Nickel-catalyzed multicomponent coupling reaction using ynones

Conjugate addition of Me3SiCN to ynones is smoothly catalyzed by Ni(cod)2 to give β-cyano-silyloxyallenes quantitatively. Subsequent treatment of the silyloxyallenes with N-bromo succinimide (NBS) provides the tetrasubstituted α-bromo-β-cyanoenones in high yields (up to 95 %) with excellent Z-selectivity (E/Z = up to >1/99). X-ray crystallographic analysis shows a bent structure of the α-bromo-β-cyanoenone due to deconjugation of the π-bond and the carbonyl group. Furthermore, three-component coupling reactions of ynones, dialkylzinc, and alde-hydes are catalyzed by Ni(cod)2 to provide tetrasubstituted olefins.