NEW EFFICIENT CATALYSTS FOR ENANTIOSELECTIVE TRANSFER HYDROGENATIONS

New C-2-symmetrical diaminoferrocenyl derivatives 3 and 2-amino(sulfon amido)cyclohexanes 4 were found to be highly active ligands for the ru thenium catalyzed asymmetric transfer hydrogenation of ketones. Contra ry to many existing catalytic systems, the ligands 3 show a high activ ity at 25 degrees C and operate even at -30 degrees C (up to 90 % ee). On the other hand, the slightly less active ligands 4 are very easily prepared and are highly enantioselective at 30 degrees C in HCOOH/Et( 3)N (up to 96 % ee). Copyright (C) 1996 Elsevier Science Ltd