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

作者：Bravo Maritza J; Ceder Rosa M; Muller Guillermo; Rocamora Merce^*

来源：Organometallics, 2013, 32(9): 2632-2642.

DOI：10.1021/om400119q

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%26apos;-dibenzylcyclohexane-1,2-diamine (1), N,N%26apos;-dimethylcyclohexane-1,2-diamine (2), and N,N%26apos;-dimethyl-1,1%26apos;-binaphthyl-2,2%26apos;-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 (1)J(PSe) values were calculated in order to evaluate the (sigma-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 benchmark substrates, namely methyl alpha-acetamidoacrylate (4), methyl (Z)-alpha-acetamidocinnamate (5), and dimethyl itaconate (6). The influence of the nature of both the terminal and bridging fragments of the bis(diamidophosphite) ligands on the asymmetric induction is discussed. Most proved to be effective catalysts for the process, attaining total conversion and excellent enantioselectivity (%26gt;99% ee) with the complex containing the (R;R-al,R-al;R)-3c ligand in the hydrogenation of the three substrates. The best performing catalytic precursor [Rh(COD)-((R;R-al,R-al;R)-3c)]BF4 was tested in the hydrogenation of selected cyclic enamides (7-9) and beta-acetamidoacrylate (10).

• 出版日期2013-5-13