Keywords: 3-allylthio-4-methyl-1,2,4-triazole, [1,3]thiazolo [3,2-b][1,2,4]triazolium iodide, [1,2,4]triazolo[5,1-b][1,3]thiazinium iodide, 3-(3-methyl-2-butenyl)thio-4-methyl-1,2,4-triazole, 3-mercapto-4-methyl-1,2,4-triazole, 3-(2-methyl-2-propenyl)thio-4-methyl-1,2,4-triazole, iodocyclization.Derivatives of 3-mercapto-1,2,4-triazoles (1,2,4-triazol-3-thiones) possess a broad spectrum of physiological activity: analgetic, vasodilator, antitumor, bactericidal, and hypotensive effects [1][2][3][4].The reaction of 5-phenyl-, methyl-, and tert-butyl-3-allylthio-1,2,4-triazoles with iodine gave a mixture of products of iodocyclization at the N(2) and N(4) atoms [5,6]. In this work we have synthesized 3-allylthio-(2a), 3-(2-methyl-2-propenyl)thio-(2b), and 3-(3-methyl-2-butenyl)thio-1,2,4-triazole (2c) respectively by the reaction of 3-mercapto-4-methyl-1,2,4-triazole (1) in 2-propanol in the presence of alkali or sodium isopropoxide with 3-bromopropene, 3-chloro-2-methylpropene, and 1-bromo-3-methyl-2-butene, and we have studied their reaction with iodine.It has been established that compound 2a reacted with excess iodine in ether to form a mixture of two products of iodocyclization -6-iodomethyl-3-methyl-5,6-dihydro[1,3]thiazolo[3,2-b][1,2,4]triazolium (3a) and 6-iodo-3-methyl-6,7-dihydro-5H-[1,2,4]triazolo[5,1-b][1,3]thiazinium (4a) polyiodides (a mixture of triiodides and pentaiodides) in a ratio of 0.17:1.00 (according to 1 H NMR spectral data). The salts 3a and 4a were converted into the corresponding monoiodides 3b and 4b. The 1 H NMR spectrum of the mixture of 3b and 4b iodides contains two sets of signals. The signals of the protons of the NCH 2 group of thiazine 4b occur in the 4.60-5.00 region (two doublets of doublets), the signal of proton H-6 in compound 3b forms a multiplet at 5.14 ppm. _______________Celebrating the jubilee of Academician of the Russian Academy of Sciences V. N. Charushin.

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4a,5,6-tetrahydroimidazo[1,5-d][1,3,4]thiadiazinium pentaiodide. Imidazo[1,5-d][1,3,4]thiadiazines are little studied systems. Compounds of this series have been synthesized by treating iminophosphoranes with isothiocyanates [1].We have found that reaction of 2-(5-allylthio-2-amino-6,6,6-trifuoro-1,3,4-triaza-2,4-hexadien-1-yl)-5-trifluoromethyl-1,3,4-thiadiazole (1) with iodine is accompanied by a tandem closure of two heterocyclic systems to form the 7-amino-2-trifluoromethyl-6-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-4,4a,5,6-tetrahydroimidazo[1,5-d][1,3,4]thiadiazinium pentaiodide (2). Evidently, the reaction occurs via the intermediate thiadiazine 3.