Dynamic kinetic resolution of an azlactone catalyzed by octahedral chiral-at-metal cobalt(III) complexes under phase-transfer alcoholysis

A family of well-defined octahedral cationic chiral-at- cobalt(III) catalysts based on (R,R)-1,2-cyclohexanediamine and (R,R)-1,2-diphenylethylenediamine has been examined in the dynamic kinetic resolution of an azlactone derived from N-benzoyl-tert-leucine. The reactions catalyzed by 10 mol% of Co^III complexes in the presence of 1 M aqueous NaOH solution under phase-transfer alcoholysis afforded the corresponding benzyl ester of tert-leucine with up to 76% yield and up to 66% enantioselectivity (ee).