STRUCTURAL STUDIES ON A PD ALLYL COMPLEX CONTAINING A SUGAR-BASED THIOPHOSPHINE CHIRAL AUXILIARY

A H-1, C-13 and P-31 NMR study on the enantioselective allylic alkylat ion catalyst [Pd(eta(3)-PhCHCHCHPh)(1)]CF3SO3, 2, where 1 = -[(S)-diph enylphosphino)ferrocenyl]ethylthioether, has shown that (a) the major isomer in solution has the exo, syn/syn structure, (b) both steric and electronic effects are operative in directing the incoming nucleophil e, (c) the thiosugar moiety is sufficiently close to one end of the 1, 3-diphenylallyl ligand that at 233 K there is restricted rotation arou nd the C(allyl)-C(ipso-phenyl) bond (this latter steric interaction is partially reflected in the C-13 chemical shift of the proximate allyl carbon), (d) the ground-state structure reveals a conformation for th e six-membered chelate ring in which the methyl group is axial and (e) there is no correlation between the population of the diastereomers i n solution and the observed enantiomeric excess.