Comparative investigation of the regioselectivity in styrene and alpha-methylstyrene hydroalkoxycarbonylation as a function of palladium catalyst structure

Catalytic pathways of the styrene and m-methyl-styrene hydroalkoxycarbonyla tion in the presence of Pd(PPh3)(2)Cl-2 and Pd(PPh3)(2)Cl-2/SnCl2 catalyst precursors have been suggested. As a method, deuterium labelling with EtOD has been applied and it resulted in mixtures of mono- and polydeuterated re action products, detected and determined by NMR methods. Comparative elucid ation of the mechanisms governing these systems does support the assumption that the hydride route is operative. The different behaviour of the metal- alkyl intermediates accounts for the observed strong influence of catalyst and substrate structure on regioselectivity. (C) 1999 Elsevier Science S.A. All rights reserved.