CONVENIENT ASYMMETRIC (SALEN)MN(III)-CATALYZED EPOXIDATION OF UNFUNCTIONALIZED ALKENES WITH HYDROGEN-PEROXIDE USING CARBOXYLATE SALT COCATALYSTS

Asymmetric epoxidation of unfunctionalized alkenes is reported using c hiral (salen)Mn(III) complexes 1-5 together with a carboxylate salt co catalyst in the presence of either aqueous H2O2 or anhydrous urea-H2O2 adduct as oxidant. Several simple soluble salts (acetates, formates, benzoates) were studied all giving good yields of epoxides with modera te to excellent enantioselectivity. For example, 1,1-diphenyl-1-propen e was converted into the corresponding epoxide of 96% ee in 84% yield. Generally, this epoxidation method gave better results than a previou sly described system using nitrogen heterocycles as cocatalysts. (C) 1 998 Elsevier Science Ltd. All rights reserved.