Patent ID: 7928240

Claim:
A process for preparing a sulfoxide of formula I or a salt thereof either as a single enantiomer or in an enantiomerically enriched form: Wherein R 1 -R 4 are the same or different and selected from hydrogen, alkyl, alkoxy, halogen, halo-alkoxy, alkylcarbonyl, alkoxycarbonyl, oxazolyl, trifluoroalkyl, or adjacent groups R 1 -R 4 form ring structures which may be further substituted; wherein R 5 and R 7 are same or different and selected from hydrogen, alkyl, alkylthio, alkoxy optionally substituted by fluorine, alkoxyalkoxy, dialkylamino, piperidino, morpholino, halogen, phenylalkyl and phenylalkoxy; R 6 is selected from hydrogen, alkyl, alkylthio, alkoxy optionally substituted by fluorine, alkoxyalkoxy, dialkylamino, piperidino, morpholino, halogen, nitro, phenylalkyl and phenylalkoxy; R 8 is hydrogen or forms an alkylene chain together with R 7 and R 9 and R 10 are same or different and selected from hydrogen, halogen and alkyl; which comprises: a) reacting a mixture of enantiomers of sulfoxide of formula II, differing in configuration at sulfur atom of sulfoxide or a salt thereof: wherein R, X and R 1 -R 4 are as defined for formula I; with a substantially enantiomerically pure compound of formula: R*—Z—Y III wherein R* is a chiral moiety having at least one asymmetric center and at least one asymmetric center in the chiral moiety can have either R or S configuration; Z is and Y is a leaving group to provide diastereomeric compounds of formula IV: wherein R, X, R*, R 1 -R 4 and Z are as defined above; b) separating the diastereomers of formula IV; and c) deprotecting the separated diastereomers with an acid or base to provide a single enantiomer or enantiomerically enriched compound of formula I and optionally preparing the enantiomer formed as the salt.