Title of Invention

A PROCESS FOR PREPARATION OF N-ALK(EN)OXY(OR ARYLOXY) CARBONYL ISOTHIOCYANATES COMPOUND AND ITS DERIVATIVES

Abstract

A process for the preparation of N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate compound and its derivatives as herein described, said process comprising: a) reacting a haloformate compound of the general formula (I) (I) wherein R1 represents a C1-C5 alkyl radical, a C2-C4 alkenyl radical, or a C6-C10 aryl radical, and X represents a halogen atom, with a thiocyanate of the general formula (II) MSCN (II) wherein M represents an alkali or alkaline earth metal, lead, or NH4, in the presence of an aqueous solvent or an organic solvent, and in the presence of a catalytic amount of a N,N-dialk( en)ylarylamine of the general formula (III) (III) wherein the two R2 each independently of another represent a Ci-Cs alkyl radical or a C3-C6 alkenyl radical, or the two R2 together represent a C5 saturated heterocyclic ring or a C4 saturated heterocyclic ring wherein an oxygen atom may be part of the ring; and R3 represents an aryl group that can be a phenyl, a naphthyl, a substituted phenyl or a substituted naphthyl, to produce a N-alk(en)oxy (or aryloxy)carbonyl isothiocyanate intermediate product of the general formula (IV) (IV) wherein R1 is as defined above in formula (I); and optionally b) reacting the intermediate product (IV) with a compound of the general formula (V) (V) wherein R4 represents a C1 - C10 alkyl radical, a C6 - C10 aryl radical or a C1 - C5 alkoxy radical, and Y represents oxygen, sulfur, or NR5, wherein R5 represents hydrogen or R4, to produce a N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate derivative of the general formula (VI) (VI) wherein R1 is as defined above in formula (I), and R4 and Y are as defined above in formula (V).

Full Text

FORM 2 THE PATENTS ACT 1970 [39 OF 1970] COMPLETE SPECIFICATION [See Section 10] RULE 12 "PROCESS FOR PREPARATION OF N-ALK[EN]OXY [OR ARYLOXY] CARBONYL ISOTHIOCYANATES COMPOUND AND ITS DERIVATIVES. BAYER CORPORATION, of 100 Bayer Road, Pittsburgh, Pennsylvania 15205, United States of America, The following specification particularly describes the nature of the invention and the manner in which it is to be performed:- TECHNICAL FIELD THE INVENTION The field of the present invention is a process for the preparation of n-alk(en)oxy(or aryloxy)carbonyl isothiocyanate compound and its derivatives and particularly to the manufacture of carbonyl isothiocyanates and their derivatives. More particularly, the present invention pertains to an improved process for preparing N-alk(en)oxy(or aryloxy)carbonyl isothiocyanates and their derivatives, wherein the improvement comprises the presence of a N,N-dialk(en)yl-arylamine as a catalyst in the reaction process. BACKGROUND OF THE INVENTION Derivatives of carbonyl isothiocyanates are well known in the art, and various methods for their production are also known in the art. They can be used after further derivatization to prepare 5-alkoxy-substituted l,2,4-triazolinon-3-ones which are usable as intermediates in the commercial preparation of certain agrochemicals. U.S. Patent 4,659,853 discloses a process for producing derivatives of alkoxy, aryloxy and alkene isothiocyanates by reacting a haloformate, an alkali, alkaline earth metal, lead or ammonium thiocyanate and a compound having the formula R1-Y-H wherein R1 is an alkyl, aryl or alkoxy, Y is oxygen, sulfur or N-R2, and R2 is hydrogen or R1 in the presence of a solvent or water and a catalyst. Suitable catalysts include pyridine, quinoline, pyrimidine, pyrazine, quinoxaline and the like. U.S. Patent 4,778,921 describes a process for the preparation of alkoxy and aryloxy isothiocyanates which includes the reaction of a haloformate and an alkali or alkaline earth metal thiocyanate in the presence of water and a catalyst. The catalyst comprises a six- membered mononuclear or ten-membered fused polynuclear aromatic, heterocyclic compound having one or two nitrogen atoms as the only hetero atoms in the ring. U.S. Patent 5,194,673 discloses a process for producing alkoxy and aryloxy 5 isothiocyanates by the reaction of a haloformate and an alkali or alkaline earth metal thiocyanate in the presence of water and a catalyst. A co-catalyst is also used in the process to accelerate the reaction rate, increase product purity, and reduce the adverse effects of impurities in the thiocyanate reactants. 10 In the publication, Chem. Ber. 116, 2044, (1983), it is reported that the use of an aromatic heterocyclic nitrogen catalyst such as pyridine in carbon tetrachloride produced an alkoxythiocarbonyl isothiocyanate wherein the yield was only about 52%. 15 The most prevalent prior art methods comprise (i) the formation of the carbonyl isothiocyanate, (ii) the recovery and purification thereof, and (iii) the final reaction thereof with the appropriate co-reactant to produce the desired derivative. However, the known methods result in carbonyl isothiocyanates of low yield and purity. Thus, there is a need in the art for a process to produce carbonyl isothiocyanates and their 10 derivatives in high yield and purity. BRIEF SUMMARY OF INVENTION The present invention provides a process for the preparation of N-alk(en)oxy(or 35 aryloxy)carbonyl isothiocyanate derivatives which includes reacting a haloformate compound of the general formula (I) O II X—C—O—R1 wherein R1 represents a C1 - C8 alkyl radical, a C2 - C4 alkenyl radical, or a C6 - C10 aryl radical; and X represents a halogen atom; with a thiocyanate of the general formula (II) MSCN (II) wherein M represents an alkali or alkaline earth metal, lead, or NH4, in the presence of an aqueous solvent or in the presence of an organic solvent, and in 1|0 the presence of a catalytic amount of a N,N-dialk(en)ylarylamine of the general formula (III) R2-N-R2 (III) wherein the two R2 each independently of another represent a C1- C5 alkyl radical or a C3 - C6 alkenyl radical, or the two R together represent a C5 saturated heterocyclic ring or a C4 saturated heterocylic ring wherein an oxygen atom may be part of the ring; and R3 represents an aryl group that can be a phenyl, a naphthyl, a substituted phenyl or a substituted naphthyl; to produce a N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate intermediate product of the general formula (IV) O S=C=N-C—O—Ri (IV) wherein R1 is as defined above in formula (I); and reacting a compound of the general formula (V) R4 - Y - H (V) wherein R4 represents a C1 - do alkyl radical, a C6 -Q10 aryl radical or a C1 - C8 alkoxy radical, and Y represents oxygen, sulfur or NR5, wherein R5 represents hydrogen or R4, with the intermediate product (IV) to produce a N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate derivative of the general formula (VI) (VI) wherein R1 is as defined above in formula (I), and R4 and Y are as defined above in formula (V). The first reaction step for the preparation of the carbonyl isothiocyanates of the general formula (IV) taken alone is another embodiment of the instant invention. Accordingly, there is provided a process for the preparation of N-alk(en)oxy(or aryloxy) carbonyl isothiocyanate compound and its derivatives as herein described, said process comprising: a) reacting a haloformate compound of the general formula (I) (I) wherein R1 represents a Ci-Cs alkyl radical, a C2-C4 alkenyl radical, or a C6-C10 aryl radical, and X represents a halogen atom, with a thiocyanate of the general formula (II) MSCN (II) wherein M represents an alkali or alkaline earth metal, lead, or NH4, in the presence of an aqueous solvent or an organic solvent, and in the presence of a catalytic amount of a N,N-dialk( en)ylarylarnine of the general formula (III) wherein the two R2 each independently of another represent a Ci-Cs alkyl radical or a C3-C6 alkenyl radical, or the two R2 together represent a C5 saturated heterocyclic ring or a C4 saturated heterocyclic ring wherein an oxygen atom may be part of the ring; and R3 represents an aryl group that can be a phenyl, a naphthyl, a substituted phenyl or a substituted naphthyl, to produce a N-alk(en)oxy (or aryloxy)carbonyl isothiocyanate intermediate product of the general formula (IV) (IV) wherein R1 is as defined above in formula (I); and optionally b) reacting the intermediate product (IV) with a compound of the general formula (V) R4 - Y - H (V) wherein R4 represents a C1 - C10 alkyl radical, a C6 - C10 aryl radical or a C1 - C8 alkoxy radical, and Y represents oxygen, sulfur, or NR5, wherein R5 represents hydrogen or R4, to produce a N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate derivative of the general formula (VI) O S II II Ri—O—C—NH—O-Y—R4 (VI) wherein R1 is as defined above in formula (I), and R4 and Y are as defined above in formula (V). DETAILED DESCRIPTION OF THE INVENTION The present invention provides a process for producing carbonyl isothiocyanates and their derivatives. In particular, the present process is used to produce N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate derivatives in high yield and purity. The process comprises reacting a haloformate compound of the general formula (I) O X-C—O-R1 (I) wherein R1 represents a C1 - C8 alkyl radical, a C2 - C4 alkenyl radical or a C6 - C10 aryl radical; and X represents a halogen atom, with a thiocyanate of the general formula (II) MSCN (II) wherein M represents an alkali or alkaline earth metal, lead, or NH4, in the presence of an aqueous solvent, and in the presence of a catalytic amount of a N,N-dialk(en)ylarylamine of the general formula (III) wherein the two R each independently of another represent a C1_ C8 alkyl radical or a C3_C6 alk.enyl radical, or the two R2 together represent a C5 saturated heterocyclic ring or a C4 saturated heterocyclic ring wherein an oxygen atom may be part of the ring; and R3 represents an aryl group that can be a phenyl, a naphthyl, a substituted phenyl or a substituted naphthyl; to produce a N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate intermediate product of the general formula (IV) O II S=c=N-C—0—R1 (IV) wherein R is as defined above in formula (I); and reacting a compound of the general formula (V) wherein R4 represents a C1 - C10 alkyl radical, aC6 - C10 aryl radical or a C1 - C8 alkoxy radical, and Y represents oxygen, sulfur or NR5, wherein R5 represents hydrogen or R4, with the intermediate product (IV) to produce a N-alkoxy(or aryloxy)carbonyl isothiocyanate derivative of the general formula (VI) (VI) wherein R.1 is as defined above in formula (I), and R4 and Y are as defined above in formula (V). In another embodiment of the invention the process comprises reacting a haloformate compound of the general formula (I) (I) wherein Rl represents a C1 - C8 alkyl radical, a C2 - C4 alkenyl radical or a C6 -C10 aryl radical; and X represents a halogen atom, with a thiocyanate of the general formula (II) MSCN (II) wherein M represents an alkali or alkaline earth metal, lead, or NH4, in the presence of an organic solvent, and in the presence of a catalytic amount of a N,N-diaIk(en)ylaryIamine of the general formula (III) (III) wherein the two R each independently of another represent a C1 - C5 alkyl radical or a C3 - C6 alkenyl radical, or the two R together represent a C5 saturated heterocyclic ring or a C4 saturated heterocyclic ring wherein an oxygen atom may be part of the ring; and R3 represents an aryl group that can be a phenyl, a naphthyl, a substituted phenyl or a substituted naphthyl; to produce a N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate intermediate product of the general formula (IV) (IV) wherein R1 is as defined above in formula (I); and reacting a compound of the general formula (V) (V) wherein R4 represents a C1 - C10 alkyl radical, a C6 - C10 aryl radical or a C1 - C8 alkoxy radical, and Y represents oxygen, sulfur, or NR , wherein R3 represents hydrogen or R , with the intermediate product (IV) to produce a N-alkoxy(or aryloxy)carbonyl isothiocyanate derivative of the general formula (VI) O S II II Ri—O—C-NH—C—Y-R4 (VI) 5 wherein R is as defined above in formula (I), and R4 and Y are as defined above in formula (V). The process of the present invention may be conducted in a one-pot process. 10 The process according to the invention is generally carried out at atmospheric pres¬sure. In the embodiment of the invention, wherein an aqueous solvent is used in the first 15 reaction step (reaction of the haloformate of general formula (I) with the thiocyanate of general formula (II)), this reaction step is carried out at a temperature of from about -10°C to about 40°C; and preferably at a temperature of from about 0°C to about10°C. 1 0 In the embodiment of the invention, wherein an organic solvent is used in the first reaction step (reaction of the haloformate (formula (I)) with the thiocyanate (formula (II)), this reaction step is carried out at a temperature of from about -10°C to about 116°C; and preferably at a temperature of from about 20°C to about 40°C. ' The haloformate is added to the reaction mixture at a rate such that the temperature of the reaction remains in the desired range. The reaction time for this step in the process of the invention is up to about 16 hours; and preferably the reaction time is from about 1 hour to about 4 hours. The progress of the reaction is monitored by liquid chromatography analysis of the reaction mixture to detennine the amount of unreacted thiocyanate. Suitable haloformates for use in the process of the present invention include the following chloroformates: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl, 2-ethylhexyl, benzyl, phenyl, and allyl chloroformates. In a preferred em¬bodiment, the haloformate is either methyl chloroformate or propyl chloroformate. Suitable thiocyanates for use in the process of the present invention include metal, lead and ammonium thiocyanates. Suitable thiocyanates include sodium, lithium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, and barium thiocyanates. In a preferred embodiment, the thiocyanate is sodium thiocyanate. The reaction of the haloformate and thiocyanate is carried out in the presence of a catalytic amount of a N,N-dialk(en)ylarylamine (formula III), and in the presence of an aqueous solvent or of an organic solvent. Suitable N,N-dialk(en)ylarylamines for use as a catalyst in the reaction of the present invention include N,N-dimefhylaniline, N,N-dimethyl-l-naphthylamine, N,N- dimethyl-p-toluidine, N,N-diethylaniline, N,N-diallylaniline, 1-phenylpiperidine and 4-phenylmorpholine. In a preferred embodiment, the N,N-dialkyl(en)arylamine catalyst is N,N-dimethylaniline. The amount of catalyst present in the reaction mixture is such that it comprises from about 0.1% to about 30% by mole based on the haloformate; and preferably from about 3% to about 9% by mole. Depending on the choice of the embodiment of the instant invention suitable solvents for use in the process of the present invention include either aqueous solvents such as water or include organic solvents. As such suitable organic solvents there may be mentioned alcohols such as methanol, ethanol, propanol, butanol; nitriles such as acetonitrile, propionitrile or butyronitrile; aromatic compounds such as benzene, toluene, xylene; halogenated hydrocarbons such as carbon tetrachloride; tetrahydro-furan; and ketones such as acetone or methyl isobutyl ketone. In a preferred embodiment, the solvent is methyl isobutyl ketone. If an aqueous solvent is used, then there may be mentioned another embodiment of the present invention, wherein, following completion of the reaction between the haloformate and the thiocyanate, an acid such as aqueous hydrochloric acid or aqueous sulfuric acid may be added to the reaction mixture to neutralize the catalyst. In the embodiment of the invention, wherein an aqueous solvent is used, the reaction of the N-alk(en)oxy(or aryloxy)carbonyI isothiocyanate intermediate product of formula (IV) with the compound of formula (V) is carried out at a temperature of from about -10°C to about 100°C, and preferably from about 25°C to about 50°C; for 10 a time period of up to about 16 hours, and preferably from about 2 hours to about 4 hours. In the embodiment of the invention, wherein an organic solvent is used, the reaction of the N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate intermediate product of formula (IV) with the compound of formula (V) is carried out at a temperature of from about -10°C to about 116°C, and preferably from about 25°C to about 50°C, for a time period of up to about 16 hours, and preferably from about 2 hours to about 4 hours. Suitable compounds represented by formula (V) for use in the process of the present invention include alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, amyl alcohols, hexyl alcohols, heptyl alcohols, cyclopentyl alcohol, cyclohexyl alcohol, allyl alcohols, benzyl alcohol; amines such as methylamine, ethylamine, hexylamine, iso- propylamine, isobutylamine, amylamines, cyclohexylamine, octylamine, benzyl- amine, dimethylamine, diethylamine, dipropylamine, dibutylamine, diphenylamine, dibenzylamine, ethylmethylamine, N-methylaniline; mercaptans such as methyl mercaptan, ethyl mercaptan, propyl mercaptan, butyl mercaptan, amyl mercaptans, hexyl mercaptans, benzyl mercaptans, ally] mercaptans and the like. Preferred compounds of formula (V) are methanol and propanol. If an organic solvent is used, then there may be mentioned another embodiment of the present invention, wherein, following completion of the reaction between the N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate intermediate product and the compound of formula (V), an acid such as aqueous hydrochloric acid or aqueous sulfuric acid may be added to the reaction mixture to neutralize the catalyst. The reaction step, which comprises reacting a haloformate compound of the general formula (I) 10 (I) wherein R represents a C1 - C8 alkyl radical, a C2 - C4 alkenyl radical or a C6 -C10 aryl radical; and X represents a halogen atom, with a thiocyanate of the general formula (II) 5 MSCN (II) wherein M represents an alkali or alkaline earth metal, lead, or NH4, in the presence of an aqueous or an organic solvent, and in the presence of a catalytic amount of a N,N-dialk(en)ylarylamine of the general formula (III) (HI) wherein the two R2 each independently of another represent a C1 - C8 alkyl radical or a C3 - C6 alkenyl radical, or the two R2 together represent a C5 saturated heterocyclic ring or a C4 saturated heterocyclic ring wherein an oxygen atom may be part of the ring; and R represents an aryl group that can be a phenyl, a naphthyl, a substituted phenyl or a substituted naphthyl; to produce a N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate intermediate product of the general formula (IV) O S=C=N-C-0-R (IV) wherein R1 is as defined above in formula (I) is itself another embodiment of the instant invention. The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified. EXAMPLES Example 1 - Preparation of MTC, With Neutralization of the Catalyst 7.2 grams (0.06 mole) of 99% pure N,N-dimethylaniline was added to a solution of 86.0 grams (1.04 moles) of 98% pure NaSCN, in 170.5 grams of water, and the mixture was cooled to a temperature of from about 0°C to about 5°C with stirring. About 95.5 grams (1.00 mole) of 99% pure methyl chloroformate was added to the stirred reaction mixture over a period of about 2 hours, maintaining the temperature of the reaction mixture from about 0°C to about 5°C. Following this addition step, the reaction mixture was stirred for about 1 hour. The reaction mixture was then chilled to a temperature of about 0°C. A chilled (about 0°C) solution of 6.18 grams (0.06 mole) of sulfuric acid was dissolved in 174 ml of water, and this solution was added to the reaction mixture (to neutralize the catalyst) over a time period of about 10 minutes. The mixture was then stirred at a temperature of about 0°C for about 15 minutes. The stirring was then stopped and the mixture was allowed to settle for about 15 minutes at a temperature of about 0°C. The mixture separated into an queous phase and an organic phase. The desired N-methoxycarbonyl isothiocyanate product ("MITC") was contained within the organic phase. While maintaining the reaction mixture at a temperature of about 0°C, the lower organic layer (which included the intermediate MITC product) was slowly added to about 277.6 grams (8.68 moles) of methanol, over a time period of about 1 hour, while the temperature of the reaction mixture was maintained between about 30°C and about 40°C. The reaction mixture was then stirred at a temperature of from about 30°C to about 40°C for about 2 hours. The solvent-free purity of N-meth-oxycarbonyl-O-methylthionocarbamate ("MTC") in the reaction mixture at this point was 98.5% (no trace of the isomer MeOOC-SCN was observed using a liquid chromatograph). Analysis by liquid chromatography of the resulting solution of MTC in methanol resulted in a yield of 93.4% based on methyl chloroformate. Example 2 - Preparation of MTC; Without Neutralizing the Catalyst 22.0 grams (0.18 mole) of 99% pure N,N-dimethylaniline was added to a solution of 248.3 grams (3.00 moles) of 98% pure NaSCN, in 595.0 grams of water. The mixture was cooled to a temperature of between about 0°C and about 5°C with stirring. About 274.9 grams (2.88 moles) of 99% pure methyl chloroformate was added to the stirred reaction mixture over a time period of about 2 hours, maintaining the temperature of the reaction mixture between about 0°C and about 5°C. Following addition of the methyl chloroformate, the reaction mixture was then stirred at a temperature of between about 0°C and about 5°C for a period of about 1 hour. The stirring was then stopped and the phases were allowed to separate into an organic and an aqueous phase at a temperature of about 0°C, without prior neu¬ tralization of the catalyst. The organic layer (containing the intermediate "MITC" product) was slowly added to 800.0 grams (25.0 moles) of methanol over a period of about 1 hour, while the temperature of the reaction mixture was maintained between about 30°C and about 40°C. The reaction mixture was then stirred at a temperature of from about 30°C to about 40°C for about 2 hours. Analysis by liquid chromatography of the resulting solution of N-methoxycarbonyl-O-methylthionocarbamate ("MTC") in methanol indicated a yield of 93% based on methyl chloroformate. Example 3 - Preparation of PTC; Without Neutralizing the Catalyst 22.0 grams (0.18 mole) of 99% pure N,N-dimethylaniline was added to a solution of 260.4 grams (3.15 moles) of 98% pure NaSCN, in 640.0 grams of water. The mixture was cooled to a temperature of between about 0°C and about 5°C with stirring. 376.8 grams (3.01 moles) of 98% pure propyl chloroformate was added to the stirred reaction mixture over a period of about 2 hours, maintaining the tem¬ perature of the reaction mixture between about 0°C and about 5°C. Following ad¬ dition of the propyl chloroformate, the reaction mixture was stirred at a temperature of between about 0°C and about 5°C for a period of about 4 hours. The stirring was then stopped and the phases were allowed to separate into an organic phase and an aqueous phase at a temperature of about 0°C, without prior neutralization of the catalyst. The desired N-propoxycarbonyl isothiocyanate product ("PITC") was contained within the organic phase. The organic layer (containing the intermediate PITC product) was slowly added to 540.0 grams (9.0 moles) of propanol over a period of about 1 hour. During this addition step, the temperature of the organic layer was maintained at about 0°C; while the temperature of the resultant reaction mixture was maintained between about 30°C and about 40°C. The reaction mixture was then stirred at a temperature of from about 30°C to about 40°C for about 2 hours. Analysis by liquid chromatography of the resulting solution of N-propoxycarbonyl- O-propylthionocarbamate ("PTC") in propanol indicated a yield of 98% based on propyl chloroformate. Example 4 2) 8.3 grams (0.1 mole) of 98% pure sodium thiocyanate (NaSCN), 0.37 grams (0.003 mole) of the catalyst N,N-dimethylaniline, and 75 ml of methyl isobutyl ketone (MIBK) were charged to a reactor. The reaction mixture was stirred and heated to a temperature of about 85°C. The reaction mixture was made anhydrous by azeotropic distillation of a small amount of the solvent (about 20 ml) under a reduced pressure of about 200 mm of mercury. The reaction mixture was then cooled to room temperature under a nitrogen atmosphere. About 10.5 grams (0.11 mole) of 99% pure methyl chloroformate was added over a time period of about 30 minutes, maintaining the temperature of the reaction mixture between about 25°C and about 40°C. The reaction mixture was then stirred for about 4 hours at room temperature to complete the formation of the intermediate N-methoxycarbonyl isothiocyanate ("MITC"). To convert the MITC intermediate product to N-methoxycarbonyl-O-methyl thiono-carbamate ("MTC"), 6.4 grams (0.20 mole) of methanol was added to the reaction mixture over a time period of about 15 minutes at room temperature. The mixture was then stirred at a temperature of about 50°C for a time period of about 4 hours. The reaction mixture was then cooled to room temperature and the catalyst was neutralized by addition of a mixture of 30 ml of water and 3 ml of concentrated hydrochloric acid. The mixture was stirred for a period of about 15 minutes. The stirring was stopped, the mixture was allowed to settle, and the mixture separated into an organic phase and an aqueous phase. The organic phase (which contained the MTC product) was dried over anhydrous magnesium sulfate and the solvent was removed using a rotary evaporator at a temperature of about 50°C to obtain 13.82 grams of crude MTC as residue. The purity of crude MTC was 98.9% (using liquid chromatography), which translated to a net yield of 91.7% based on the sodium thiocyanate. Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims. WE CLAIM:- 1. A process for the preparation of N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate compound and its derivatives as herein described, said process comprising: a) reacting a haloformate compound of the general formula (I) (I) wherein R1 represents a C1-C5 alkyl radical, a C2-C4 alkenyl radical, or a C6-C10 aryl radical, and X represents a halogen atom, with a thiocyanate of the general formula (II) MSCN (II) wherein M represents an alkali or alkaline earth metal, lead, or NH4, in the presence of an aqueous solvent or an organic solvent, and in the presence of a catalytic amount of a N,N-dialk( en)ylarylamine of the general formula (III) (III) wherein the two R2 each independently of another represent a Ci-Cs alkyl radical or a C3-C6 alkenyl radical, or the two R2 together represent a C5 saturated heterocyclic ring or a C4 saturated heterocyclic ring wherein an oxygen atom may be part of the ring; and R3 represents an aryl group that can be a phenyl, a naphthyl, a substituted phenyl or a substituted naphthyl, to produce a N-alk(en)oxy (or aryloxy)carbonyl isothiocyanate intermediate product of the general formula (IV) (IV) wherein R1 is as defined above in formula (I); and optionally b) reacting the intermediate product (IV) with a compound of the general formula (V) (V) wherein R4 represents a C1 - C10 alkyl radical, a C6 - C10 aryl radical or a C1 - C5 alkoxy radical, and Y represents oxygen, sulfur, or NR5, wherein R5 represents hydrogen or R4, to produce a N-alk(en)oxy(or aryloxy)carbonyl isothiocyanate derivative of the general formula (VI) (VI) wherein R1 is as defined above in formula (I), and R4 and Y are as defined above in formula (V). 2. The process as claimed in claim 1, wherein the haloformate compound is selected from the group of chloroformates consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl, 2-ethylhexyl, benzyl, phenyl, and allyl chloroformate. 3. The process as claimed in claim 1, wherein in step a) the reaction is carried out in the presence of an aqueous solvent at a temperature of from about -10°C to about 40°C and in step (b) the reaction is carried out at a temperature of from about -10°C to about 100°C. 4. The process as claimed in claim 1, wherein in step a) the reaction is carried out in the presence of an organic solvent at a temperature of from about -10°C to about 116°C and in step (b) the reaction is carried out at a temperature of from about -10°C to about 116°C. 5. The process as claimed in claim 1, wherein N,N-dialk(en) ylarylamine is selected from the group consisting of N,N-dimethylamine, N,N-dimentyl-l-naphthylamine, N,N-dimethyl-p-toluidine, N,N-diethylaniline, N,N-diallylaniline, 1-phenylpiperidine, and 4-phenylmorpholine. 6. The process as claimed in claim 1, wherein the N,N-dialk(en)ylarylamine comprises from about 0.1% to about 30% by mole based on the halo formate. 7. The process as claimed in claim 1, wherein the aqueous solvent is water. 8. The process as claimed in claim 1, wherein step a) is carried out in the presence of an aqueous solvent and this step a) further comprises the addition of an acid to the reaction mixture to neutralize the catalyst. 9. The process as claimed in claim 1, wherein step a) is carried out in the presence of an organic solvent and step b) further comprises the addition of an acid to the reaction mixture to neutralize the catalyst. 10. A process for the preparation of N-alk(en)oxy(or aryloxyjcarbonyl isothiocyanate compound and its derivatives substantially as hereinbefore described with reference to the forgoing examples. Dated this 16th day of May, 2000. [SANJAY KUMAR] OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS

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