Patent ID: 8513427

Claim:
A process for producing a substituted sulfoxide compound of formula-I or formula-Ia enantiomer thereof, in which, R represents hydrogen atom or lower alkyl group; R′ represents an alkyl group containing 1-6 carbon atoms, optionally interrupted by one or more oxygen atom(s) or haloalkyl, the alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, or butyl and the optionally interrupted alkyl group is selected from 3-methoxypropyl group and the haloalkyl group is selected from trifluoroethyl or difluoromethyl; R″ represents an alkyl group selected from methyl, ethyl or propyl or an alkoxy group; R′″ represents a hydrogen atom or an alkoxy group optionally interrupted by one or more heteroatoms, or a heterocyclic group, the alkoxy group selected from methoxy and difluoromethoxy and the heterocyclic group selected from pyrrole; wherein the process comprising: a) reacting N-oxide of formula-1 with alkali salt of methylmercaptane to obtain thio derivative of formula-2 followed by oxidation using an oxidizing agent to obtain a mesyl derivative of formula-3; b) chlorinating the mesyl derivative of formula-3 in a solvent to obtain a compound of formula-5 or its salt; c) condensing the compound of formula-5 with 2-mercaptobenzimidazole of compound of formula-8 in the presence of a base to obtain a benzimidazole sulfide of formula-6. d) oxidizing the compound of formula-6 in a solvent to obtain benzimidazole sulfoxide of formula-7a; e) stereoselectively oxidizing the compound of formula-6 using an optically active compound in the presence of a metal catalyst and a solvent to obtain the compound of formula-7b; and f) reacting the compound of formula-7a or 7b with an alcohol of formula HOR′ to obtain substituted sulfoxide compound of the formula-I or the formula-Ib respectively.