Enantioselective Diels-Alder Reaction of 3-Diphenylphosphinofuran with 1-Phenyl-3,4-dimethylphosphole and Subsequent Synthetic Manipulations of the Cycloadduct

The asymmetric [4+2] Diels-Alder reaction involving 3-diphenylphosphinofuran as the dienophile and 3,4-dimethyl-1-phenylphosphole, DMPP, as the cyclic diene was carried out by utilizing the platinum(II) template complex containing ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary. The cycloaddition reaction proceeded at 40 degrees C via an intramolecular mechanism in which the cyclic diene and the dienophile were coordinated simultaneously on the chiral platinum template. Two (S-P)-exo cycloadducts were obtained with high stereoselectivity as a P-P bidentate chelate on the platinum template. The chiral naphthylamine auxiliary was subsequently removed by treatment With concentrated hydrochloric acid to form three dichloroplatinum(II) complexes, of which two products were from acid hydrolysis of the vinyl ether. Benzoylation of the hemiacetals gave only one product. The absolute configurations and the coordination properties of the P-chiral cycloadducts have been established by single-crystal X-ray analysis.