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Molecules 2016, 21(7), 903; doi:10.3390/molecules21070903

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

1
Organic Synthesis Laboratory and Biological Activity (LSO-Act-Bio), Institute of Chemistry of Natural Resources, Universidad de Talca, Casilla 747, Talca 3460000, Chile
2
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
3
Solid State Chemistry Laboratory, Science Faculty, University of Chile, Santiago, 7800003, Chile
4
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)
View Full-Text   |   Download PDF [1370 KB, uploaded 11 July 2016]   |  

Abstract

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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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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