Asymmetric C−H Oxidation of vic-Diols to α-Hydroxy Ketones by a Fructose-Derived Dioxirane: Electronic Effects on the Enantioselectivity of Oxygen Transfer
journal contributionposted on 11.09.1999, 00:00 by Waldemar Adam, Chantu R. Saha-Möller, Cong-Gui Zhao
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 vic-diols 2 afforded the optically active α-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.