Readily Available Ruthenium Complex for Efficient Dynamic Kinetic Resolution of Aromatic α-Hydroxy Ketones

A ruthenium complex formed from commercially available [Ru(p-cymene)Cl-2](2) and 1,4-bis(diphenylphosphino)butane catalyzes the racemization of aromatic alpha-hydroxy ketones very efficiently at room temperature. The racemization is fully compatible with a kinetic resolution catalyzed by a lipase from Pseudomonas stutzeri. This is the first example of dynamic kinetic resolution of alpha-hydroxy ketones at ambient temperature in which the metal and enzyme catalysts work in concert in one pot at room temperature to give quantitative yields of esters of alpha-hydroxy ketones with very high enantioselectivity.