Reversibility of palladium-alkyl intermediate formation in deuterioalkoxycarbonylation of 1-hexene

The catalytic pathways of the Pd(PPh3)(2)Cl-2 and Pd(PPh3)(2)Cl-2-SnCl2 catalyzed l-hexene hydroalkoxycarbonylation reaction have been elucidated. Using deuterium labelling, the different reaction products were detected by mass spectral analysis and the deuterium content and its distribution determined by H-1-, H-2- and C-13-NMR methods. The great number of labelled species in residual olefins and carbonylated products does support the assumption that the hydride (Pd-H) route is operating in the mechanism of this system. Alkyl-metal intermediates undergo reversible beta -hydride elimination even at low reaction temperature depending on the catalyst used. (C) 2001 Elsevier Science B.V. All rights reserved.