Highly diastereoselective methylene transfer from diazomethane to the carbonyl of β-keto sulfoxides.: A general approach to synthetically versatile fluorine-containing chiral building blocks.

This paper describes the reactions of diazomethane with alpha-alkyl and alpha-phenyl-substituted (R-S)-beta-keto sulfoxides bearing difluoro-, trifluoro- and difluorochloromethyl groups on the terminal site, to afford the corresponding diastereo- and enantiomerically pure epoxides. A plausible mechanistic rationale for the origin of the stereochemical preferences in these reactions has been provided. Synthetic versatility of the resultant epoxides has been demonstrated by a series of key transformations of the epoxide ring and the sulfinyl group including ring-opening, reductive desulfurization and syn-elimination reactions. (C) 1998 Elsevier Science Ltd. All rights reserved.