Metallic catalysts for chemo-, regio-and stereoselective reactions, and corresponding precursors
申请人:Sannicolo Francesco
公开号:US20050107248A1
公开(公告)日:2005-05-19
Metallic catalysts of the general formula (I) and their precursors, suitable for chemo- regio- and stereoselective reactions, derived from ortho-bis-(1-phospholanyl)-heteroarenes. The new catalysts are characterized by the presence of two homomorphic phospholanic rings set in adjacent positions of an aromatic pentatomic heterocycle.
Allosteric effects in asymmetric hydrogenation catalysis? Asymmetric induction as a function of the substrate and the backbone flexibility of C1-symmetric diphosphines in rhodium-catalysed hydrogenations
作者:Angharad Baber、Johannes G. de Vries、A. Guy Orpen、Paul G. Pringle、Karl von der Luehe
DOI:10.1039/b607479k
日期:——
The new unsymmetrical, optically active ligands 1,2-C2H4(PPh2)(2′R,5′R-2′,5′-dimethylphospholanyl) (Laa) and 1,3-C3H6(PPh2)(2′R,5′R-2′,5′-dimethylphospholanyl) (Lbb) form complexes of the type [Rh(L)(cyclooctadiene)][BF4] where L = Laa (1a) or Lbb (1b), [PtCl2(L)] where L = Laa (2a) or Lbb (2b) and [PdCl2(L)] where L = Laa (3a) or Lbb (3b). The crystal structures of 2a and 2b show the chelate ligand backbones adopt δ-twist and flattened chair conformations respectively. Asymmetric hydrogenation of enamides and dehydroaminoesters using 1a and 1b as catalysts show that the ethylene-backboned diphosphine Laa gives a more efficient catalyst in terms of asymmetric induction than the propylene-backboned analogue Lbb. The greatest enantioselectivities were obtained with 1a and enamide substrates with ees up to 91%. Substrate-induced conformational changes in the Rh–diphosphine chelates are proposed to explain some of the ees observed in the hydrogenation of enamides.
Probing the Importance of the Hemilabile Site of Bis(phosphine) Monoxide Ligands in the Copper-Catalyzed Addition of Diethylzinc to <i>N</i>-Phosphinoylimines: Discovery of New Effective Chiral Ligands
作者:Isabelle Bonnaventure、André B. Charette
DOI:10.1021/jo800969x
日期:2008.8.1
hemilabile ligand Me-DuPHOS(O) 2 has proven to be a successful ligand for the copper-catalyzed addition of diethylzinc to N-phosphinoylimines. The corresponding α-chiral amines were obtained in high yields (80−98%) and enantiomeric ratios (19.0:1 to 99.0:1 er). Furthermore, this Cu•2 catalytic system has been shown to be effective in the addition of diethylzinc to nitroalkenes and in the reduction of β,β-disubstituted
Enantioselective Hydrogenation with Self-Assembling Rhodium Phosphane Catalysts: Influence of Ligand Structure and Solvent
作者:Mandy-Nicole Birkholz、Natalia V. Dubrovina、Haijun Jiao、Dirk Michalik、Jens Holz、Rocco Paciello、Bernhard Breit、Armin Börner
DOI:10.1002/chem.200601607
日期:2007.7.6
assemble by hydrogen bonding and form chelates. In contrast, synthetic precursors bearing alkoxypyridine appendages are not able to aggregate via intramolecular hydrogen bonds. The nature of self-assembly is dependent on the nature of the P ligand and the solvent used for the hydrogenation (CH2Cl2 vs. MeOH). These features affect the rate of the reaction as well as the enantioselectivity, which varied
Efficient asymmetric hydrogenation with rhodium complexes of C1-symmetric 2,5-dimethylphospholane-diphenylphosphines
作者:Sandeep Basra、Johannes G. de Vries、David J. Hyett、Gayle Harrison、Katie M. Heslop、A. Guy Orpen、Paul G. Pringle、Karl von der Luehe
DOI:10.1039/b404827j
日期:——
optically active ligands 1,2-C(6)H(4)(PPh(2))((R,R)-2,5-dimethylphospholanyl) and the new 1,1'-Fe(C(5)H(4))(2)(PPh(2))((R,R)-2,5-dimethylphospholanyl) form complexes of the type [PtCl(2)(diphos)] and [Rh(diphos)(diene)][BF(4)]. The crystal structure of reveals that only one quadrant is blocked. Asymmetric hydrogenation of acrylic esters and enamides using and as catalysts show that the phenylene-backboned