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

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