Asymmetric hydrovinylation and hydrogenation with metal complexes of C <inf>3</inf>-symmetric tris-binaphthyl monophosphites

Neutral allyl-palladium complexes stabilised by bulky tris-binaphthyl monophosphite ligands have been prepared and fully characterised in solution by NMR spectroscopy, which evidenced a dynamic equilibrium between two diastereomeric species. The new allyl-palladium phosphite complexes have been evaluated as catalytic precursors in the asymmetric hydrovinylation of styrene; they show moderate activity and good to excellent chemo- and enantioselectivity depending on the substituent at the ligand 2′-binaphthyl position. Remarkably, the palladium complex bearing the ligand with an adamantyl ester substituent led to 92 % ee toward (R)-3-phenyl-1-butene, which suggests that the ester functionality might provide a secondary hemilabile interaction with the metal, thus favouring the enantioselectivity control. Rhodium(I) complexes formed in situ with the same ligands were further applied in the hydrogenation of dimethyl itaconate, but gave limited activity. The best enantioselectivity (62 %) was achieved with the same ligand that contained the adamantyl ester substituent. Bulky C3-symmetric chiral tris-naphthyl monophosphite ligands have been tested in Pd-catalysed asymmetric hydrovinylation of styrene, giving in some cases very chemo- and enantioselective systems. The same ligands have been used in Rh-catalysed asymmetric hydrogenation of dimethyl itaconate. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.