Preparation and use of C2-symmetric bis(phospholanes): production of .alpha.-amino acid derivatives via highly enantioselective hydrogenation reactions

Abstract

A new class of chiral C 2 -symmetric bis(phospholane) ligands has been prepared and used in rhodium-catalyzed asymmetric hydrogenation reactions. We describe a practical, one-pot procedure which utilizes enantiomerically pure 1,4-diol cyclic sulfates 4 of the preparation of a homochiral series of 1,2-bis(phopholano)ethanes 1 and 1,2-bis(phospholano)benzenes (DuPHOS) 2. Cationic rhodium complexes bearing these new ligands behave as very efficient catalyst precursors for the asymmetric hydrogenation of a broad range of α-(N-acylamino)acrylate (enamide) substrates 5