Chiral macrocyclic salen Mn(III) complexes catalyzed enantioselective epoxidation of non-functionalized alkenes using NaOCl and urea H2O2 as oxidants

Two new chiral Mn(III) macrocyclic salen complexes 1a and 1b were prepared for the enantioselective epoxidation of non-functionalized alkenes. A 5 mol% loading of these catalysts in the presence of pyridine N-oxide as an axial base and sodium hypochlorite or urea hydrogen peroxide adduct as oxidant worked well to give respective epoxides in high yields and ee (up to >95% in selected cases). The catalyst 1b with urea hydrogen peroxide adduct as an oxidant was recovered by precipitation with hexane and was reused up to four times with retention of enantioselectivity. (C) 2010 Elsevier Inc. All rights reserved.