Development of useful reactions involving tandem cyclizations based on the novel reactivities of allenic compounds.

This review highlights author's recent study on allenic compounds. In the first section, organocopper-mediated ring-opening reaction of ethynylaziridines and palladium-catalyzed reductive synthesis of allenes including those which are not accessible by other means, are described. In the second section, palladium-catalyzed stereoselective cyclization of allenes and tandem reaction leading to aziridines, pyrrolidines, benzoisoindoles, and cyclopropanes are presented. The final section presents aziridination and medium-ring formation by intramolecular reaction of bromoallenes, which are scarcely investigated until quite recently. The latter reaction is based on our recent discovery that bromoallenes can act as allylic dication equivalents in the presence of a palladium catalyst and alcohol.