Catalyst- and solvent-free synthesis of 2-fluoro-N- (3-methylsulfanyl-1H-1,2,4-triazol-5-yl)benzamide through a microwave-assisted Fries rearrangement : X-ray structural and theoretical studies

Moreno-Fuquen, R. and Arango-Daraviña, K. and Becerra, D. and Castillo, J.-C. and Kennedy, A. R. and Macías, M. A. (2019) Catalyst- and solvent-free synthesis of 2-fluoro-N- (3-methylsulfanyl-1H-1,2,4-triazol-5-yl)benzamide through a microwave-assisted Fries rearrangement : X-ray structural and theoretical studies. Acta Crystallographica Section C: Structural Chemistry, C75 (Part 3). pp. 359-371. ISSN 2053-2296 (https://doi.org/10.1107/S2053229619002572)

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Abstract

An efficient approach for the regioselective synthesis of (5-amino-3-methylsulfanyl- 1H-1,2,4-triazol-1-yl)(2-fluorophenyl)methanone, C10H9FN4OS, (3), from the N-acylation of 3-amino-5-methylsulfanyl-1H-1,2,4-triazole, (1), with 2-fluorobenzoyl chloride has been developed. Heterocyclic amide (3) was used successfully as a strategic intermediate for the preparation of 2-fluoro-N-(3- methylsulfanyl-1H-1,2,4-triazol-5-yl)benzamide, C10H9FN4OS, (4), through a microwave-assisted Fries rearrangement under catalyst- and solvent-free conditions. Theoretical studies of the prototropy process of (1) and the Fries rearrangement of (3) to provide (4), involving the formation of an intimate ion pair as the key step, were carried out by density functional theory (DFT) calculations. The crystallographic analysis of the intermolecular interactions and the energy frameworks based on the effects of the different molecular conformations of (3) and (4) are described.

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