PLATINUM-CATALYZED OXIDATIONS WITH HYDROGEN-PEROXIDE - THE (ENANTIOSELECTIVE) EPOXIDATION OF ALPHA,BETA-UNSATURATED KETONES

The catalytic epoxidation of cl,P-unsaturated ketones with hydrogen pe roxide catalyzed by a variety of (P-P)Pt(CF3)(solv)(+) and (P-P)Pt(2-v an) complexes (P-P = a variety of diphosphines, including chiral dipho sphines; 2-van = the bis anion of 2-vanillin) is reported. The reactio n can be carried out at room temperature under mild conditions and is moderately selective. Loss of chemical selectivity is related to the a cidity of the medium with both classes of catalysts. The enantioselect ive transformation can be easily accomplished with chiral diphosphine modified catalysts, but a significant loss of enantioselectivity is ob served during the course of the reaction. If the reaction is carried o ut stoichiometrically with the use of (P-P)Pt(CF3)(OOH) oxidants, the ee can be as high as 63% and stable with time.