ENANTIOMERIC ENRICHMENT OF SULFOXIDES BY PREPARATIVE FLASH CHROMATOGRAPHY ON AN ACHIRAL PHASE

Flash chromatography on silica gel of several sulfoxides of varying ee 's shows a strong enantiomeric fractionation. For example (R)-methyl p -tolyl sulfoxide of 86% ee gives 99% ee (R) in the first fraction and 63% ee (R) in the last fraction, respectively, while (R)-ferrocenyl ph enyl sulfoxide (65% ee) provides (S) enantiomer (19% ee) in the first fraction and (R) enantiomer (94% ee) in the last. fraction. Various as pects of the phenomena are discussed. This method provides a simple pr ocedure to obtain high ee for sulfoxides prepared by asymmetric synthe sis of only modest enantioselectivity.