The dichotomy between benzene and fulvene formation in palladium-catalyzed domino tricyclizations of 2-bromotetradec-1-ene-7,13-diynes

Abstract

2-Bromotetradec-1-ene-7,13-diynes 1, 5, 12 with different substituents at the acetylenic terminus under palladium catalysis have been found to either yield an angularly bisannelated benzene derivative 3 (79%), or fulvene derivatives of type 5 (52-74%) as well as monoannelated fulvenes 13b-e (32-48%). The mechanisms for all three reaction modes most probably involve intramolecular 5-exo-trig carbopalladations of an intermediate 1,3,5-hexatrienyl-6-palladium bromide intermediate.