Palladocarbosilane dendrimers as catalysts for the asymmetric hydrovinylation of styrene in supercritical carbon dioxide

摘要

The palladocarbosilane dendrimers 2 and 3, containing the P-stereogenic phosphine [P(2-biphenylyl)PhCH2] fragment, and the model compound Me3Si(P(2-biphenylyl)PhCH2)(PdCl(eta(3)-2-MeC3H4)), 1, were tested as precatalysts in the hydrovinylation of styrene, in supercritical CO2 medium. Na[BARF] was used as a cocatalyst. In all cases, the activity was somewhat less than that observed in CH2Cl2, but the selectivity and enantiomeric excess were excellent and comparable with the results obtained using the conventional solvent. (C) 2008 Elsevier B.V. All rights reserved.