RECENT ADVANCES IN THE ASYMMETRIC DIHYDROXYLATION OF ALKENES

The reaction of osmium tetroxide with alkenes is perhaps one of the most reliable and selective transformations in organic chemistry. In this article, recent advances made in the asymmetric dihydroxylation (ADH) of alkenes have been described. Chiral auxiliaries used for effecting the oxidation of olefins are mainly diamines and cinchona alkaloid derivatives. Complexes derived from osmium tetroxide with diamines do not undergo catalytic turnover whereas dihydroquinidine and dihydroquinine derivatives have been found to be very effective catalysts for the oxidation of a variety of alkenes. Kinetic resolutions of racemic olefins have been achieved. Several crystallographic studies, theoretical calculations and NMR investigations were carried out to determine the actual structure of the catalyst responsible for enantiofacial selection of alkenes. Kinetic and synthetic studies have been reported to illustrate the mechanism. Some of the most recent applications of this newly discovered methodology in the synthesis of natural products are described.