Title of Invention

A PROCESS FOR PREPARING A CHLOROBENZOXAZOLE

Abstract

Process for preparing chlorobenzoxazoles The invention relates to a process for preparing chlorobenzoxazoles of the formula (I), in which R1 , R2 and R4 are as defined in claim 1 and in case (a) R3 = H, halogen, CN, NO2, C1-C5-alkyI, C1-C5-alkoxy, aryl or aryloxy, where each of the 4 lastmentioned radicals is unsubstituted or substituted, or in case (b) R3 = chlorine, which comprises reacting benzoxazoles of the formula (II), in which R1, R2 and R4 are as defined in formula (I) and R3 in case (a) is as defined in formula (I) and R3 in case (b) is hydrogen, in the presence of an acidic catalyst with a chlorinating agent to give the monochlorination product (I) or in case (b) with an excess of the chlorinating agent to give the dichlorination product (I) in which R3 = chlorine.

Full Text

and, alternatively, certain dichlorinations can be carried out in this process. The invention accordingly provides a process for preparing chloro-benzoxazoles of the formula (I), in which R1, R2 and R4 are each, independently of one another, H, halogen, CN, NO2, C1-C5-alkyI, C1-C5-alkoxy, aryl or aryloxy, where each of the 4 lastmentioned radicals is unsubstituted or substituted, and (Case a) R3 = H, halogen, CN, NO2, C1-C5-alkyl, C1-C5-alkoxy. aryl or aryloxy, where each of the 4 lastmentioned radicals is unsubstituted or substituted, or (Case b) R3 = chlorine, which comprises reacting benzoxazoles of the formula (II), in which R1, R2 and R4 are as defined in formula (1) and R3 in case (a) is as defined in formula (I) and R3 in case (b) is hydrogen, in the presence of an acidic catalyst with a chlorinating agent to give the monochlorination product (I) or in case (b) with an excess of the chlorinating agent to give the dichlorination product (I) in which R3 = chlorine. According to the invention, the 2-chloroderivatives of the formula (I) can be prepared selectively in high yield and purity. Moreover, our experiments Description Process for preparing chlorobenzoxazoles The invention relates to the technical field of the processes for preparing intermediates which can be employed for syntheses of active compounds, for example active compounds for crop protection agents or pharmaceuticals. Chlorobenzoxazoles have already attained great importance as intermediates for crop protection agents and pharmaceuticals. Their properties and processes for their preparation are described, inter alia, in DE-A-3207153; EP-A-43573 and GB-A-913910. Using processes from the abovementioned publications, chlorobenzoxazoles can be prepared, for example, from 2-mercapto-1,3-benzoxazoles by exchanging the mercapto group with chlorine using various chlorinating agents. Sulfur chlorides requiring disposal are obtained as byproducts. A further preparation method involves appropriately substituted 1,3-benzoxazol-2-ones which are converted into chlorobenzoxazoles using an excess of phosphorus pentachloride (EP-A-572893; EP-A-141053; DE-A-3406909). In the case of the preparation of 2,6-dichlorobenzoxazole, for example, 6-chlorobenzoxazol-2-one is employed. The reprocessing of the excess of PCI5 employed in this process requires a special effort. It is already known that the unsubstituted thioanalog 1,3-benzothiazole compound can be converted into 2-chlorobenzo-1,3-thiazole by direct chlorination in the presence of chlorination catalysts (DE-A-3234530). However, this selective monochlorination reaction is not known for the analogous benzoxazole; on the contrary. DE-A-2059725 shows that in this case perchlorination occurs in the molecule, without any selectivity in the occupation of the possible substitution sites. An alternative process for preparing chlorobenzoxazoles is required which does not have the disadvantages of the abovementioned processes. Surprisingly, it has now been found that chlorobenzoxazoles can be obtained from benzoxazoles by direct chlorination. Both monochlorinations 1. A process for preparing chlorobenzoxazoles of the formula (I), in which R1, R2 and R4 are each, independently of one another, H, halogen, CN, NO2, C1-C5-alkyl, C1-C5-alkoxy, aryl or aryloxy, where each of the 4 lastmentioned radicals is unsubstituted or substituted, and in case (a) R3 = H, halogen, CN, NO2, C1-C5-aikyl, C1-C5-alkoxy, aryl or aryloxy, where each of the 4 lastmentioned radicals is unsubstituted or substituted, or in case (b) R3 = chlorine, which comprises reacting benzoxazoles of the formula (II), in which R1 , R2 and R3 are as defined in formula (I) and R in case (a) is as defined in formula (I) and R3 in case (b) is hydrogen, in the presence of an acidic catalyst with a chlorinating agent to give the monochlorination product (I) or in case (b) with an excess of the chlorinating agent to give the dichlorination product (I) in which R3 = chlorine. 2, The process as claimed in claim 1, wherein R1 , R2 and R4 in formula (I) are each, independently of one another, H, halogen, CN, NO2, C1-C5-alkyl, C1-C5-haloalkyI, C1-C5-alkoxy, C1-C5- haloalkoxy, phenyl or phenoxy, where each of the 2 lastmentioned radicals is unsubstituted or substituted by one or more radicals selected from the group consisting of halogen, CN, NO2, C1-C4-aikyl, C1-C4-haloalkyl, C1-C4-alkoxy and C1-C4-haloalkoxy, and (Case a) R3 in formula (I) is a radical selected from the group of the radicals possible for R1, R2 and R4 or (Case b) R3 in formula (I) is chlorine. 3. The process as claimed in claim 1 or 2, wherein the compound (I) is 2,6-dichlorobenzoxazole. 4. The process as claimed in any of claims 1 to 3, wherein the reaction is carried out in the presence of an organic or inorganic solvent or neat. 5. The process as claimed in any of claims 1 to 4, wherein the chlodnating agent used is chlorine. SO2CI2, PCI3. PCI5. POCl3, SCl2. S2Cl2, SOCl2 or a mixture of the abovementioned agents, 6. The process as claimed in any of claims 1 to 4, wherein the chlorinating agent used is chlorine in combination with PCI3 or PCI5. 7. The process as claimed in any of claims 1 to 6, wherein the catalysts are employed in an amount of from 0.05 to 10 mol percent, based on the amount of compound of the formula (II) used. 8. The process as claimed in any of claims 1 to 7, wherein the catalyst employed is montmorillonite or a Lewis acid. 9. The process as claimed in any of claims 1 to 8, wherein the catalyst employed is FeCl3 or AICI3, 10. The process as claimed in any of claims 1 to 9, wherein the reaction temperature is from 20 to 200o'C. 11. A process for preparing chlorobenzoxazole substantially A

Documents:

in-pct-2000-093-che-abstract.pdf

in-pct-2000-093-che-claims.pdf

in-pct-2000-093-che-correspondence others.pdf

in-pct-2000-093-che-correspondence po.pdf

in-pct-2000-093-che-description complete.pdf

in-pct-2000-093-che-form 1.pdf

in-pct-2000-093-che-form 26.pdf

in-pct-2000-093-che-form 3.pdf

in-pct-2000-093-che-form 5.pdf

in-pct-2000-093-che-other documents.pdf

in-pct-2000-093-che-pct.pdf

IN-PCT-2000-93-CHE CORRESPONDENCE-OTHERS 13-11-2009.pdf