A variety of 3-vinyl-substituted imidazo[1,5-a]indole derivatives were synthesized by intramolecular Pd-catalyzed cyclization of the title allenamides through either a domino carbopalladation/exo-cyclization process or a novel hydroamination reaction that proceeds smoothly under microwave irradiation. Both the observed pathways involve a π-allyl-palladium(II) complex arising from insertion of the allene group into a palladium(II) species, the latter being formed in situ by the intervention of an aryl iodide or of the N-H group. In both cases, the role of nucleophile is covered by the indole nitrogen.
Tunable Pd-Catalyzed Cyclization of Indole-2-carboxylic Acid Allenamides : Carboamination vs Microwave-Assisted Hydroamination / E.M. Beccalli, A. Bernasconi, E. Borsini, G. Broggini, M. Rigamonti, G. Zecchi. - In: JOURNAL OF ORGANIC CHEMISTRY. - ISSN 0022-3263. - 75:20(2010), pp. 6923-6932. [10.1021/jo101501u]
Tunable Pd-Catalyzed Cyclization of Indole-2-carboxylic Acid Allenamides : Carboamination vs Microwave-Assisted Hydroamination
E.M. BeccalliPrimo
;A. BernasconiSecondo
;E. Borsini;
2010
Abstract
A variety of 3-vinyl-substituted imidazo[1,5-a]indole derivatives were synthesized by intramolecular Pd-catalyzed cyclization of the title allenamides through either a domino carbopalladation/exo-cyclization process or a novel hydroamination reaction that proceeds smoothly under microwave irradiation. Both the observed pathways involve a π-allyl-palladium(II) complex arising from insertion of the allene group into a palladium(II) species, the latter being formed in situ by the intervention of an aryl iodide or of the N-H group. In both cases, the role of nucleophile is covered by the indole nitrogen.
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