Asymmetric hydroformylation of styrene using rhodium and platinum complexes of diphosphites containing atropisomeric backbones and chiral 1,3,2-dioxaphosphorinane moieties

Diastereomers of 2,2'-bis[4,6-dimethyl-1,3,2-dioxaphosphorinan-2-yloxy]-1,1 '-binaphthyl, R-bis(4R,6R)-1, and S-bis(4R,6R)-2, have been synthesized. Th e solid state structure of S-bis(4S,6S)-1 and the platinum complex [PtCl2(1 )] (3) of its enantiomer pair have been determined. The structure of 3 show s a slightly distorted square-planar geometry. The dihedral angle defined b y the naphthyl rings in 3 is smaller (77.6 degrees(2)) than in the free lig and (103.0 degrees(2)). In the platinum- and rhodium-catalyzed asymmetric h ydroformylation of styrene, the axial chirality in the bridge has been foun d to be determinate for the product configuration with a cooperative effect from the terminal groups. The maximum enantioselectivity (39% ee) and a re markable high regioselectivity (84%) towards branched aldehyde was obtained with platinum system of a matched constellation of the ligand (S-bis(4R,6R )-2). (C) 1999 Elsevier Science S.A. All rights reserved.