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Molecules 2016, 21(7), 903;

Efficient MW-Assisted Synthesis, Spectroscopic Characterization, X-ray and Antioxidant Properties of Indazole Derivatives

Organic Synthesis Laboratory and Biological Activity (LSO-Act-Bio), Institute of Chemistry of Natural Resources, Universidad de Talca, Casilla 747, Talca 3460000, Chile
Grupo/Semillero de Investigación en Compuestos Heterocíclicos, Programa de Química, Facultad de Ciencias Básicas, Universidad del Atlántico, Km 7 Antigua vía Puerto Colombia, Barranquilla 081007, Atlántico, Colombia
Solid State Chemistry Laboratory, Science Faculty, University of Chile, Santiago, 7800003, Chile
Heterocyclic Compounds Research Group, Department of Chemistry, Universidad del Valle, Cali A.A. 25360, Colombia
Author to whom correspondence should be addressed.
Academic Editor: Derek J. McPhee
Received: 9 May 2016 / Revised: 1 July 2016 / Accepted: 5 July 2016 / Published: 9 July 2016
(This article belongs to the Section Green Chemistry)
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A small series of tetrahydroindazoles was prepared, starting from 2-acetylcyclohexanone and different hydrazines using reflux and a focused microwave reactor. Microwave irradiation (MW) favored the formation of the desired products with improved yields and shortened reaction times. This is a simple and green method for the synthesis of substituted tetrahydroindazole derivatives. The in vitro antioxidant activity was evaluated using the DPPH and ABTS methods. In these assays, 2-(4-fluorophenyl)-3-methyl-4,5,6,7-tetrahydro-2H-indazole (3f) showed moderate DPPH decoloring activity, while 3-methyl-4,5,6,7-tetrahydro-1H-indazole (3a), 3-methyl-2-phenyl-4,5,6,7-tetrahydro-2H-indazole (3b) and 2-(4-fluorophenyl)-3-methyl-4,5,6,7-tetrahydro-2H-indazole (3f) were the most active in the ABTS assay. All compounds were well characterized by IR, 1H-, 13C-NMR and GC-MS spectroscopy and physical data, while the structure of 4-(3-methyl-4,5,6,7-tetrahydro-2H-indazol-2-yl)benzoic acid (3e) was also determined by single crystal X-ray analysis. View Full-Text
Keywords: tetrahydroindazole; antioxidant activity; microwave irradiation; green chemistry tetrahydroindazole; antioxidant activity; microwave irradiation; green chemistry

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Polo, E.; Trilleras, J.; Ramos, J.; Galdámez, A.; Quiroga, J.; Gutierrez, M. Efficient MW-Assisted Synthesis, Spectroscopic Characterization, X-ray and Antioxidant Properties of Indazole Derivatives. Molecules 2016, 21, 903.

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