Derivatives of [1,2,4]triazino [5,6-b]indoles possess high biological activity and a wide spectrum of antifungal [1, 2] and antihypoxic activity [3], they are used in prophylaxis and treatment of an extensive index of viruses and have for a long time attracted attention in connection with the search for new antimicrobial and anticancer agents [4].In the literature [3,5] there is information on the synthesis of 3-allylthio-5H-[1,2,4]triazino[5,6-b]indole (1, yield 45%) by the alkylation of 3-mercapto-5H-[1,2,4]triazino[5,6-b]indole (2) with an allyl halide in aqueous NaOH solution. However only the UV spectral data were cited in these papers.In the present work we have synthesized compound 1 in high yield (87%) by the reaction of compound 2 with allyl bromide in a mixture of NaOH-H 2 O-DMSO. Compound 1 was also obtained by a one-pot synthesis from isatin-β-thiosemicarbazone (3) in water without isolating compound 2. The essence of this method is that compound 3 is boiled in aqueous alkali (cyclization with formation of compound 2) and then allyl bromide and triethylbenzylammonium chloride (TEBAC) as phase-transfer catalyst are added to the reaction mixture.We have found that 3-bromomethyl-3,10-dihydro-2H-[1,3]thiazolo[3',2':2,3][1,2,4]triazino[5,6-b]-indolium bromide (4a) was formed on reaction of compound 1 with bromine in DMF.3-Iodomethyl-3,10-dihydro-2H-[1,3]thiazolo[3',2':2,3][1,2,4]triazino[5,6-b]indolium triiodide was formed by the interaction of compound 1 with iodine in chloroform, and was converted to the monoiodide 4b by treatment with NaI in acetone. Halocyclization of 3-allylthio-5-phenyl-1,2,4-triazine also occurs with formation of the dihydrothiazolo[3,2-b][1,2,4]triazinium system [6].
