Catalytic asymmetric dihydroxylation of C,C double bonds with osmium tetroxide using selenoxides as co-oxidants

Asymmetric dihydroxylation of olefins has been achieved in good yields and ee's using potassium osmate dihydrate (KOsO(OH), the pre-oxidant), (DHQD)PHAL (the chiral ligand), potassium carbonate (the base) and selenoxides (the co-oxidants). Both the yield and the ee proved to be pH dependent, the highest yield and ee being found at almost the same pH values. The rate of the reaction was found to be highly dependent upon the structure of the selenoxide used. Some representative examples involving aminoxides are presented for comparison.