Enantioselective, high-yielding synthesis of alcohol-functionalized diphosphanes utilizing asymmetric control with a chiral auxiliary

Enantiomerically pure, alcohol-functionalized diphosphane ligands carrying one phosphorus and three carbon stereo-genie centers were generated from the Diels-Alder reactions of phosphane-functionalized terminal alkenols [3-(diphenyl-phosphanyl)but-3-en-l-ol and 2-(diphenylphosphanyl)prop-2-en-l-ol] with 3,4-dimethyl-l-phenyl-1H-phosphole. The reactions were promoted and controlled by the organoplati-num complex containing ortho-metalated (R)-[1-(dimeth-ylamino)ethyl]naphthalene, and both cycloadditions showed excellent regio- and stereoselectivity under mild conditions with only one enantiomer being formed. The products were isolated in high yield and were characterized by single-crystal X-ray diffraction analysis. Their structures in solution were analyzed by 2D ¹H-¹H ROESY NMR spectroscopy. Subsequent decomplexation and repreparation of the products proved the optical purity of the alcohol-functionalized, chiral diphosphanes formed.