BF-Catalyzed Skeletal Rearrangement of 7-En-2-ynones to -Type Cyclic Dienes.

Transition-metal-catalyzed cycloisomerization reactions with skeletal rearrangement of 1,n-enynes to afford cyclic dienes (particularly -cyclization products) have been well studied. However, there are few reports on the nonmetal-catalyzed skeletal rearrangement of enynes and skeletal rearrangement of electron-deficient enynes such as n-en-2-ynones. Here, we describe BF·MeCN-catalyzed synthesis of 3-alkylidenecyclohexenes from 7-en-2-ynones, representing the first nonmetal-catalyzed skeletal rearrangement of 1,6-enynes to -type cyclic dienes.