Synfacts 2009(12): 1330-1330  
DOI: 10.1055/s-0029-1218219
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

Construction of Carbazoles via Pd-Catalyzed Oxidative Coupling of Alkynes

Contributor(s): Victor Snieckus, Toni Rantanen
M. Yamashita, H. Horiguchi, K. Hirano, T. Satoh*, M. Miura*
Osaka University, Japan
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Publication History

Publication Date:
20 November 2009 (online)


The previously reported reaction of benzoic acids with alkynes catalyzed by iridium or rhodium to yield naphthalenes or isocoumarins, respectively, guided the present research: The ­oxidative coupling of heterocycles or heterocyclic carboxylic acids with alkynes. In the case of indoles, the reaction proceeds under palladium catalysis to yield tetrasubstituted N-protected carbazoles in generally good yields. Lower yields were obtained when R² = alkyl or EWG aryl substituents. Thorough optimization and substrate scope studies were carried out. Other hetero­cyclic systems besides indole-3-carboxylic acid were shown to undergo successful coupling reactions. Generally poor yields were observed for R¹ = H rather than R¹ = CO2H.