Dramatic Enhancement of Reactivity of Organosilicon Compounds Induced by Complexation of Bis(allyl)silanes with Fluoride Ion

New type of fluoride ion catalyzed allylation agent (1a, 1b), allenylation agent (9, 10), and alkynylation agent (17) can be successfully utilized for various carbonyl substrates. The rate acceleration is ascribable to the shift of equilibrium to the chelate complexes with Bu4NF by the favorable chelation of bis(silyl) compounds toward the fluoride ion. The 19F NMR spectrum (ethyl trifluoroacetate as external standard) of a mixture of 1a and Bu4NF in CDCl3 showed two peaks at δ −81.75 and −77.67 (integration ratio∼9:1). The large signal corresponds to the original peak of Bu4NF and the small one might be ascribed to the chelate complex [B] between 1a and Bu4NF. The fluoride ion mediated reaction of bis(crotyldimethylsilyl)methane (7) with benzaldehyde was examined and the only γ-adduct 8 was obtained regioselectively.