On the mechanism of the hydroxycarbonylation of styrene with palladium systems

We present a review concerning the mechanism involved in the hydroxycarbony lation of styrene. We discuss the intermediates proposed in the literature, the effect of the acidic medium, the reactivity and kinetics, as well as t he results of theoretical calculations on hydroxycarbonylation and related reactions. We have performed an in situ high-pressure NMR study to obtain m ore insight into the mechanisms that control the regio selectivity and have assessed how this is affected by the phosphorus ligand and the catalyst pr ecursor. We observed palladium hydride and palladium acyl species and we su ggest a catalytic cycle involving palladium hydride, palladium alkyl, and p alladium acyl intermediates.