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

Abstract

This paper describes the reactions of diazomethane with α-alkyl and α-phenyl-substituted ( R S)-β-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.