Synthesis of Enantiomerically Pure 1,2,3,4‐Tetrahydro‐β‐carbolines and N ‐Acyl‐1‐aryl Ethylamines by Rhodium‐Catalyzed Hydrogenation

The rhodium‐catalyzed asymmetric hydrogenation of different enamides, in particular, dihydro‐β‐carboline derivates, was investigated in the presence of chiral phosphorus ligands. Enantioselectivities of up to 99 %  ee were obtained after ligand screening and optimization of the reaction conditions. The scope and limitation of the catalysts were shown in the synthesis of optically active tetrahydro‐β‐carbolines and other benchmark N ‐acyl‐1‐aryl ethylamines.