Palladium-Catalyzed [3+3] Annulation of Vinyl Chromium(0) Carbene Complexes through Carbene Migratory Insertion/Tsuji-Trost Reaction.

Vinyl chromium(0) Fischer carbene complexes were employed as the source of π-allylic palladium species for catalytic [3+3] annulation under palladium catalysis. Mechanistically, this transformation is proposed to involve carbene migratory insertion and intramolecular Tsuji-Trost reaction as the key steps. Substituted six-membered heterocyclic flavonones and quinolines are obtained, depending on the nucleophilic functional group on the coupling partners.