MN-SALEN CATALYZED ASYMMETRIC OXIDATION OF SIMPLE OLEFINS AND SULFIDES

Among the several Mn-salen type catalysts studied, a rationally designed Mn-salen catalyst (14) was found to be the most effective for asymmetric epoxidation of simple olefins, especially cis-disubstituted and trisubstituted olefins conjugated with aryl, alkenyl and alkynyl groups. The mechanism of asymmetrc-inducition of this reaction has been well rationalized by the proposal that olefins approach oxo-metal from the side-on to give a metallaoxetane intermediate, wherein steric and electronic repulsions between the salen ligand and the olefinic substituent dictate the orientation of the incoming olefins and, the intermediate is transformed into epoxides via a radical intermediate. Asymmetric oxidation of sulfides was also found to be effectively catalyzed by Mn-salen catalyst (21). c