Highly regioselective palladium-catalyzed annulation reactions of heteroatom-substituted allenes for synthesis of condensed heterocycles.

We have developed a highly regioselective synthesis of heterocycles via palladium-catalyzed annulation reaction of heteroatom-substituted allenes. Various aryl halides were reacted and one regioisomer was observed exclusively in all reactions. In addition, subsequent functionalizations of annulated products were carried out using alkyl metal reagents, and the introduction of alkyl moieties was accomplished.