Microwave-assisted reactions of nitroheterocycles with dienes. Diels-Alder and tandem hetero Diels-Alder/[3,3] sigmatropic shift

Author: Victoria Gómez, M.; Aranda, A.I.; Moreno, A.; Cossío, F.P.; de Cózar, A.; Díaz-Ortiz, Á.; de la Hoz, A.; Prieto, P.

Description: Diels-Alder cycloaddition of 3-nitro-1-(p-toluenesulfonyl)indole 1 with dienes 2-6 under microwave irradiation in solvent-free conditions gave carbazole derivatives after elimination of the nitro group and in situ aromatization. While 3-nitro-1-(p-toluenesulfonyl)pyrrole 11 afforded indole derivatives, 4-nitro-1-(p-toluenesulfonyl)pyrazole 13 with cyclohexadiene 2 did not afford the expected cycloadduct but instead gave 1-cyclohexen-2-ylpyrazole 16. This process occurred by hydrolysis of the 1-(p-toluenesulfonyl) group, protonation of the diene and nucleophilic addition of the pyrazolate ion, as elucidated by computational studies. Reaction of nitroindole 1 with cyclohexadiene 2 afforded exclusively the endo stereoisomer (10endo) in a tandem hetero Diels-Alder/[3,3] sigmatropic shift, as determined by computational calculations.

Subject Headings: Microwave irradiation; Diels-AlderDiels-Alder/[3,3] sigmatropic shift; Computational studies

Publication year: 2009

Journal or book title: Tetrahedron

Volume: 65

Issue: 27

Pages: 5328-5336

Find the full text : https://www.sciencedirect.com/science/article/pii/S0040402009006267

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Type: Journal Article

Serial number: 2495