Structural studies on a Pd allyl complex containing a sugar-based thiophosphine chiral auxiliary

A (1)H, (13)C and (31)P NMR study on the enantioselective allylic alkylation catalyst [Pd(eta(3)-PhCHCHCHPh)(1)]CF(3)SO(3), 2, where 1 = (R)-(2,3,4,6-Tetra-O-acetyl-beta-D-glucopyranose)-1-[(S)-diphenylphosphino)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 nucleophile, (c) the thiosugar moiety is sufficiently close to one end of the 1,3-diphenylallyl ligand that at 233 K there is restricted rotation around the C(allyl)-C(ipso-phenyl) bond (this latter steric interaction is partially reflected in the (13)C chemical shift of the proximate allyl carbon), (d) the ground-state structure reveals a conformation for the six-membered chelate ring in which the methyl group is axial and (e) there is no correlation between the population of the diastereomers in solution and the observed enantiomeric excess.