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

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