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 stereogenic centers were generated from the Diels-Alder reactions of phosphane-functionalized terminal alkenols [3-(diphenylphosphanyl)but-3-en-1-ol and 2-(diphenylphosphanyl)prop-2-en-1-ol] with 3,4-dimethyl-1-phenyl-1H-phosphole. The reactions were promoted and controlled by the organoplatinum complex containing ortho-metalated (R)-[1-(dimethylamino)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 H-1-H-1 ROESY NMR spectroscopy. Subsequent decomplexation and repreparation of the products proved the optical purity of the alcohol-functionalized, chiral diphosphanes formed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)