New Enantiopure P,P-Bidentate Bis(diamidophosphite) Ligands. Application in Asymmetric Rhodium-Catalyzed Hydrogenation

Abstract

Two series of new enantiopure bidentate bis(diamidophosphite) ligands with diazaphospholidine and diazaphosphepine heterocyclic backbones were prepared. The ligands have a highly modular structure, which is well suited to the synthesis of a small library of compounds. Preparation was accomplished by the successive addition of enantiomerically pure substituted diamines (N,N′-dibenzylcyclohexane-1,2-diamine (1), N,N′-dimethylcyclohexane-1,2-diamine (2), and N,N′-dimethyl-1,1′-binaphthyl-2,2′-diamine (3)) and enantiomerically pure diols (butanediol (a), cyclohexanediol (b), di-O-isopropylidenethreitol (c), and binaphthol (d)) to phosphorus trichloride. The corresponding bis(diamidophosphite) selenides were prepared, and the 1JPSe values were calculated in order to evaluate the σ-donor ability of the new ligands. The cationic Rh(I) complexes [Rh(COD)(P,P)]BF4 were synthesized with 8 of the 12 new bis(diamidophosphite) ligands. The complexes were used as catalytic precursors for the asymmetric hydrogenation of...