Patent ID: 7786309

Claim:
A process for preparing a benzimidazole of formula (I): or a pharmaceutically acceptable alkali or alkaline earth salt thereof, the process comprising: (i) oxidizing a sulfide of formula (II): (ii) acylating the sulfide of formula (II) with an alkyl, aryl or aralkyl chloroformate and a base at the 1-N-atom of the sulfoxides's benzimidazole ring of the sulfide of formula (II) to produce a compound of formula (III): (iii) forming a C1 to C4 alkyl alcohol solution by adding the compound of formula (III) to: (a) a C1 to C4 alkyl alcohol, or (b) a solution of an alkali metal alkoxide in a C1 to C4 alkyl alcohol, or (c) a solution of an alkaline earth metal alkoxide in a C1 to C4 alkyl alcohol, and (iv) isolating a benzimidazole sulfoxide or benzimidazole sulfoxide salt of formula I by precipitation wherein ring A is a benzene ring optionally having 1 to 3 substituent(s), which may be the same or different, are each independently selected from (a) a halogen atom, (b) a cyano, (c) a nitro, (d) an alkyl optionally having 1 to 3 substituent(s) selected from a halogen atom, a C 1-6 alkoxy, a C 1-6 alkoxy carbonyl and a carbamoyl, (e) an alkoxy optionally having 1 to 3 substituent(s) selected from a halogen atom, a C 1-6 alkoxy, a C 1-6 alkoxycarbonyl and a carbamoyl, (f) an aryl, (g) an aryloxy, (h) an acyl, (i) an acyloxy and (j) a 5- to 10-membered heterocyclic group, R 1 , R 2 and R 3 are each independently a hydrogen atom; an alkyl group optionally having 1 to 3 substituent(s) selected from a halogen atom, a C 1-6 alkoxy, a C 1-6 alkoxycarbonyl and a carbamoyl; an alkoxy group optionally having 1 to 3 substituent(s) selected from a halogen atom, a C 1-6 alkoxy, a C 1-6 alkoxycarbonyl and a carbamoyl; or a di-C 6-14 arylamino, R 4 is alkyl, aryl or aralkyl, and * denotes a chiral center that may be present as a racemate or in optically enriched form depending on the oxidation process used.