Rearrangement of --Butanesulfinyl Enamines for Synthesis of Enantioenriched α-Hydroxy Ketone Derivatives.

Treating chiral --butanesulfinyl ketimines with potassium hexamethyldisilazide (or potassium -butoxide) and methyl triflate gives -methylated --butanesulfinyl enamine intermediates that undergo stereoselective [2,3]-rearrangement to afford α-sulfenyloxy ketones with excellent enantiopurities. This cascade of enamination--methylation-rearrangement was even used to generate acyclic tertiary α-hydroxy ketones bearing two α-substituents showing negligible differences in bulkiness, such as methyl and ethyl groups.