P-chirogenic MOP phosphines: The crystal structures of oxides, reduction studies and alternate syntheses

ORGN 322

Lee John Higham, lee.higham@ucd.ie1, Eoin F Clarke2, and Declan G. Gilheany, declan.gilheany@ucd.ie1. (1) Chemistry Department, University College Dublin, Belfield, Dublin 4, Ireland, (2) School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
Hayashi's MOP ligand has been highly successful in a variety of asymmetric transformations. In order to improve still further its propensity for chiral induction, we sought to locate additional chirality at the phosphorus centre. We report here our successful synthesis of novel P-chirogenic binaphthyl monophosphines. The ligand preparation was the culmination of investigations into metal-catalysed couplings of racemic secondary phosphine and phosphine oxides with various binaphthyl backbones. We find that the efficacy of the P-C coupling step is strongly dependent on the substitution at phosphorus and furthermore for the oxide couplings, the results of a parallel screening regimen into various reducing agents has highlighted the sensitivity of the tertiary phosphine oxides to epimerization. In one case we also observe tandem P-C bond cleavage leading to a novel secondary phosphine. The use of the ligands in asymmetric catalysis will be discussed.
 

Asymmetric Reactions and Syntheses
1:00 PM-5:00 PM, Monday, 14 March 2005 Convention Center -- Room 11A, Oral

Division of Organic Chemistry

The 229th ACS National Meeting, in San Diego, CA, March 13-17, 2005