Synthesis of novel fluorine- and iodine-containing [1,2,4]triazolo[3,4-b][1,3]thiazines based 3-(alkenylthio)-5-(trifluoromethyl)-4H-1,2,4-triazole-3-thiols

In this paper we report the synthesis of novel S-alkenyl derivatives of 5-(trifluoromethyl)-4H-1,2,4-triazole-3-thiol via alkenation reaction with different alkenyl halides. Reaction between the resulting S-alkenation products and iodine proceeds regiospecifically to give new fused fluorine- and iodine-containing [1,2,4]triazolo[3,4-b][1,3]thiazine heterocyclic systems. The structure of synthesized compounds was confirmed by mass spectra, IR, 1H, 13C and 19F NMR spectroscopy including 2D 1H–13C HSQC, 1H–1H COSY, 1H–13C HMBC correlations, elemental analysis and single-crystal X-ray diffraction study.

Graphical abstractNovel fluorine- and iodine-containing [1,2,4]triazolo[3,4-b][1,3]thiazine heterocyclic systems were easily synthesized from iodination of 3-(alkenylthio)-5-(trifluoromethyl)-4H-1,2,4-triazole-3-thiols obtained via alkenation reaction with different alkenyl halides. Iodocyclization of S-methallyl derivative proceeded in unexpected path via thiazine ring closure.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► S-alkenation of 5-(trifluoromethyl)-4H-1,2,4-triazole-3-thiol. ► Regiospecifical iodination of the S-alkenyl derivatives obtained. ► Facile synthesis of new fluorine- and iodine-containing [1,2,4]triazolo[3,4-b]thiazines.