Metal-Dependent Reactivity of Electrophilic Platinum Group Metal Lewis Acid Catalysts: Competitive Alkene Dimerization, Intramolecular Friedel−Crafts Alkylation, and Carbonyl-Ene Reactivity

Lewis acid complexes of the type [M{(R)-BINAP}][SbF6]2 (M = Pt, Pd, Ni) catalyze the reaction
between α-methylstyrenes and ethyl trifluoropyruvate to afford products resulting from the expected
carbonyl-ene reactivity as well as tandem alkene dimerization−carbonyl-ene addition and alkene
dimerization−Friedel−Crafts alkylation pathways, the distribution of which depends on the metal
and the substituent attached to the aromatic ring of the styrene substrate. Kinetic studies reveal that the
Lewis acid platinum complex catalyzes the dimerization of 4-chloro-α-methylstyrene much faster than
its palladium counterpart and that the corresponding nickel system has platinum-like reactivity and
selectivity.