Catalytic, Asymmetric Sulfur Ylide-Mediated Epoxidation of Carbonyl Compounds:  Scope, Selectivity, and Applications in Synthesis

The reaction of sulfur ylides with carbonyl compounds to give epoxides is an important synthetic method. This Account charts the recent advances in rendering this process both asymmetric and catalytic. Two catalytic methods have been developed: the first involving the reaction of a sulfide with an alkyl halide in the presence of a base and aldehyde and the second involving the reaction of a sulfide with a diazo compound or diazo precursor in the presence of a metal catalyst and aldehyde. These catalytic methods coupled with suitable chiral sulfides provide a new catalytic asymmetric epoxidation process for the preparation of epoxides. The scope of the two catalytic processes is discussed together with the factors that influence both relative and absolute stereochemistry. The application of these methods in target-orientated synthesis is also reviewed.