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

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(η3-2-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.