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Synfacts 2010(9): 0994-0994  
DOI: 10.1055/s-0030-1258003
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

Heteroannulation Route to β- and γ-Carbolinones from Indolecarboxamides

Contributor(s): Victor Snieckus, Emilie David
Z. Shi, Y. Cui*, N. Jiao*
Peking University, Beijing and East China Normal University, Shanghai, P. R. of China
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Publication History

Publication Date:
23 August 2010 (online)

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Significance

Reported is the palladium-catalyzed dehydrogenative annulation of indole-2- and 3-carboxamides with symmetrical alkynes leading respectively to β- and γ-carbolinones. The reaction is carried out using Pd(OAc)2 as a catalyst and TBAB as a base at 50 ˚C under air atmosphere for β-carbolinones, whereas it requires a 100 ˚C heating under O2 atmosphere for the
γ-ones. Free (NH)-indoles do not undergo this ­reaction. Both primary and a variety of alkyl-­substituted amides were successfully coupled with symmetrical alkyl and aryl acetylenes. When unsymmetrical alkynes were used, better regio­selectivities (79-89%) were obtained for the β-carbolinones than for the γ-carbolinones (57-67%). A mechanism was suggested without evidence.