Palladium(0)-catalyzed tandem cyclization of allenenes is described. Treatment of allenenes with an aryl halide, potassium carbonate, and catalytic [Pd(PPh(3))(4)] in dioxane afforded tri- or tetracyclic heterocycles in moderate to good yields through insertion of arylpalladium(II) halide into the allenic moiety, intramolecular carbopalladation, and aromatic C--H bond activation. The substituent on
Thermal [2 + 2] cycloaddition of allenes with an additional multiple bond is described. By simply heating the allenenes or allenynes having a three-atom tether in an appropriate solvent such as dioxane or DMF, the distal double bond of the allenic moiety regioselectively participates in the cycloaddition to form bicyclo[4.2.0]oct-5-ene derivatives in good to excellent yields. In all the reactions of