Dynamic Kinetic Resolution of a Wide Range of Secondary Alcohols: Cooperation of Dicarbonylchlorido(pentabenzylcyclopentadienyl)ruthenium and CAL-B

The substrate scope in the dynamic kinetic resolution of secondary alcohols was studied by using 31 structurally different alcohols and isopropenyl acetate in the presence of dicarbonylchlorido(pentabenzylcyclopentadienyl) ruthenium and Candida antarctica lipase B (Novozym 435, CAL-B) in toluene. The enzyme and the ruthenium complex were shown to function in a highly compatible manner allowing the conversion of the racemic alcohols into the (R)-acetates in practically theoretical yields and, in most cases, ee values exceeding 99%. The results are fully comparable to those published previously by using earlier reported, state-of-the-art ruthenium-based catalysts for the alcohol racemization. A clear benefit of the dicarbonylchlorido(pentabenzylcyclopentadienyl) ruthenium system, when compared to other (cyclopentadienyl) ruthenium racemization catalysts, is its simple and cost-efficient preparation.