Aggarwal, RanjanaSharma, ShilpaSanz, DionisiaClaramunt, Rosa M.Delgado, PatriciaTorralba, M. CarmenTorralba Martínez, María Del Carmen2025-01-232025-01-232024-11-08RSC Adv., 2024,14, 3558510.1039/d4ra05436ahttps://hdl.handle.net/20.500.14352/115833The present study reports some fascinating results of Hantzsch's [3 + 2] cyclic condensation of α-bromo-1,3-diketones, a tri-electrophilic synthon generated in situ by bromination of 1,3-diketones using the mild brominating reagent NBS with trinucleophilic N-substituted thioureas. Interestingly, out of a total of 20 combinations, 10 resulted in the exclusive formation of the desired 2-(N-arylamino)-5-acyl-4-methylthiazoles regioselectively, seven led to the formation of unexpected 2-(N-acylimino)-3-N-aryl-4-methylthiazoles through an interesting C–N acyl migration, and three furnished a mixture consisting of both products. The regioselectivity pattern of the two products may be attributed to a greater electrophilicity of the carbonyl carbon of the acetyl group than that of the acyl group towards both nitrogens of thiourea. The structures of the thiazole derivatives were unambiguously assigned using 1H-NMR, 13C-NMR, and rigorous heteronuclear 2D-NMR [(1H–13C) HMQC and (1H–13C) HMBC] spectroscopic techniques. The outcomes of the spectroscopic experiments were further concurred through X-ray crystallographic studies, and a plausible mechanism for acyl migration was proposed for the formation of the unexpected rearranged product.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/journal articlehttps://doi.org/10.1039/d4ra05436ahttps://pubs.rsc.org/en/journals/journal/RAopen access2332576HeterocycloRegiselectivitySubstituted 2-aminothiazolesCrystallographyCiencias2303 Química Inorgánica2303 Química Inorgánica