Asymmetric hydrovinylation of styrene applying cationic allyl palladium complexes of a P-chiral ligand Prof. Dr. Dr. hc Friedrich Asinger on the occasion of his 90th birthday

摘要

Cationic allyl palladium complexes of the diasteriomerically pure P-chiral ligand tert-butyl(menthyl-O)phenylphosphinite 1 were prepared from [(eta(3)-C3H5)PdI](2) and [(eta(3)-C3H5)Pd(cod)]X. Ligand 1 and the complex [(eta(3)-C3H5)PdI(1)] 9 were characterized by X-ray crystallography. The absolute configuration at the phosphorus center of 1 was determined to be (S) for the (-)-menthol derivative. Crystals are orthorombic, space group P2(1)2(1)2(1), a = 8.505(3) Angstrom b = 10.82(1) Angstrom, c = 23.297(3) Angstrom, V = 2144(2) Angstrom(3). Complex 9 shows distorted square planar geometry. Crystals are trigonal, space group P3(2), a = 13.980(5) Angstrom, c = 11.292(3) Angstrom, V = 1911(2) Angstrom(3). Asymmetric codimerization of styrene and ethylene was successfully applied. High enantioselectivities of up to 86% ee have been obtained at room temperature. The codimer 3-phenylbut-1-ene (3PB1) was formed in high selectivity (up to 96%) with only small amounts of the isomerization products E- and Z-2-phenylbut-2-ene. By addition of various coordinating solvents, the catalyst system was efficiently stabilized. Variation of the complex counter anion had significant effect on enantioselectivity. (C) 1998 Elsevier Science S.A. [References: 29]