Nickel- and Zinc-Promoted [2 + 2 + 2] Cycloaddition of Diynes and α,β-Enones

The [2 + 2 + 2] cycloaddition of diynes and enones occurred in the presence of both nickel and zinc together. This binary metal-mediated reaction had two interesting features:  (1) a terminally unsubstituted diyne reacted with an enone to give an aromatic compound with the concomitant incorporation of two hydrogen atoms abstracted from an expected 1,3-diene product into another molecule of the starting enone and (2) a trimethylsilyl-substituted diyne reacted with an equimolar amount of enone to regioselectively afford a 1,3-diene, in which the trimethylsilyl group is adjacent to the carbonyl group.