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Palladium-Catalyzed Annulation of Allenes with Indole-2-carboxylic Acid Derivatives: Synthesis of Indolo[2,3-c]pyrane-1-ones via Ar–I Reactivity or C–H Functionalization
- Suresh, R. Rama, Swamy, K. C. Kumara
- Journal of organic chemistry 2012 v.77 no.16 pp. 6959-6969
- acids, carbon-hydrogen bond activation, catalytic activity, chemical reactions, chemical structure, organic chemistry, organic compounds, palladium, regioselectivity
- Two methodologies, one involving Ar–I reactivity and the other through C–H functionalization, for the formation of indolo[2,3-c]pyrane-1-ones via the corresponding allenes, are presented. A highly efficient approach to indolo[2,3-c]pyrane-1-one derivatives through the Pd-catalyzed regioselective annulation of allenes with 3-iodo-1-alkylindole-2-carboxylic acids is described. This method is fairly general for a wide range of allenes affording the respective indolo[2,3-c]pyrane-1-ones in good to excellent yields. In addition, a Pd(II)-catalyzed oxidative coupling of indole-2-caboxylic acid derivatives with allenes via direct C–H functionalization to afford the corresponding indolo[2,3-c]pyrane-1-ones in moderate to good yields has been developed.