Palladium(0)‐Catalyzed Tandem Cyclization of Allenenes: Direct Construction of Tricyclic Heterocycles through Aromatic CH Activation

Abstract

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 the olefin terminus has proven to be essential for the success of the tandem cyclization. The reaction with heterocyclic aryl halides such as iodopyrazine or 4-bromo-1-methylindole afforded tri- or tetracyclic heteroaromatic products in good yields.

Transition metals in organic synthesis: Highlights for the year 2005

“…Oxidative addition, intermolecular allene insertion, and intramolecular "aromatic-Heck" reaction gave tricyclic heterocycles (Eq. (53)) [494]. A four component reaction using a 2-halobenzaldehyde, 1,2-propadiene, an amino acid, and N-methylmaleiimide to give polycyclic isoquinolines was described (Eq.…”

Construction of Nitrogen‐Containing Heterocycles by CH Bond Functionalization

“…A recent report by the same authors allows the construction of other nitrogen heterocycles using the tandem cyclization of allenenes. [52] An annulation reaction involving direct arylation was developed by Ackermann and co-workers. [53] Carbazoles 73 can be synthesized by a palladium-catalyzed aromatic amination/direct arylation reaction sequence (Scheme 25).…”

Palladium-Catalyzed Bicyclization Processes in the One Step Construction of Heteropolycyclic Ring Systems

“…This innovative strategy was used by Ohno and Tanaka in a cascade reaction involving an allenene and an aryl iodide [51]. This innovative strategy was used by Ohno and Tanaka in a cascade reaction involving an allenene and an aryl iodide [51].…”