NICKEL-PROMOTED AND ZINC-PROMOTED [2-ENONES(2+2]CYCLOADDITION OF DIYNES AND ALPHA,BETA)

The [2 + 2 + 2] cycloaddition of diynes and enones occurred in the pre sence of both nickel and zinc together. This binary metal-mediated rea ction had two interesting features: (1) a terminally unsubstituted diy ne reacted with an enone to give an aromatic compound with the concomi tant 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 trimethylsi lyl group is adjacent to the carbonyl group.