Palladium-catalyzed reactions of cyclohexadienones: regioselective cyclizations triggered by alkyne acetoxylation.

Regioselective cyclizations of alkyne-tethered cyclohexadienones can be accomplished under palladium catalysis. The cyclization involves an initial Pd-mediated acetoxylation of the alkyne, followed by migratory insertion and protonolysis of the resulting palladium enolate. The predictable regioselectivity of these atom-economical and stereoselective reactions is influenced by developing steric interactions during migratory insertion of a vinyl palladium intermediate.