Engineering polymer-enhanced bimetallic cooperative interactions in the hydrolytic kinetic resolution of epoxides

Through systematic variations of the length of oligo(ethylene glycol)-based linkers and the catalyst density of poly(styrene)-supported cobalt-salen catalysts, we have elucidated an optimal catalyst flexibility and density of polymeric Co-salen catalysts for the hydrolytic kinetic resolution (HKR) of racemic terminal epoxides that follows a bimetallic cooperative pathway. The optimized polymeric catalyst brings the two cooperative Co-salen units to a favorable proximity efficiently and hence displays significantly improved catalytic performance in the HKR compared with its monomeric small molecule analogue. Complex Co(5b), representing the most active poly(styrene)-supported HKR catalyst known so far, can effect the resolution of a variety of epoxides to reach ≥ 98 % ee in 6-24 h with a low cobalt loading of 0.01-0.1 mol%.