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,S-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.