Asymmetric C-H oxidation of vic-diols to α-hydroxy ketones by a fructose-derived dioxirane:: Electronic effects on the enantioselectivity of oxygen transfer

A mechanistic study on the enantioselective C-H oxidation of vic-diols with the in-situ-generated dioxirane from the fructose-derived ketone 1 is presented. The asymmetrization of meso-configured and the kinetic resolution of racemic vie-diols 2 afforded the optically active alpha-hydroxy ketones 3 in opposite configurations with moderate to good ee values. Significant electronic effects on the enantioselectivity of C-H insertion have been observed, which are explained in terms of the hydrogen-bonded transition-state structures for the concerted C-H oxygen insertion.