PROBING THE NATURE OF H-2 ACTIVATION IN CATALYTIC ASYMMETRIC HYDROGENATION

Despite many years of intensive study, the natures of turnover-limitin g and enantio-determining steps in catalytic asymmetric hydrogenation of prochiral enamides are poorly understood. An intriguing set of stud ies involving isotopic labeling distributions in catalytic enamide hyd rogenation reactions were reported by Brown and Parker (Organometallic s, 1 (1982) 950-956) more than a decade ago. In this paper we report t he results of studies re-examining the application of isotopic probes to the catalytic hydrogenation enamides. These results provide some in sights into the nature of the H-2, activation step in enamide hydrogen ation. (C) 1998 Elsevier Science S.A.