Enantioselective Polymerization of Epoxides: A Highly Active and Selective Catalyst for the Preparation of Stereoregular Polyethers and Enantiopure Epoxides

A chiral, bimetallic cobalt catalyst was discovered that is highly active and enantioselective for epoxide polymerization. The enantiomerically pure catalyst system exhibits a stereoselectivity factor (s = k(fast)/k(slow)) of 370 for propylene oxide, allowing enantiomerically pure epoxide to be recovered in nearly the maximum theoretical yield. In addition, the racemic catalyst forms highly isotactic poly(propylene oxide) in quantitative yield. The catalyst is active and selective for other epoxides, such as 1-butene oxide, 1-hexene oxide, and styrene oxide.