A BIOMIMETIC CATALYST FOR THE ASYMMETRIC EPOXIDATION OF UNFUNCTIONALIZED OLEFINS WITH HYDROGEN-PEROXIDE

A chiral pentadentate dihydrosalen ligand, carrying an imidazole group as the fifth donor, was synthesized in enantiomerically highly enrich ed form. The corresponding manganese(III) complex catalyzed the epoxid ation of olefins with dilute hydrogen peroxide. With 1,2-dihydronaphth alene as substrate and 10 mol-% of catalyst, enantiomeric excess up to 64 % was achieved. The latter value is the highest so far reported fo r a metal-catalyzed asymmetric epoxidation employing hydrogen peroxide as the terminal oxidant.