Enantioselective rhodium-catalyzed hydrogenation of enamides in the presence of chiral monodentate phosphanes

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-3H-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. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)