Asymmetric synthesis of a P-chiral heteroditopic ligand via chiral metal template promoted cycloaddition between 3,4-dimethyl-1-phenylphosphole and its sulfonated analog

The asymmetric 4+2] Diels-Alder reaction involving 3,4-dimethyl-1-phenylphosphole, DMPP, as the cyclic diene and its P-sulfonated analogue DMPPS as the dienophile was carried out by utilizing the palladium(II) template complex containing ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary. The reaction proceeded regiospecifically and stereoselectively to give corresponding phosphanorbornene ligand as the major product. Throughout the cycloaddition reaction, DMPP functions chemoselectively as the cyclic diene whilst DMPPS assumes the role of dienophile. The absolute stereochemistry of the novel chiral heteroditopic ligand was established by means of single crystal X-ray diffraction analysis.