Asymmetric synthesis of P-chiral diphosphines. Steric effects on the palladium-complex-promoted asymmetric Diels-Alder reaction between a dimethylphenylphosphole and (E/Z)-methyl-substituted diphenylvinylphosphines

Three optically pure P-chiral diphosphines were efficiently synthesized by the palladium-complex-promoted asymmetric Diels-Alder reaction of 1-phenyl-3,4-dimethylphosphate with diphenylvinylphosphine, (E)-diphenyl-1-propenylophosphine and (Z)-diphenyl-1-propenylophosphine, respectively. (S)-(1-(dimethyllamino)ethyl)naphthalene was used as the chiral auxilliary in the reaction. The diphosphines were observed to be highly air-sensitive in the free ligand and powerful sequesters of group 8 metals.