Enantioselective Rhodium‐Catalyzed Hydrogenation of Enamides in the Presence of Chiral Monodentate Phosphanes

Abstract

Abstract The rhodium‐catalyzed asymmetric hydrogenation of different acyclic and cyclic N ‐acyl enamides to give N ‐acyl‐protected optically active amines has been examined for the first time in detail in the presence of chiral monodentate 4,5‐dihydro‐3 H ‐dinaphthophosphepines 5a – i . The enantioselectivity is largely dependent on the nature of the substituent at the phosphorus atom and the enamide substrate. Applying optimized conditions up to 95 % ee and catalyst activity up to 2000 h –1 (TOF) have been achieved.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)