3-furyl group, a 4-fluoro-3-furyl group, a 5-fluoro"3-furyl group, a 3-chloro-2-furyl group, a 4-chloro-2-furyl group, a 5-chloro-2"furyl group, a 2-chloro"3-furyl group, a 4-chloro-3-furyl group, a 5-chloro-3-furyl group, a 3-bromo-2-furyl group, a 4-bromo"2-furyl group, a 5-bromo-2-furyl group, a 2-bromo-3-furyl group, a-4-bromo-3-furyl group, a 5-bromo-3-furyl group, a 3-methyl-2-furyl group, a 4-methyl-2-furyl group, a 5-methyl-2"furyl group, a 2-methyl"3-furyl group, a 4-methyl-3"furyl group, a 5-methyl-3-furyl group, etc. Examples of the benzofuranyl group which may optionally be substituted include a 2-ben2ofuranyl group, a 3-benzofuranyl group, a 4-fluoro-2"benzofuranyl group, a 5"fluoro-2-benzofuranyl group, a 6-fluoro-2-benzofuranyl group, a 7-fluoro-2-benzofuranyl group, a 4-fluoro-3-benzofuranyl group, a 5-fluoro-3-benzofuranyl group, a 6-fluoro-3-benzofuranyl group, a 7-fluoro"3-benzofuranyl group, a 4-chloro-2-benzofuranyl group, a 5-chloro~2-benzofuranyl group, a 6-chloro-2-benzofuranyl group, a 7"chloro-2-benzofuranyl group, a 4-chloro-3-benzofuranyl group, a 5-chloro-3-benzofuranyl group, a 6-chloro-3-ben2ofuranyl group, a 7-chloro-3-benzofuranyl group, a 4-bromo-2-benzofuranyl group, a 5-bromo-2-benzofuranyl group, a 6-bromo-2-benzofuranyl group, a 7-bromO"2-ben2ofuranyl group, a 4-bromo-3"benzofuranyl group, a 5-bromo-3-benzofuranyl group,’ a 6-bromo-3-benzofuranyl group, a 7-bromo-3-benzofuranyl group, a 4"methyl"2-benzofuratiyl group, a 5-methyl-2-benzofuranyl group, a 6-methyl-2-ben2ofuranyl group, a 7-methyl-2-ben2ofuranyl group, a 4-inethyl-3-benzofuranyl group, a 5-methyl-3-benzofuranyl group, a 6-methyl-3-benzofuranyl group, a 7-inethyl-3-benzofuranyl group, a 4-trifluoromethyl-2-benzofuranyl group, a 5-trifluoromethyl-2-ben2ofuranyl group, a 6-trifluoromethyl-2-benzofuranyl group, a 7-trifluoromethyl-2-benzofuranyl group, a 4-trifluoroinethyl-3-benzofuranyl group, a 5-trifluoromethyl"3-benzofuranyl group, a 6-trifluoromethyl-3-benzofuranyl group, a 7-trifluoromethyl-3-benzofuranyl group, etc. Examples of the combined group of R’ and R’ which form a ring include a C4-C5 alkylene group which may be substituted with at least one methyl group such as a 1, 4-tetramethylene group, or a 1,5"pentamethylene group, and a C2-C4 alkylenedioxy group which may be substituted with at least one methyl group such as a 1, 2-ethylenedioxy group, a 1,2-(1,1,2,2-tetramethyl)ethylene-dioxo group or a 1,3-tetramethylenedioxy group, and a 1,2-phenylenedioxy group, etc. Examples of the borane compound of the formula (4) include boric acid derivatives (e.g. methylboric acid, ethyl boric acid, isopropylboric acid, n-butylboric acid, n-pentylboric acid, cyclopentylboric acid, n-hexylboric acid, cyclohexylboric acid, phenylboric acid, 2-f luorophenylboric acid, 3-f luorophenylboric acid, 4-fluorophenylboric acid, 2-chlorophenylboric acid, 3-chlorophenylboric acid, 4-chlorophenylboric acid, 2-bromo-phenylboric acid, 3-bromophenylboric acid, 4-bromophenylboric acid, 3,5-difluorophenylboric acid, 2,3-dichlorophenylboric acid, 3,4-dichlorophenylboric acid, 2,4-dichlorophenylboric acid, 3, 5-dichlorophenylbcric acid, 3, 5-dibromophenylboric acid, 3-chloro-4-fluorophenylboric acid, 3,4,5-trifluorophenylboric acid, 3,4,5-trichlorophenylboric acid, 3,4,5-tribromophenyl-boric acid, 2,3,4,5,6-pentafluorophenylboric acid, 2-tolylboric acid, 3"tolylboric acid, 4-tolylboric acid, 4-ethylphenylboric acid, 3,4-xylylboric acid, mesitylboric acid, 2-trifluoromethylphenylboric acid, 3-trifluoromethylphenylboric acid, 4-trifluoromethylphenylboric acid, 3,5-bis(trifluoromethyl)phenylboric acid, 2-anisylboric acid, 3-anisylboric acid, 4-anisylboric acid, 3-nitrophenylboric acid, 4-nitrophenylboric acid, 3-aminophenylboric acid, 2-carboxyphenylboric acid, 4-carboxyphenylboric acid, 3-acetamidophenylboric acid, 2-forinylphenylboric acid, 3-foirmylphenylboric acid, 4-formylphenylboric acid, 2-methylthiophenylboric acid, 4-methylthiophenylboric acid, 4-biphenylboric acid, 1,2-phenylenediboric acid, 1,3-phenylenediboric acid, 1,4-phenylenediboric acid, 4,4'-biphenyleneboric acid, 1-naphthylboric acid, 2-naphthylboric acid, 2-thienylboric acid, 3-thienylboric acid, 5-chloro-2-thienylboric acid, 2-furylboric acid, 3-furylboric acid, 2-benzofuranylboric acid, 3-benzofuranylboric acid, etc,); borinic acid derivatives (e.g. dimethylborinic acid, diethylborinic acid, diphenylborinic acid, bis(3,4,5-trifluorophenyl)borinic acid, bis(2,3,4,5,6- pentafluorophenyl) borinic acid, bis (4-methylphenyl) borinic acid, bis[3,5-bis(trifluoromethyl)-phenyl]borinic acid, etc.); trimethyl borane, triethyl borane, triphenylborane, tris(3,4,5-trifluorophenyl)borane, tris(2,3,4,5,6- pentafluorophenyl)borane, tris(4-methylphenyl)borane, tris[3,5-bis(trifluoromethyl)phenyl]borane, tris (3-nitrophenyl)borane, dimethoxyphenylborane, 2-phenyl-l,3,2-dioxabororane, 2-phenyl-4,4,5, 5-tetramethyl-l,3,2-dioxabororane, dimethoxy-(4-methylphenyl)borane, 2-(4-methyl)phenyl-l,3,2-dioxabororane, 2-(4-methyl)phenyl-4,4, 5,5-tetramethyl-l,3,2-dioxabororane, dimethoxy-(3,4,5-trifluorophenyl)borane, 2-(3,4,5-trifluoro)phenyl-l,3,2-dioxabororane, 2- (3,4,5-trifluoro)phenyl-4,4,5,5-tetramethyl-1,3,2-dioxabororane, dimethoxy-(2, 3, 4, 5, 6-pentafluorophenyl)borane, 2-(2,3,4,5,6-pentafluoro)phenyl-1,3,2-dioxabororane, 2-(2,3,4,5,6-pentafluoro)phenyl-4,4,5,5-tetramethyl-1, 3,2-dioxabororane, dimethoxy-(3,5-bistrifluoro-methyl)phenylborane, 2-(3,5-bistrifluoromethyl)phenyl-l,3,2-dioxabororane, 2-(3,5-bistrifluoromethyl)phenyl-4,4,5,5-tetramethyl-1, 3,2-dioxabororane, dimethoxy-(3-nitrophenyl)-borane, 2-(3-nitro)phenyl-l,3,2-dioxabororane, 2-(3-nitro)phenyl-4,4,5,5-tetramethyl-l,3,2-dioxabororane, etc. In a polymeric boric acid of the formula (5) , n is an integer of 1 or more, and preferably from 1 to 5. Examples of the polymeric boric acid of the formula (5) include boric acid derivatives or borinic acid derivative, and their anhydrides among the above borane compounds of the formula (4) . Examples of the boroxine derivative of the formula (6) include trimethylboroxine, triethyl boroxine, triphenyl boroxine, tris(3,4,5-trifluorophneyl)boroxine, tris(2,3,4,5,6-pentafluorophenyl)boroxine, tris(4- methyl phenyl)boroxine, tris[3,5’ bis(trifluoromethyl)phenyl]boroxine, tris(3- nitro phenyl)boroxine, etc. Preferred examples of the borane compound (4), the polymeric boric acid (5) or the boroxine derivative (6) include methylboric acid, n-butylboric acid, phenylboric acid, 3-fluorophenylboric acid, 4-fluorophenylboric acid, 4-chlorophenylboric acid, 4-bromophenylboric acid, 3,5-dichlorophenylboric acid, 3-chloro-4-fluorophenylboric acid, 4-tolylboric acid, 3-trifluoromethyIphenylboric acid, 4-trifluoromethylphenylboric acid, 3,5- bis(trifluoromethyl)phenylboric acid, 3-anisylboric acid, 3-nitrophenylboric acid, 4-carboxyphenylboric acid, 3-acetamidophenylboric acid, 3-formylphenylboric acid, 4-formylphenylboric acid, 4-methylthiophenylboric acid, 2-naphthylboric acid, 1, 4-phenylenediboric acid, diphenylborinic acid, bis(4-methylphenyl)borinic acid, and their polymeric derivatives (anhydrides); triphenylborane, tris (4-methylphenyl)borane, triphenylboroxine, tris (4-methylphenyl)boroxine, and the like. Particularly preferred compounds are phenylboric acid, 4-tolylboric acid and their anhydrides; triphenylboroxine and tris (4-methyl)phenylboroxine. Among the borane compounds of the formula (4) , borinic acid derivatives in which one of R% R’ and Rg is a hydroxyl group, or boric acid derivatives in which two of R\ R’ and Rg are hydroxyl groups may also form polymeric derivatives (anhydrides) represented by the formula (5) or (6) . In the present invention. monomeric compounds, polymeric compounds and their mixtures can be used. Now, a nitrogen-containing aromatic compound used in the process of the present invention is explained. A nitrogen-containing aromatic compound used in the process of the present invention is’ usually pyridine, quinoline or isoquinoline, which may optionally be substituted with at least one.substituent selected from a halogen atom (e.g. a fluorine atom, a chlorine atom, a bromine atom and an iodine atom) , a alkyl group (e.g. a methyl group, an ethyl group, a propyl group, an isopropyl group, etc.) and a di alkyl) amino group. Specific examples of such a nitrogen-containing aromatic compound include pyridine, quinoline, isoquinoline, 4- dimethylaminopyridine, 2-picoline, 3-picoline, 4-picoline, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 3,4- autodyne, 3,5-lutidine, 3-chloropyridine, 2-ethyl-3-methylpyridine, 5-ethyl-2-methylpyridine, etc. Preferred nitrogen-containing aromatic compounds are pyridines which may be substituted with at least one alkyl group, in particular, at least one C1-C3 alkyl group, for example, 2-picoline, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2, 6-lutidine, 2-ethyl-3-methylpyridine, 5-ethyl-2"methylpyridine, etc. Among them, pyridines having a substituent at the 2-position, for example, 5-ethyl-2-methylpyridine are particularly preferred. The combination of a boron compound and a nitrogen-containing aromatic compound can be the combination of the above exemplified compounds. In particular, the combination of phenylboric acid and 5-ethyl-2-methylpyridine/ the combination of 4-tolylboric acid and S-ethyl-Z-methyl pyridine, the combination of triphenylboroxine and 5-ethyl-2-methylpyridine, and the combination of tris(4-methylphenyl)boroxine and 5-ethyl-2-methylpyridine are preferred from the viewpoint of overall properties. The process of the present invention is usually carried out in a solvent. A reaction temperature is usually in the range between about SO’’C and about 250°C, preferably in the range between about 100’0 and about 200’C. A reaction time is usually from split second to about 48 hours, preferably from 1 to 24 hours. Examples of a solvent which may be used in the process of the present invention include aliphatic hydrocarbons (e.g. heptane, octane, ligroin, etc.), aromatic hydrocarbons (e.g. benzene, toluene, ethylbenzene, xylene, mesityl Ne, etc.), halogeneated hydrocarbons (e.g. 1,2-dichloroethane, chlorobenzene, dichlorobenzene, trichlorobenzene, etc.), ethers {e.g. 1,4-dioxane, ethylene glycol dimethyl ether, methyl tert.-butyl ether, etc.), ketones (e.g. methyl isobutyl ketone, cyclohexanone, etc.), acid amides (e.g. N,N-dimethylformamide, etc.), alcohols (e.g. propanol, butanol, amyl alcohol, ethylene glycol, diethylene glycol, etc.), and their mixtures. The amount of a nitrogen-containing compound is usually from 0.01 to a solvent amount, preferably from 0.1 to 20 moles, per 1 mole of a carboxylic acid derivative of the formula (2) . The amount of a boron compound is usually from 0.0001 to 5 moles, preferably from 0.001 to 3 moles, in terms of a boron exemplified compounds. In particular, the combination of phenylboric acid and 5-ethyl"2-methylpyridine, the combination of 4-tolylboric acid and 5"ethyl-2-methylpyridine, the combination of triphenylboroxine and 5-ethyl-2-methylpyridine, and the combination of tris(4-methylphenyl)boroxine and 5-ethyl-2-methylpyridine are preferred from the viewpoint of overall properties. The process of the present invention is usually carried out in a solvent. A reaction temperature is usually in the range between about 50°C and about 250’0/ preferably in the range between about 100’C and about 200’C. A reaction time is usually from split second to about 48 hours, preferably from 1 to 24 hours. Examples of a solvent which may be used in the process of the present invention include aliphatic hydrocarbons (e.g. heptane, octane, ligroin, etc.), aromatic hydrocarbons (e.g. benzene, toluene, ethylbenzene, xylene, mesityl Ne, etc.), halogeneated hydrocarbons (e.g. 1,2-dichloroethane, chlorobenzene, dichlorobenzene, trichlorobenzene, etc.), ethers (e.g. 1,4-dioxane, ethylene glycol dimethyl ether, methyl tert.-butyl ether, etc.), ketones (e.g. methyl isobutyl ketone, cyclohexanone, etc.), acid amides (e.g. N,N-dimethylformamide, etc.), alcohols (e.g. propanol, butanol, amyl alcohol, ethylene glycol, diethylene glycol, etc.), and their mixtures. The amount of a nitrogen-containing compound is usually from 0.01 to a solvent amount, preferably from 0.1 to 20 moles, per 1 mole of a carboxylic acid derivative of the formula (2) . The amount of a boron compound is usually from 0.0001 to 5 moles, preferably from 0.001 to 3 moles, in tunas of a boron atom, per 1 mole of a carboxylic acid derivative of the formula (2) . The carboxylic acid of the formula (2) is a known compound from W098/17632, or can be prepared by the method described in this WO publication. The carboxylic acid of the formula (2) or its salt has geometric isomers due to the presence of a double bond, optical isomers due to the presence of an asymmetric carbon atom and diastereomers- Any one of such isomers or a mixture thereof may be used in the process of the present invention. In the process of the present invention, the raw material, a solvent and the like can be charged at once, although it is possible to charge a carboxylic acid derivative of the formula (2), a nitrogen-containing compound and the like by several portions to carry out the reaction. After the completion of the reaction, the reaction mixture is post-treated, for example, the reaction mixture as such is concentrated, or it is washed with an aqueous solution of an inorganic acid such as hydrochloric acid, sulfuric acid, etc. and the organic layer is dried and concentrated. If necessary, the concentrated product may be purified by recrystallization or with column chromatography to recover a pyridazin-3-on of the formula (1) . In the process of the present invention, the reaction may be carried out with azeotropic dehydration and/or in the presence of a dehydrator. Examples of such a dehydrator include zeolites such as molecular sieves, silica gel, magnesium sulfate, sodium sulfate, calcium sulfate, copper sulfate, etc. Preferably zeolites such as molecular sieves, in particular, Molecular Sieve 3A, are used. When a solid dehydrator is used, it is removed by filtration from a reaction mixture, and then the reaction mixture is subjected to the above post-treatment to recover a pyrida2in-3-one of the formula (1). Preferred but animating examples of pyridazin-3-on derivatives of the formula (1) are as follows: EFFECTS OF THE INVENTION According to the present invention, pyridazin-3-on derivatives having good herbicidal activities can be obtained at a high yield and high purity. EXAMPLES The present invention will be illustrated by the following examples, which do not limit the scope of the invention in any way. Example 1 3-Carboxy-2-trifluoromethyl-2-hydroxy"l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydra2one) (Compound 2-2) (5.62 g) / phenylboric acid (0.38 g), Molecular Sieve 4A (powder) (2.70 g), toluene (16.14 g) and 5-ethyl-2-methylpyridine (2.82 g) were charged in a reactor, and stirred at a temperature between 110°C and 115°C for 10 hours. After the reaction mixture was cooled to room temperature, methanol (10.0 g) was added to the mixture, and the supernatant was analyzed with LC by an internal standard method, which is explained below. The yield of 2-(2-fluoro-4-chloro"5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on (Compound 1-2) was 91.2%. Internal Standard Method Solutions containing a beforehand isolated objective compound and a standard compound, which is used as the standard of a peak area, in various compositions are prepared, and detected intensities of those solutions are measured by liquid chromatography analysis. Then, a calibration curve is drawn from the weight ratios and the peak area ratios of the objective compound to the standard compound. Thereafter, the precise amount of the standard compound is added to the specific amount of a reaction mixture after the completion of a reaction, and the mixture is analyzed by liquid chromatography. The concentration of the objective compound is calculated using the calibration curve from the obtained peak area ratio of the objective compound to the standard compound. In the examples, ethoxybenzene was used as a standard compound. Examples 2 to 21 The same procedures as those in Example 1 were repeated except that a boric acid derivative shown in Table 1 was used in place of phenylboric acid (0.38 g). Then, the supernatant of the reaction mixture was analyzed by the internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on is shown in Table 1. Example 22 The same procedures as those in Example 11 were repeated except that 0.75 g of 3-nitrophenylboric acid and 3,76 g of 5-ethyl-2-methylpyridine were used. Then, the supernatant of the reaction mixture was analyzed by the internal standard method. The yield of 2-{2-fluoro-4’chloro"5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 91.6%. Example 23 3-Carboxy-2-trifluoromethyl"2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (9.43 g), phenylboric acid (0.31 g) , Molecular Sieve 3A (powder) (8.97 g) , toluene (44.72 g) and 5-ethyl-2-methylpyridine (4,69 g) were charged in a reactor, and stirred at 114""C for 7 hours. After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl"5-trifluoromethylpyrida2in-3-on was 93.5%. Example 24 The same procedures as those in Example 23 were repeated except that 0.61 g of phenylboric acid and 18.83 g of 5-ethyl-2-methylpyridine were used. Then, the filtrate was analyzed with LC by the internal standard method. The yield of 2- (2-f luoro-4"Chloro-5-hydroxyphenyl) -4-methyl-'5-trifluoromethylpyridazin-3-on was 98.2% . Example 25 3-Carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (4.62 g), phenylboric acid (0.55 g) , Molecular Sieve 4A (powder) (8,09 g), toluene (80.69 g) and 5-ethyl-2-methylpyridine (2,83 g) were charged in a reactor, and stirred at a temperature between 109’0 and 112°C for 3 hours. Then, 3-carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-1-(4"Chloro-2-fluoro-5- hydroxyphenylhydrazone) (4.61 g) and 5-ethyl-2"methylpyridine (1.84 g) were charged. After further 3 hours, 3-carboxy-2" trifluoromethyl-2"hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (4.59 g) and 5"ethyl-2-methylpyridine (1.88 g) were charged. After another 3 hours, 3-carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5- hydroxyphenylhydrazone) (4.61 g) and 5-ethyl-2-methylpyridine (1.85 g) were charged, and the mixture was heated at the same temperature as above for 11 hours. After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 88.0%. Example 26 The same procedures as those in Example 25 were repeated except that formed water was isotopically removed. The filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 92.1% . Example 27 The same procedures as those in Example 2 6 were repeated except that monochlorobenzene (80.76 g) was used in place of toluene. The filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 93.7%. Example 28 3-Carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (5.65 g), phenylboric acid (0.73 g), Molecular Sieve 3A (powder) (21,52 g), toluene (107.41 g) and 5-ethyl-2-methylpyridine (3.75 g) were charged in a reactor, and stirred at a temperature between 113 and 115°C for 3 hours. Then, 3-carboxy-2- trifluoromethyl"2-hydroxy-l-butanal-l-{4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (5.63 g) and 5-ethyl-2-methylpyridine (2.51 g) were charged. After further 3 hours, 3-carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (5.63 g) and 5-ethyl-2"methylpyridine (2.50 g) were charged. After another 3 hours, 3-carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (5.66 g) and 5-ethyl-2-methylpyridine (2.49 g) were charged, and the mixture was heated at the same temperature as above for 6 hours. After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on 99.3%. Example 29 The same procedures as those in Example 23 were repeated except that 2, 6-lutidine (8.10 g) was used in place of 5-ethyl-2-methylpyridine (4.69 g) , and the mixture was stirred at a temperature between 115°C and 116°C for 15 hours. The filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 90.9%. Example 30 3-Carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l- (4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (16.68 g), phenylboric acid (0.55 g), Molecular Sieve 3A (powder) (16.24 g) , toluene (80.83 g) and 2-picolin (12.61 g) were charged in a reactor, and stirred at a temperature between 114 and IIS’'C for 7 hours. After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 91.0%. Example 31 3"Carboxy-2-trifluoromethyl-2-hydroxy-l-butanal--l- (4-chloro--2-fluoro-5-hydroxyphenylhydrazone) (16.48 g) , triphenylboroxine (0.48 g) , Molecular Sieve 3A (powder) (16.37 g), toluene (84.91 g) and 5-ethyl-2-methylpyridine (17.06 g) were charged in a reactor, and stirred at a temperature between 114 and 115’C for 6 hours. After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro"4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 93.6%. Example 32 The same procedures as those in Example 31 were repeated except that diphenylborinic acid (0.81 g) was used in place of triphenylboroxine (0.48 g) . After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl) -4-methyl-5-trifluoromethylpyridazin-3-on was 93.4%. Example 33 The same procedures as those in Example 31 were repeated except that triphenylborane (1.14 g) was used in place of triphenylboroxine (0.48 g). After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl) -4-methyl-5--trif luoromethylpyridazin-3-on was 95.4%. Reference Example 1 3-Carboxy-2-trifluoromethyl-2-hydroxy-1-butanal-l-(4-chloro’2-fluoro-5-hydroxyphenylhydrazone) (0.315 g) was dissolved in the mixture of acetic acid (1.0 ml) and pyridine (1.0 ml) under a nitrogen atmosphere, and stirred at 120°C for 8 hours. After the reaction mixture was cooled to room temperature, it was concentrated under reduced pressure, and the residue was diluted with diethyl ether (100 ml) . Then, the diluted solution was washed with 3N hydrochloric acid (each 20 ml) twice, and saturated sodium bicarbonate (30 ml) once, dried over magnesium sulfate, filtrated and concentrated under reduced pressure. The residue was subjected to column chromatography. Thus, 2-(2"fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3--on (0.227 g) was obtained. CLAIMS 1. A method for preparing a pyridazine-S-on derivative of the formula (1): wherein R’ is a hydrogen atom or a C1-C3 alkyl group, R’ is a hydrogen atom or a C1-C3 alkyl group, and Q is a phenyl group which may optionally be substituted, comprising the step of ring closing a carboxylic acid derivative of the fo2:mula (2) : wherein R’, R’ and Q are the same as defined above, or its salt in the presence of a nitrogen-containing aromatic compound and a boron compound• 2. A process according to claim 1, wherein said boron compound is at least one compound selected from: a borane compound of the formula (4): wherein R’ and R’ are the same and different and represent a hydroxyl group, a C1-C6 alkyl group, a alkoxy group, a phenyl group which may optionally be substituted with at least one substituent selected from a halogen atom, a C1-C4 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a nitro group, an amino group, a carboxyl group, a C1-C3 amide group, a formyl group, a C1-C3 alkylthio group, a dihydroxylboryl group and a phenyl group that may optionally be substituted with a dihydroxyboryl group, a naphthyl group which may optionally be substituted with at least one substituent selected from a halogen atom, a C1-C4 alkyl group and a C1-C3 haloalkyl group, a thienyl group which may optionally be substituted with at least one substituent selected from a halogen atom and a C1-C4 alkyl group, a furyl group which may optionally be substituted with at least one substituent selected from a halogen atom and a C1-C4 alkyl group, a benzofuranyl group the benzene group of which may optionally be substituted with at least one substituent selected from a halogen atom, a C1-C4 alkyl group and a Ci"C3 haloalkyl group, or R' and R’ together form a ring; a polymeric boric acid of the formula (5) : wherein R* is the same as defined above- 3. A process according *to claim 1 or 2, wherein the group Q in the formulae (1) and (2) is an optionally substituted phenyl group of the formula (3): wherein X is a hydrogen atom or a halogen atom, Y is a halogen atom, and W is a hydrogen atom or a group of the formula: -ZR’ in which Z is an oxygen atom or a sulfur atom, and R’ is a hydrogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C3-C3 cycloalkyl group, a benzyl group, a alkenyl group, a C3-C6 haloalkenyl group, a C3-C6 alkynyl group, a C3-C6 haloalkynyl group, a cyano-C1-C6 alkyl group, a C1-C6(alkoxyalkyl) group, a C2-C6 (alkoxy thioalkyl) group, a carboxy-C1-C6 alkyl group, (C1-C6 alkoxy) carbonyl-C1-C6 alkyl group, [ alkoxy)-C1-C4 alkoxylcarbonyl-C1-C6 alkyl group, a (C3-C8 cycloalkoxy)carbonyl-C1-C6 alkyl group or a alkoxy)carbonyl-C1-C6 alkyl]oxycarbonyl-C1-C6 alkyl. 4. A process according to claim 3, wherein Z in the formula (3) is an oxygen atom. 5. A process according to claim 3, wherein W in the formula (3) is a hydroxyl group. 6. A process according to any one of claims 3 to 5, wherein X in the formula (3) is a fluorine atom. 7. A process according to any one of claims 3 to 5, wherein X and Y in the formula (3) are a fluorine atom and a chlorine atom, respectively. 8. A process according to any one of claims 1 to 7, wherein R’ and R’ in the formulae (1) and (2) independently represent a hydrogen atom or a methyl group. 9. A process according to anyone of claims 1 to 7, wherein R’ and R’ in the formulae (1) and (2) are a methyl group and a hydrogen atom, respectively. 10. A process according to any one of claims 1 to 9, wherein said nitrogen-containing aromatic compound is pyridine which may optionally be substituted with at least one alkyl group. 11. A process according to any one of claims 1 to 9, wherein said nitrogen-containing aromatic compound is 5-ethyl-2-methylpyridine. 12. A process according to any one of claims 1 to 11, wherein said borane compound of the formula (4) is phenyl boric acid or 4-tolylboric acid. 13. A process according to any one of claims 2 to 11, wherein said boroxine derivative of the formula (6) is triphenyl boroxine or tris(4-methylphenyl)boroxine. 14. A process according to any one of claims 1 to 9, wherein said nitrogen-containing compound is 5-ethyl"2-methylpyridine, and said borane compound of the formula (4) is phenyl boric acid. 15. A process according to any one of claims 1 to 9, wherein said nitrogen-containing compound is 5-ethyl-2-methylpyridine, and said boroxine derivative of the formula (6) is triphenyl boroxine. 16. A process according to any one of claims 1 to 15 wherein ‘ said boron compound is used in an amount of from 0.001 to 3 moles, in terms of a boron atom, per 1 mole of said carboxylic acid / derivative of the formula (2) or its salt. 17. Process according to any one of claims 1 to 16 wherein the reaction is carried out with azeotropic dehydration and/or in the presence of a dehydrator. 18. A process according to claim 17, wherein said dehydrator is a molecular sieve. 19. Aprocess according to claim 18, wherein said molecular sieve is Molecular Sieve 3A. 20. Aprocess according to any one of claims 1 to 19, wherein the reaction is carried out at a temperature of from 100°C to 200°C. A method for preparing a pyridazm-3-on derivative substantially as herein described and exemplified.

Full Text

DESCRIPTION
PROCESS FOR PREPARING PYRIDAZIN-3-0N DERIVATIVES FIELD OF THE INVENTION
The present invention relates to a process for preparing pyridazin-3-on derivatives. BACKGROUND ART
WO97/7104 discloses that pyridazin-3-on derivatives have good herbicidal activities, and W098/17632 discloses that carboxylic acids derivatives and their salts are useful intermediates for the preparation of pyridazin-3-on derivatives, and a process for preparing pyridazin-3-on derivatives from such intermediates. For example, W098/17632 discloses a process of reacting a lower carboxylic acid and a base with such an intermediate.
However, the disclosed process does not always produce a desired product at an industrially satisfactory yield and purity. SUMMARY OF THE INVENTION
One object of the present invention is to provide a process for preparing pyridazin-3-on derivatives from carboxylic acid derivatives or their salts advantageously in an industrial scale.
This and other objects are accomplished by a method for preparing a pyridazin-3-on derivative of the formula (1):

Optionally be substituted,
Comprising the step of ring closing a carboxylic acid derivative
of the formula (2) :

wherein RS R1and Q are the same as defined above, or its salt in the presence of a nitrogen-containing aromatic compound and a boron compound, DETAILED DESCRIPTION OF THE INVENTION
The carboxylic acid of the formula (2) or its salt, which is a raw material used in the process of the present invention, will be explained.
In the carboxylic acid of the formula (2) or its salt, examples of a substituent which may optionally present on the phenyl group Q include halogen atoms, and a group of the formula: -ZR in which Z is an oxygen atom or a sulfur atom, and R1is a hydrogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a cycloalkyl group, a benzyl group, a C1-C6 alkenyl group, a C3-C 6 haloalkenyl group, a C1-C6 alkynyl group, a C3-C6 haloalkynyl group, a cyano-C1-C6 alkyl group, a C2-C8 (alkoxyalkyl) group, a C1-C6 (alkoxy thioalkyl) group, a carboxy-C1-C6 alkyl group, alkoxy) carbonyl-C1-C6 alkyl group, [ {C1-C4 alkoxy) Ci-C4 alkoxy] carbonyl-C1-C6 alkyl group, a (C1-C6 cycloalkoxy) carbonyl-C’-Cg alkyl group or a [ (C1-C6 alkoxy)carbonyl-C1-C6 alkyl]oxycarbonyl-C1-C6 alkyl group, wherein the positions and number of the substituents are

arbitrary.
Preferably, the group Q is an optionally substituted phenyl group of the formula (3) :

wherein X is a hydrogen atom or a halogen atom, Y is a halogen atom, and W is a hydrogen atom or a group of the formula: -ZR’ in which Z and R’ are the same as defined above.
Examples of the halogen atom for X and Y include a fluorine atom, a chlorine atom, a bromine atom, etc.
Examples of the C1-C6 alkyl group for R’ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert.-butyl group, an amyl group, an isoamyl group, a tert.-amyl group, etc.
Examples of the C1-C6 haloalkyl group include a 2-chloroethyl group, a 2-bromoethyl group, a 2, 2,2-trifluoroethyl group, etc.
Examples of the C1-C6 cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc.
Examples of the C3-C6 alkenyl group include an allyl group, a l-methyl-2-propenyl group, a 3-butenyl group, a 2-butenyl group, a 3-methyl-2-butenyl group, a 2"methyl-3-butenyl group, etc.
Examples of the C1-C6 haloalkenyl group include a 2-chlorO"2-propenyl group, a 3,3-dichloro-2-propenyl group, etc.
Examples of the C3-C6 alkynyl group include a property group, . a l-methyl-2-propynyl group, a 2-butynyl group, a 1,1-

dimethyl-2-propynyl group, etc.
Examples of the C3-C6 haloalkynyl group include 3-bromopropargyl group, etc.
Examples of the cyano-C1-C6 alkyl group include a cyanomethyl group, etc.
Examples of the C1-C6 alkoxyalkyl group include a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, etc.
Examples of the C1-C6 alkylthioalkyl group include a methy thiomethyl group, a methy thioethyl group, etc.
Examples of the carboxy-C1-C6 alkyl group include a carboxymethyl group, a 1-carboxyethyl group, a 2-carboxyethyl group, etc.
Examples of the (C1-C6 alkoxy)carbonyl-C1-C6 alkyl group include a methoxycarbonylmethyl group, an ethoxycarbonylmethyl group, a propoxycarbonylmethyl group, an
isopropoxycarbonylmethyl group, a butoxycarbonylmethyl group, an isobutoxycarbonylmethyl group, a tert.-butoxycarbonylmethyl group, an amyloxycarbonylmethyl group, an
isoamyloxycarbonylmethyl group, a tert.-amyloxy-carbonylmethyl group, a l-methoxycarbonylethyl group, a 1-ethoxycarbonylethyl group, a 1-propoxycarbonylethyl group, a 1-
isopropoxycarbonylethyl group, a 1-butoxycarbonylethyl group, a 1-isobutoxycarbonylethyl group, a l-tert.-butoxycarbonylethyl group, a 1-amyloxycarbonylethyl group, a 1-isoamyloxycarbony-ethyl group, a l-tert.-amyloxycarbonylethyl group, etc.
Examples of the [ (C1-C4 alkoxy)-C1-C4 alkoxy]carbonyl-C1-C6 alkyl group include a methoxymethoxycarbonylmethyl group, a

methoxyethoxycarbonylmethyl group, a 1-methoxyethoxycarbonylethyl group, etc.
Examples of the (C1-C6 cycloalkoxy) carbonyl-C1-C6 alkyl group include a cyclobutyloxycarbonylmethyl group, a cyclopentyloxycarbonylmethyl group, a cyclohexyloxycarbonyl-methyl group,' a 1-cyclobutyloxycarbonylethyl group, a 1-cyclopentyloxycarbonylethyl group, a 1-cyclohexyloxy-carbonylethyl group, etc.
Examples of the alkoxy) carbonyl-C1-C6 alkyl] oxy-carbonyl-C1-C6 alkyl group include a (methoxycarbonyl)methoxycarbonylmethyl group, an (ethoxycarbonyl)methoxycarbonylmethyl group, etc.
Examples of the C1-C3 alkyl group for R’ and R’ include a methyl group, an ethyl group, a propyl group, etc.
The salts of the carboxylic acid derivative of the formula (2) may be the salts of the above exemplified carboxylic acids and organic bases. Examples of such organic bases include nitrogen-containing aromatic compounds (e.g. pyridine, 4-dimethylaminopyridine, 2-picoline, 3-picoline, 4-picoline, 5-ethyl-2-methylpyridine, etc.), dialkylaniline derivatives (e.g. N,N-diethylamlne, N,N-diethyl aniline, etc.), tertiary amines (e.g. triethylamine, diisopropylethylamine, tri-n-propylamino, tri-n-butylamine, etc.), and the like.
Hereinafter, the specific carboxylic acid derivatives of the formula (2) as the raw materials are exemplified:

However, the raw materials that can be used in the present invention are not limited thereto.
Examples of the a boron compound to be used in the process of the present invention are as follows:
a borane compound of the formula (4):

wherein R% R’ and R’ are the same and different and represent a hydroxyl group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a phenyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C1-C4 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a nitro group, an amino group, a carboxyl group, a C1-C3 amide group, a formyl group, a C1-C3 alkylthio group, a dihydroxylboryl group, or a phenyl group which may optionally be substituted with a dihydroxyboryl group), a naphthyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C1-C4 alkyl group or a C1-C3 haloalkyl group), a thienyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom or a C1-C4 alkyl group), a furyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom

or a C1-C4 alkyl group), a benzofuranyl group the benzene group of which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C1-C4 alkyl group or a C’-C3 haloalkyl group), or R** and R’ together form a ring; a polymeric boric acid of the formula (5):

wherein R’ andR’ are the same as defined above, or R’ andR’ together form a ring, and n is an integer of at least 1; or a borrowing derivative of the formula (6):

wherein R’ is the same as defined above; or mixtures thereof.
Examples of the C1-C6 alkoxy group for R% R’ and R’ in the formulae (4), (5) and (6) include a methoxy group, an ethoxy group, an isopropoxy group, a n-butoxy group, a tert.-butyl group, etc.
Examples of the C1-C6 alkyl group include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec.-butyl group, a tert.-butyl group, a n-pentyl group, a cyclopentyl group, a n-hexyl group, a cyclohexyl group, etc.
Examples of the phenyl group which may optionally be substituted include a phenyl group, a 2-fluorophenyl group, a 3-fluorophenyl group, a 4-fluorophenyl group, a 2-chlorophenyl ; group, a 3-chlorophenyl group, a 4-chlorophenyl group, a 2-

bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2, 3-difluorophenyl group, a 3,4-difluorophenyl group, a 2,4-difluorophenyl group, a 2,5-difluorophenyl group, a 2,6-difluorophenyl group, a 3,5-difluorophenyl group, 2,3-dichlorophenyl group, a 3,4-dichlorophenyl group, a 2,4-dichlorophenyl group, a 2,5-dichlorophenyl group, a 2,6-dichlorophenyl group, a 3,5-dichlorophenyl group, a 2,3-dibromophenyl group, a 3,4-dibroinophenyl group, a 2,4-dibromophenyl group, a 2,5-dibromophenyl group, a 2,6-dibromophenyl group, a 3,5-dibroiaophenyl group, a 2-chloro-3-fluorophenyl group, a 3-chloro-2-fluorophenyl group, a 2-chloro-4-fluorophenyl group, a 4-chloro-2-fluorophenyl group, a 2-chloro-5-fluorophenyl group, a 5-chloro-2-fluorophenyl group, a 2-chloro-6-f luorophenyl group, a 3-chloro-4-f luorophenyl group, a 4-chloro-3-f luorophenyl group, a 3-chloro-5-f luorophenyl group, a 2-bromo-3-fluorophenyl group, a 3-bromo-2-fluorophenyl group, a 2-bromo-4-fluorophenyl group, a 4-bromo-2-fluorophenyl group, a 2-bromo-5-fluorophenyl group, a 5-bromo-2-fluorophenyl group, a 2-bromo-6-fluorophenyl group, a 3-bromo-4-fluorophenyl group, a 4-bromo-3-fluorophenyl group, ,a 3-bromo-5-fluorophenyl group, a 2-bromo-3-chlorophenyl group, a 3-bromo-2-chlorophenyl group, a 2-bromo-4-chlorophenyl group, a 4-bromo-2-chlorophenyl group, a 2-bromo-5-chlorophenyl group, a 5-bromo-2-chlorophenyl group, a 2-bromo-6-chlorophenyl group, a 3-bromo-4-chlorophenyl group, a 4-bromo-3-chlorophenyl group, a 3-bromo-5-chlorophenyl group, a 2,3,4-trifluorophenyl group, a 3,4,5-trifluorophenyl group, a 2,3,4-trichlorophenyl group, a 3,4,5-trichlorophenyl group, a 2,3,4-tribromophenyl group, a 3,4,5-tribromophenyl group, a

2-tolyl group, a 3-tolyl group, a 4-tolyl group, a 2-ethylphenyl group, a 3-ethylphenyl group, a 4-ethylphenyl group, a 2,3-xylyl group, a 3,4-xylyl group, a 2,4-xylyl group, a 2,5-xylyl group, a 2,6-xylyl group, a 3,5-xylyl group, a mesityl group, a 2-trifluoromethylphenyl group, a 3-trifluoromethylphenyl group, a 4-trifluoromethylphenyl group, a 3,5-bis(trifluoromethyl)phenyl group, a 2-anisyl group, a 3-anisyl group, a 4-anisyl group, a 2-nitrophenyl group, a 3-nitrophenyl group, a 4-nitrophenyl group, a 2-aminophenyl group, a 3-aininophenyl group, a 4-aminophenyl group, a 2-carboxyphenyl group, a 3-carboxyphenyl group, a 4-carboxyphenyl group, a 2-acetamidophenyl group, a 3-acetamidophenyl group, a 4-acetainidophenyl group, a 2-formylphenyl group, a 3-formylphenyl group, a 4-formylphenyl group, a 2-methylthiophenyl group, a 3-methylthiophenyl group, a 4-methylthiophenyl group, a 2-(dihydroxyboryl)phenyl group, a 3-(dihydroxyboryl)phenyl group, a 4-(dihydroxyboryl)phenyl group, a 2-biphenyl group, a 3-biphenyl group, a 4-biphenyl group, a 4-[4'-(dihydroxyboryl)phenyl]phenyl group, etc.
Examples of the naphthyl group which may optionally be substituted include a 1-naphthyl group, 2-naphthyl group, a 3-fluoro-l-naphthyl group, a 4-fluoro-l-naphthyl group, a 5-fluoro-1-naphthyl group, a 6-fluoro-l-naphthyl group, a 3-fluoro-2-naphthyl group, a 4-fluoro-2-naphthyl group, a 5-fluoro-2-naphthyl group, a 6-fluoro-2-naphthyl group, a 3-chloro-1-naphthyl group, a 4-chloro-l-naphthyl group, a 5-chloro-1-naphthyl group, a 6-chloro-l-naphthyl group, a 3-chloro-2-naphthyl group, a 4-chloro-2-naphthyl group, a 5-chloro-2-naphthyl group, a 6-chloro-2-naphthyl group, a 3-

brjomo-1-naphthyl group, a 4-bromo-l-naphthyl group, a 5-bromo-1-naphthyl group, a 6-bromo-l-naphthyl group, a 3-bromo-2-naphthyl group, a 4-broiao-2-naphthyl group, a 5-bromo-2-naphthyl group, a 6"bromo-2-naphthyl group, a 3-methyl-1-naphthyl group, a 4-niethyl-l-naphthyl group, a 5-methyl-1-naphthyl group, a 6-methyi-l-naphthyl group, a 3-iaethyl-2-naphthyl group, a 4-methyl-2-naphthyl group, a 5-methyl-2-naphthyl group, a 6-methyl-2-naphthyl group, a 3-trifluoromethyl-1-naphthyl group, a 4-trifluoromethyl-l-naphthyl group, a 5-trifluoromethyl-l-naphthyl group, a 6-trifluoroitiethyl-1-naphthyl group, a, 3-trifluoromethyl-2-naphthyl group, a 4-trifluoromethyl-2-naphthyl group, a 5-trifluoromethyl-2-naphthyl group, a 6-trifluoromethyl-2-naphthyl group, etc.
Examples of the thienyl group which may optionally be substituted include a 2-thienyl group, a 3-thienyl group, a 3-fluoro-2-thienyl group, a 4-fluoro-2-thienyl group, a 5-fluoro-2-thienyl group, a 2-fluoro-3-thienyl group, a 4-fluoro-3-thienyl group, a 5-fluoro-3-thienyl group, a 3-chloro-2-thienyl group, a 4-chloro-2-thienyl group, a 5-chloro-2-thienyl group, a 2-chloro-3-thienyl group, a 4-chloro-3-thienyl group, a 5-chloro-3-thienyl group, a 3-bromo-2-thienyl group, a 4-bromo-2-thienyl group, a 5-bromo-2-thienyl group, a 2-bromo-3-thienyl group, a 4-bromo"3-thienyl group, a 5-bromo-3-thienyl group, a 3-methyl-2-thienyl group, a 4-methyl-2-thienyl group, a 5-methyl-2-thienyl group, a 2-methyl-3-thienyl group, a 4-methyl-3-thienyl group, a 5-methyl-3-thienyl group, etc.

Examples of the furyl group which may optionally be substituted include a 2-furyl group, a 3-furyl group, a 3-fluoro-2-furyl group, a 4-fluoro-2-furyl group, a 5-fluoro"2-furyl group, a 2"fluoro-3-furyl group, a 4-fluoro-3-furyl group, a 5-fluoro"3-furyl group, a 3-chloro-2-furyl group, a 4-chloro-2-furyl group, a 5-chloro-2"furyl group, a 2-chloro"3-furyl group, a 4-chloro-3-furyl group, a 5-chloro-3-furyl group, a 3-bromo-2-furyl group, a 4-bromo"2-furyl group, a 5-bromo-2-furyl group, a 2-bromo-3-furyl group, a-4-bromo-3-furyl group, a 5-bromo-3-furyl group, a 3-methyl-2-furyl group, a 4-methyl-2-furyl group, a 5-methyl-2"furyl group, a 2-methyl"3-furyl group, a 4-methyl-3"furyl group, a 5-methyl-3-furyl group, etc.
Examples of the benzofuranyl group which may optionally be substituted include a 2-ben2ofuranyl group, a 3-benzofuranyl group, a 4-fluoro-2"benzofuranyl group, a 5"fluoro-2-benzofuranyl group, a 6-fluoro-2-benzofuranyl group, a 7-fluoro-2-benzofuranyl group, a 4-fluoro-3-benzofuranyl group, a 5-fluoro-3-benzofuranyl group, a 6-fluoro-3-benzofuranyl group, a 7-fluoro"3-benzofuranyl group, a 4-chloro-2-benzofuranyl group, a 5-chloro~2-benzofuranyl group, a 6-chloro-2-benzofuranyl group, a 7"chloro-2-benzofuranyl group, a 4-chloro-3-benzofuranyl group, a 5-chloro-3-benzofuranyl group, a 6-chloro-3-ben2ofuranyl group, a 7-chloro-3-benzofuranyl group, a 4-bromo-2-benzofuranyl group, a 5-bromo-2-benzofuranyl group, a 6-bromo-2-benzofuranyl group, a 7-bromO"2-ben2ofuranyl group, a 4-bromo-3"benzofuranyl group, a 5-bromo-3-benzofuranyl group,’ a 6-bromo-3-benzofuranyl group, a 7-bromo-3-benzofuranyl group, a 4"methyl"2-benzofuratiyl group,

a 5-methyl-2-benzofuranyl group, a 6-methyl-2-ben2ofuranyl group, a 7-methyl-2-ben2ofuranyl group, a 4-inethyl-3-benzofuranyl group, a 5-methyl-3-benzofuranyl group, a 6-methyl-3-benzofuranyl group, a 7-inethyl-3-benzofuranyl group, a 4-trifluoromethyl-2-benzofuranyl group, a 5-trifluoromethyl-2-ben2ofuranyl group, a 6-trifluoromethyl-2-benzofuranyl group, a 7-trifluoromethyl-2-benzofuranyl group, a 4-trifluoroinethyl-3-benzofuranyl group, a 5-trifluoromethyl"3-benzofuranyl group, a 6-trifluoromethyl-3-benzofuranyl group, a 7-trifluoromethyl-3-benzofuranyl group, etc.
Examples of the combined group of R’ and R’ which form a ring include a C4-C5 alkylene group which may be substituted with at least one methyl group such as a 1, 4-tetramethylene group, or a 1,5"pentamethylene group, and a C2-C4 alkylenedioxy group which may be substituted with at least one methyl group such as a 1, 2-ethylenedioxy group, a 1,2-(1,1,2,2-tetramethyl)ethylene-dioxo group or a 1,3-tetramethylenedioxy group, and a 1,2-phenylenedioxy group, etc.
Examples of the borane compound of the formula (4) include boric acid derivatives (e.g. methylboric acid, ethyl boric acid, isopropylboric acid, n-butylboric acid, n-pentylboric acid, cyclopentylboric acid, n-hexylboric acid, cyclohexylboric acid, phenylboric acid, 2-f luorophenylboric acid, 3-f luorophenylboric acid, 4-fluorophenylboric acid, 2-chlorophenylboric acid, 3-chlorophenylboric acid, 4-chlorophenylboric acid, 2-bromo-phenylboric acid, 3-bromophenylboric acid, 4-bromophenylboric acid, 3,5-difluorophenylboric acid, 2,3-dichlorophenylboric acid, 3,4-dichlorophenylboric acid, 2,4-dichlorophenylboric

acid, 3, 5-dichlorophenylbcric acid, 3, 5-dibromophenylboric acid, 3-chloro-4-fluorophenylboric acid, 3,4,5-trifluorophenylboric acid, 3,4,5-trichlorophenylboric acid, 3,4,5-tribromophenyl-boric acid, 2,3,4,5,6-pentafluorophenylboric acid, 2-tolylboric acid, 3"tolylboric acid, 4-tolylboric acid, 4-ethylphenylboric acid, 3,4-xylylboric acid, mesitylboric acid, 2-trifluoromethylphenylboric acid, 3-trifluoromethylphenylboric acid, 4-trifluoromethylphenylboric acid, 3,5-bis(trifluoromethyl)phenylboric acid, 2-anisylboric acid, 3-anisylboric acid, 4-anisylboric acid, 3-nitrophenylboric acid, 4-nitrophenylboric acid, 3-aminophenylboric acid, 2-carboxyphenylboric acid, 4-carboxyphenylboric acid, 3-acetamidophenylboric acid, 2-forinylphenylboric acid, 3-foirmylphenylboric acid, 4-formylphenylboric acid, 2-methylthiophenylboric acid, 4-methylthiophenylboric acid, 4-biphenylboric acid, 1,2-phenylenediboric acid, 1,3-phenylenediboric acid, 1,4-phenylenediboric acid, 4,4'-biphenyleneboric acid, 1-naphthylboric acid, 2-naphthylboric acid, 2-thienylboric acid, 3-thienylboric acid, 5-chloro-2-thienylboric acid, 2-furylboric acid, 3-furylboric acid, 2-benzofuranylboric acid, 3-benzofuranylboric acid, etc,);
borinic acid derivatives (e.g. dimethylborinic acid, diethylborinic acid, diphenylborinic acid, bis(3,4,5-trifluorophenyl)borinic acid, bis(2,3,4,5,6-
pentafluorophenyl) borinic acid, bis (4-methylphenyl) borinic acid, bis[3,5-bis(trifluoromethyl)-phenyl]borinic acid, etc.);
trimethyl borane, triethyl borane, triphenylborane, tris(3,4,5-trifluorophenyl)borane, tris(2,3,4,5,6-

pentafluorophenyl)borane, tris(4-methylphenyl)borane, tris[3,5-bis(trifluoromethyl)phenyl]borane, tris (3-nitrophenyl)borane, dimethoxyphenylborane, 2-phenyl-l,3,2-dioxabororane, 2-phenyl-4,4,5, 5-tetramethyl-l,3,2-dioxabororane, dimethoxy-(4-methylphenyl)borane, 2-(4-methyl)phenyl-l,3,2-dioxabororane, 2-(4-methyl)phenyl-4,4, 5,5-tetramethyl-l,3,2-dioxabororane, dimethoxy-(3,4,5-trifluorophenyl)borane, 2-(3,4,5-trifluoro)phenyl-l,3,2-dioxabororane, 2- (3,4,5-trifluoro)phenyl-4,4,5,5-tetramethyl-1,3,2-dioxabororane, dimethoxy-(2, 3, 4, 5, 6-pentafluorophenyl)borane, 2-(2,3,4,5,6-pentafluoro)phenyl-1,3,2-dioxabororane, 2-(2,3,4,5,6-pentafluoro)phenyl-4,4,5,5-tetramethyl-1, 3,2-dioxabororane, dimethoxy-(3,5-bistrifluoro-methyl)phenylborane, 2-(3,5-bistrifluoromethyl)phenyl-l,3,2-dioxabororane, 2-(3,5-bistrifluoromethyl)phenyl-4,4,5,5-tetramethyl-1, 3,2-dioxabororane, dimethoxy-(3-nitrophenyl)-borane, 2-(3-nitro)phenyl-l,3,2-dioxabororane, 2-(3-nitro)phenyl-4,4,5,5-tetramethyl-l,3,2-dioxabororane, etc.
In a polymeric boric acid of the formula (5) , n is an integer of 1 or more, and preferably from 1 to 5.
Examples of the polymeric boric acid of the formula (5) include boric acid derivatives or borinic acid derivative, and their anhydrides among the above borane compounds of the formula (4) .
Examples of the boroxine derivative of the formula (6) include trimethylboroxine, triethyl boroxine, triphenyl boroxine, tris(3,4,5-trifluorophneyl)boroxine, tris(2,3,4,5,6-pentafluorophenyl)boroxine, tris(4-

methyl phenyl)boroxine, tris[3,5’
bis(trifluoromethyl)phenyl]boroxine, tris(3-
nitro phenyl)boroxine, etc.
Preferred examples of the borane compound (4), the polymeric boric acid (5) or the boroxine derivative (6) include methylboric acid, n-butylboric acid, phenylboric acid, 3-fluorophenylboric acid, 4-fluorophenylboric acid, 4-chlorophenylboric acid, 4-bromophenylboric acid, 3,5-dichlorophenylboric acid, 3-chloro-4-fluorophenylboric acid, 4-tolylboric acid, 3-trifluoromethyIphenylboric acid, 4-trifluoromethylphenylboric acid, 3,5-
bis(trifluoromethyl)phenylboric acid, 3-anisylboric acid, 3-nitrophenylboric acid, 4-carboxyphenylboric acid, 3-acetamidophenylboric acid, 3-formylphenylboric acid, 4-formylphenylboric acid, 4-methylthiophenylboric acid, 2-naphthylboric acid, 1, 4-phenylenediboric acid, diphenylborinic acid, bis(4-methylphenyl)borinic acid, and their polymeric derivatives (anhydrides); triphenylborane, tris (4-methylphenyl)borane, triphenylboroxine, tris (4-methylphenyl)boroxine, and the like. Particularly preferred compounds are phenylboric acid, 4-tolylboric acid and their anhydrides; triphenylboroxine and tris (4-methyl)phenylboroxine.
Among the borane compounds of the formula (4) , borinic acid derivatives in which one of R% R’ and Rg is a hydroxyl group, or boric acid derivatives in which two of R\ R’ and Rg are hydroxyl groups may also form polymeric derivatives (anhydrides) represented by the formula (5) or (6) . In the present invention.

monomeric compounds, polymeric compounds and their mixtures can be used.
Now, a nitrogen-containing aromatic compound used in the process of the present invention is explained.
A nitrogen-containing aromatic compound used in the process of the present invention is’ usually pyridine, quinoline or isoquinoline, which may optionally be substituted with at least one.substituent selected from a halogen atom (e.g. a fluorine atom, a chlorine atom, a bromine atom and an iodine atom) , a alkyl group (e.g. a methyl group, an ethyl group, a propyl group, an isopropyl group, etc.) and a di alkyl) amino group.
Specific examples of such a nitrogen-containing aromatic
compound include pyridine, quinoline, isoquinoline, 4-
dimethylaminopyridine, 2-picoline, 3-picoline, 4-picoline,
2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 3,4-

autodyne, 3,5-lutidine, 3-chloropyridine, 2-ethyl-3-methylpyridine, 5-ethyl-2-methylpyridine, etc.
Preferred nitrogen-containing aromatic compounds are pyridines which may be substituted with at least one alkyl group, in particular, at least one C1-C3 alkyl group, for example, 2-picoline, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2, 6-lutidine, 2-ethyl-3-methylpyridine, 5-ethyl-2"methylpyridine, etc. Among them, pyridines having a substituent at the 2-position, for example, 5-ethyl-2-methylpyridine are particularly preferred.
The combination of a boron compound and a nitrogen-containing aromatic compound can be the combination of the above

exemplified compounds. In particular, the combination of phenylboric acid and 5-ethyl-2-methylpyridine/ the combination of 4-tolylboric acid and S-ethyl-Z-methyl pyridine, the combination of triphenylboroxine and 5-ethyl-2-methylpyridine, and the combination of tris(4-methylphenyl)boroxine and 5-ethyl-2-methylpyridine are preferred from the viewpoint of overall properties.
The process of the present invention is usually carried out in a solvent. A reaction temperature is usually in the range between about SO’’C and about 250°C, preferably in the range between about 100*’0 and about 200*’C. A reaction time is usually from split second to about 48 hours, preferably from 1 to 24 hours.
Examples of a solvent which may be used in the process of the present invention include aliphatic hydrocarbons (e.g. heptane, octane, ligroin, etc.), aromatic hydrocarbons (e.g. benzene, toluene, ethylbenzene, xylene, mesityl Ne, etc.), halogeneated hydrocarbons (e.g. 1,2-dichloroethane, chlorobenzene, dichlorobenzene, trichlorobenzene, etc.), ethers {e.g. 1,4-dioxane, ethylene glycol dimethyl ether, methyl tert.-butyl ether, etc.), ketones (e.g. methyl isobutyl ketone, cyclohexanone, etc.), acid amides (e.g. N,N-dimethylformamide, etc.), alcohols (e.g. propanol, butanol, amyl alcohol, ethylene glycol, diethylene glycol, etc.), and their mixtures.
The amount of a nitrogen-containing compound is usually from 0.01 to a solvent amount, preferably from 0.1 to 20 moles, per 1 mole of a carboxylic acid derivative of the formula (2) .
The amount of a boron compound is usually from 0.0001 to 5 moles, preferably from 0.001 to 3 moles, in terms of a boron

exemplified compounds. In particular, the combination of phenylboric acid and 5-ethyl"2-methylpyridine, the combination of 4-tolylboric acid and 5"ethyl-2-methylpyridine, the combination of triphenylboroxine and 5-ethyl-2-methylpyridine, and the combination of tris(4-methylphenyl)boroxine and 5-ethyl-2-methylpyridine are preferred from the viewpoint of overall properties.
The process of the present invention is usually carried out in a solvent. A reaction temperature is usually in the range between about 50°C and about 250*’0/ preferably in the range between about 100*’C and about 200*’C. A reaction time is usually from split second to about 48 hours, preferably from 1 to 24 hours.
Examples of a solvent which may be used in the process of the present invention include aliphatic hydrocarbons (e.g. heptane, octane, ligroin, etc.), aromatic hydrocarbons (e.g. benzene, toluene, ethylbenzene, xylene, mesityl Ne, etc.), halogeneated hydrocarbons (e.g. 1,2-dichloroethane, chlorobenzene, dichlorobenzene, trichlorobenzene, etc.), ethers (e.g. 1,4-dioxane, ethylene glycol dimethyl ether, methyl tert.-butyl ether, etc.), ketones (e.g. methyl isobutyl ketone, cyclohexanone, etc.), acid amides (e.g. N,N-dimethylformamide, etc.), alcohols (e.g. propanol, butanol, amyl alcohol, ethylene glycol, diethylene glycol, etc.), and their mixtures.
The amount of a nitrogen-containing compound is usually from 0.01 to a solvent amount, preferably from 0.1 to 20 moles, per 1 mole of a carboxylic acid derivative of the formula (2) .
The amount of a boron compound is usually from 0.0001 to 5 moles, preferably from 0.001 to 3 moles, in tunas of a boron

atom, per 1 mole of a carboxylic acid derivative of the formula (2) .
The carboxylic acid of the formula (2) is a known compound from W098/17632, or can be prepared by the method described in this WO publication.
The carboxylic acid of the formula (2) or its salt has geometric isomers due to the presence of a double bond, optical isomers due to the presence of an asymmetric carbon atom and diastereomers- Any one of such isomers or a mixture thereof may be used in the process of the present invention.
In the process of the present invention, the raw material, a solvent and the like can be charged at once, although it is possible to charge a carboxylic acid derivative of the formula (2), a nitrogen-containing compound and the like by several portions to carry out the reaction.
After the completion of the reaction, the reaction mixture is post-treated, for example, the reaction mixture as such is concentrated, or it is washed with an aqueous solution of an inorganic acid such as hydrochloric acid, sulfuric acid, etc. and the organic layer is dried and concentrated. If necessary, the concentrated product may be purified by recrystallization or with column chromatography to recover a pyridazin-3-on of the formula (1) .
In the process of the present invention, the reaction may be carried out with azeotropic dehydration and/or in the presence of a dehydrator. Examples of such a dehydrator include zeolites such as molecular sieves, silica gel, magnesium sulfate, sodium sulfate, calcium sulfate, copper sulfate, etc. Preferably

zeolites such as molecular sieves, in particular, Molecular Sieve 3A, are used.
When a solid dehydrator is used, it is removed by filtration from a reaction mixture, and then the reaction mixture is subjected to the above post-treatment to recover a pyrida2in-3-one of the formula (1).
Preferred but animating examples of pyridazin-3-on derivatives of the formula (1) are as follows:

EFFECTS OF THE INVENTION
According to the present invention, pyridazin-3-on derivatives having good herbicidal activities can be obtained at a high yield and high purity. EXAMPLES
The present invention will be illustrated by the following examples, which do not limit the scope of the invention in any way.
Example 1
3-Carboxy-2-trifluoromethyl-2-hydroxy"l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydra2one) (Compound 2-2) (5.62 g) / phenylboric acid (0.38 g), Molecular Sieve 4A (powder) (2.70 g), toluene (16.14 g) and 5-ethyl-2-methylpyridine (2.82

g) were charged in a reactor, and stirred at a temperature between 110°C and 115°C for 10 hours. After the reaction mixture was cooled to room temperature, methanol (10.0 g) was added to the mixture, and the supernatant was analyzed with LC by an internal standard method, which is explained below. The yield of 2-(2-fluoro-4-chloro"5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on (Compound 1-2) was 91.2%.
Internal Standard Method
Solutions containing a beforehand isolated objective compound and a standard compound, which is used as the standard of a peak area, in various compositions are prepared, and detected intensities of those solutions are measured by liquid chromatography analysis. Then, a calibration curve is drawn from the weight ratios and the peak area ratios of the objective compound to the standard compound.
Thereafter, the precise amount of the standard compound is added to the specific amount of a reaction mixture after the completion of a reaction, and the mixture is analyzed by liquid chromatography. The concentration of the objective compound is calculated using the calibration curve from the obtained peak area ratio of the objective compound to the standard compound.
In the examples, ethoxybenzene was used as a standard compound.
Examples 2 to 21
The same procedures as those in Example 1 were repeated except that a boric acid derivative shown in Table 1 was used in place of phenylboric acid (0.38 g). Then, the supernatant of the reaction mixture was analyzed by the internal standard

method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on is shown in Table 1.

Example 22
The same procedures as those in Example 11 were repeated except that 0.75 g of 3-nitrophenylboric acid and 3,76 g of 5-ethyl-2-methylpyridine were used. Then, the supernatant of the reaction mixture was analyzed by the internal standard method. The yield of 2-{2-fluoro-4’chloro"5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 91.6%.
Example 23
3-Carboxy-2-trifluoromethyl"2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (9.43 g), phenylboric acid (0.31 g) , Molecular Sieve 3A (powder) (8.97 g) ,

toluene (44.72 g) and 5-ethyl-2-methylpyridine (4,69 g) were charged in a reactor, and stirred at 114""C for 7 hours. After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl"5-trifluoromethylpyrida2in-3-on was 93.5%.
Example 24
The same procedures as those in Example 23 were repeated except that 0.61 g of phenylboric acid and 18.83 g of 5-ethyl-2-methylpyridine were used. Then, the filtrate was analyzed with LC by the internal standard method. The yield of 2- (2-f luoro-4"Chloro-5-hydroxyphenyl) -4-methyl-'5-trifluoromethylpyridazin-3-on was 98.2% .
Example 25
3-Carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (4.62 g), phenylboric acid (0.55 g) , Molecular Sieve 4A (powder) (8,09 g), toluene (80.69 g) and 5-ethyl-2-methylpyridine (2,83 g) were charged in a reactor, and stirred at a temperature between 109*’0 and 112°C for 3 hours. Then, 3-carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-1-(4"Chloro-2-fluoro-5-
hydroxyphenylhydrazone) (4.61 g) and 5-ethyl-2"methylpyridine (1.84 g) were charged. After further 3 hours, 3-carboxy-2" trifluoromethyl-2"hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (4.59 g) and 5"ethyl-2-methylpyridine (1.88 g) were charged. After another 3 hours, 3-carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-

hydroxyphenylhydrazone) (4.61 g) and 5-ethyl-2-methylpyridine (1.85 g) were charged, and the mixture was heated at the same temperature as above for 11 hours.
After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 88.0%.
Example 26
The same procedures as those in Example 25 were repeated except that formed water was isotopically removed. The filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 92.1% .
Example 27
The same procedures as those in Example 2 6 were repeated except that monochlorobenzene (80.76 g) was used in place of toluene. The filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 93.7%.
Example 28
3-Carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (5.65 g), phenylboric acid (0.73 g), Molecular Sieve 3A (powder) (21,52 g), toluene (107.41 g) and 5-ethyl-2-methylpyridine (3.75 g) were charged in a reactor, and stirred at a temperature between 113 and 115°C for 3 hours. Then, 3-carboxy-2-

trifluoromethyl"2-hydroxy-l-butanal-l-{4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (5.63 g) and 5-ethyl-2-methylpyridine (2.51 g) were charged. After further 3 hours, 3-carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (5.63 g) and 5-ethyl-2"methylpyridine (2.50 g) were charged. After another 3 hours, 3-carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l-(4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (5.66 g) and 5-ethyl-2-methylpyridine (2.49 g) were charged, and the mixture was heated at the same temperature as above for 6 hours.
After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on 99.3%.
Example 29
The same procedures as those in Example 23 were repeated except that 2, 6-lutidine (8.10 g) was used in place of 5-ethyl-2-methylpyridine (4.69 g) , and the mixture was stirred at a temperature between 115°C and 116°C for 15 hours. The filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 90.9%.
Example 30
3-Carboxy-2-trifluoromethyl-2-hydroxy-l-butanal-l- (4-chloro-2-fluoro-5-hydroxyphenylhydrazone) (16.68 g), phenylboric acid (0.55 g), Molecular Sieve 3A (powder) (16.24 g) , toluene (80.83 g) and 2-picolin (12.61 g) were charged in

a reactor, and stirred at a temperature between 114 and IIS’'C for 7 hours. After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 91.0%.
Example 31
3"Carboxy-2-trifluoromethyl-2-hydroxy-l-butanal--l- (4-chloro--2-fluoro-5-hydroxyphenylhydrazone) (16.48 g) , triphenylboroxine (0.48 g) , Molecular Sieve 3A (powder) (16.37 g), toluene (84.91 g) and 5-ethyl-2-methylpyridine (17.06 g) were charged in a reactor, and stirred at a temperature between 114 and 115*’C for 6 hours. After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro"4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3-on was 93.6%.
Example 32
The same procedures as those in Example 31 were repeated except that diphenylborinic acid (0.81 g) was used in place of triphenylboroxine (0.48 g) . After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl) -4-methyl-5-trifluoromethylpyridazin-3-on was 93.4%.
Example 33

The same procedures as those in Example 31 were repeated except that triphenylborane (1.14 g) was used in place of triphenylboroxine (0.48 g). After the reaction mixture was cooled to room temperature, the molecular sieve was removed by filtration, and the filtrate was analyzed with LC by an internal standard method. The yield of 2-(2-fluoro-4-chloro-5-hydroxyphenyl) -4-methyl-5--trif luoromethylpyridazin-3-on was 95.4%.
Reference Example 1
3-Carboxy-2-trifluoromethyl-2-hydroxy-1-butanal-l-(4-chloro’2-fluoro-5-hydroxyphenylhydrazone) (0.315 g) was dissolved in the mixture of acetic acid (1.0 ml) and pyridine (1.0 ml) under a nitrogen atmosphere, and stirred at 120°C for 8 hours. After the reaction mixture was cooled to room temperature, it was concentrated under reduced pressure, and the residue was diluted with diethyl ether (100 ml) . Then, the diluted solution was washed with 3N hydrochloric acid (each 20 ml) twice, and saturated sodium bicarbonate (30 ml) once, dried over magnesium sulfate, filtrated and concentrated under reduced pressure. The residue was subjected to column chromatography. Thus, 2-(2"fluoro-4-chloro-5-hydroxyphenyl)-4-methyl-5-trifluoromethylpyridazin-3--on (0.227 g) was obtained.

CLAIMS
1. A method for preparing a pyridazine-S-on derivative of
the formula (1):

wherein R’ is a hydrogen atom or a C1-C3 alkyl group, R’ is a hydrogen atom or a C1-C3 alkyl group, and Q is a phenyl group which may optionally be substituted,
comprising the step of ring closing a carboxylic acid derivative of the fo2:mula (2) :

wherein R’, R’ and Q are the same as defined above, or its salt in the presence of a nitrogen-containing aromatic compound and a boron compound•
2. A process according to claim 1, wherein said boron
compound is at least one compound selected from:
a borane compound of the formula (4):

wherein R’ and R’ are the same and different and represent a hydroxyl group, a C1-C6 alkyl group, a alkoxy group, a phenyl group which may optionally be substituted with at least one substituent selected from a halogen atom, a C1-C4 alkyl group, a

C1-C3 haloalkyl group, a C1-C3 alkoxy group, a nitro group, an amino
group, a carboxyl group, a C1-C3 amide group, a formyl group, a

C1-C3 alkylthio group, a dihydroxylboryl group and a phenyl group that may optionally be substituted with a dihydroxyboryl group,
a naphthyl group which may optionally be substituted with at least one substituent selected from a halogen atom, a C1-C4 alkyl group and a C1-C3 haloalkyl group, a thienyl group which may optionally be substituted with at least one substituent selected from a halogen atom and a C1-C4 alkyl group,
a furyl group which may optionally be substituted with at least one substituent selected from a halogen atom and a C1-C4 alkyl group, a benzofuranyl group the benzene group of which may optionally be substituted with at least one substituent selected from a halogen atom, a C1-C4 alkyl group and a Ci"C3 haloalkyl group, or R'* and R’ together form a ring;
a polymeric boric acid of the formula (5) :

wherein R* is the same as defined above-
3. A process according *to claim 1 or 2, wherein the group

Q in the formulae (1) and (2) is an optionally substituted phenyl group of the formula (3):

wherein X is a hydrogen atom or a halogen atom, Y is a halogen atom, and W is a hydrogen atom or a group of the formula: -ZR’ in which Z is an oxygen atom or a sulfur atom, and R’ is a hydrogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C3-C3 cycloalkyl group, a benzyl group, a alkenyl group, a C3-C6 haloalkenyl group, a C3-C6 alkynyl group, a C3-C6 haloalkynyl group, a cyano-C1-C6 alkyl group, a C1-C6(alkoxyalkyl) group, a C2-C6 (alkoxy thioalkyl) group, a carboxy-C1-C6 alkyl group, (C1-C6 alkoxy) carbonyl-C1-C6 alkyl group, [ alkoxy)-C1-C4 alkoxylcarbonyl-C1-C6 alkyl group, a (C3-C8 cycloalkoxy)carbonyl-C1-C6 alkyl group or a alkoxy)carbonyl-C1-C6 alkyl]oxycarbonyl-C1-C6 alkyl.
4. A process according to claim 3, wherein Z in the formula
(3) is an oxygen atom.
5. A process according to claim 3, wherein W in the formula
(3) is a hydroxyl group.
6. A process according to any one of claims 3 to 5, wherein
X in the formula (3) is a fluorine atom.
7. A process according to any one of claims 3 to 5, wherein
X and Y in the formula (3) are a fluorine atom and a chlorine atom,
respectively.
8. A process according to any one of claims 1 to 7, wherein

R’ and R’ in the formulae (1) and (2) independently represent a hydrogen atom or a methyl group.
9. A process according to anyone of claims 1 to 7, wherein
R’ and R’ in the formulae (1) and (2) are a methyl group and a hydrogen
atom, respectively.
10. A process according to any one of claims 1 to 9, wherein said nitrogen-containing aromatic compound is pyridine which may optionally be substituted with at least one alkyl group.
11. A process according to any one of claims 1 to 9, wherein said nitrogen-containing aromatic compound is 5-ethyl-2-methylpyridine.
12. A process according to any one of claims 1 to 11, wherein said borane compound of the formula (4) is phenyl boric acid or 4-tolylboric acid.
13. A process according to any one of claims 2 to 11, wherein said boroxine derivative of the formula (6) is triphenyl boroxine or tris(4-methylphenyl)boroxine.
14. A process according to any one of claims 1 to 9, wherein said nitrogen-containing compound is 5-ethyl"2-methylpyridine, and said borane compound of the formula (4) is phenyl boric acid.
15. A process according to any one of claims 1 to 9, wherein said nitrogen-containing compound is 5-ethyl-2-methylpyridine, and said boroxine derivative of the formula (6) is triphenyl boroxine.
16. A process according to any one of claims 1 to 15 wherein ‘
said boron compound is used in an amount of from 0.001 to 3 moles,
in terms of a boron atom, per 1 mole of said carboxylic acid /
derivative of the formula (2) or its salt.

17. Process according to any one of claims 1 to 16 wherein
the reaction is carried out with azeotropic dehydration and/or
in the presence of a dehydrator.
18. A process according to claim 17, wherein said dehydrator is a molecular sieve.
19. Aprocess according to claim 18, wherein said molecular sieve is Molecular Sieve 3A.
20. Aprocess according to any one of claims 1 to 19, wherein the reaction is carried out at a temperature of from 100°C to 200°C.

A method for preparing a pyridazm-3-on derivative substantially as herein described and exemplified.

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Patent Number

210771

Indian Patent Application Number

IN/PCT/2001/925/CHE

PG Journal Number

50/2007

Publication Date

14-Dec-2007

Grant Date

08-Oct-2007

Date of Filing

03-Jul-2001

Name of Patentee

M/S. SUMITOMO CHEMICAL COMPANY LIMITED

Applicant Address

5-33, KITAHAMA 4-CHOME, CHUO-KU, OSAKA-SHI, OSAKA 541-0041,

Inventors:

#	Inventor's Name	Inventor's Address
1	MASAO YANAGAWA	2-29-7-B416, OIKE,IBARAKI-SHI, OSAKA 567-0826,
2	MASAHIKO MIZUNO	2-1021, SENRIYAMAMATSUGAOKA,SUITA-SHI, OSAKA 565-0843,
3	YOSHIAKI ODA	1-8-22, SONEHIGASHIMACHI,TOYONAKA-SHI, OSAKA 561-0802,

PCT International Classification Number

C0 7D 237/14

PCT International Application Number

pct/jp99/06842

PCT International Filing date

1999-12-07

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10-350274	1998-12-09	Japan
2	11-172464	1999-06-18	Japan