Regioselective and stereoselective cyclizations of cyclohexadienones tethered to active methylene groups.

The cyclization of 2,5-cyclohexadienones tethered to activated methylene groups was studied. The substitution around the cyclohexadienone ring serves to regioselectively direct these cyclizations based primarily on electronic effects. In the case of brominated substrates, these reactions proceed to give highly unusual electron-deficient tricyclic cyclopropanes. By using a Cinchona alkaloid-based phase-transfer catalyst, prochiral cyclohexadienones can be desymmetrized with moderate stereoselectivity.