Phosphine−Substrate Recognition through the C−H···O Hydrogen Bond: Application to the Asymmetric Pauson−Khand Reaction
作者:Jordi Solà、Antoni Riera、Xavier Verdaguer、Miguel A. Maestro
DOI:10.1021/ja053653u
日期:2005.10.1
A unique methine moiety attached to three heteroatoms (0, P, S) and contained in the PuPHOS and CamPHOS ligands serves as a strong hydrogen-bond donor. Nonclassical hydrogen bonding of this methine with an amido-carbonyl acceptor provides a completely diastereoselective ligand exchange process between an alkyne dicobalthexacarbonyl complex and a phosphine ligand. This weak contact has been studied by means of X-ray analysis, H-1 NMR, and quantum mechanical calculations and revealed that the present interaction falls in the range of strong C-(HO)-O-...= C bonds. The hydrogen-bond bias obtained in the ligand exchange process has been exploited in the asymmetric intermolecular Pauson-Khand reaction to yield the corresponding cyclization adducts in up to 94% ee.