Synthesis and heterocyclization of 8-R-trans-3-cinnamylsulfanyl-5H-[1,2,4]triazino[5,6-b]indoles and methyl 4-(8-R-5H-[1,2,4]triazine[5,6-b]indole-3-sulfanyl)but-2-enoates

Isatin β-thiosemicarbazone and 5-bromoisatin β-thiosemicarbazone were obtained by condensation of aqueous solutions of thiosemicarbazide with isatin and 5-bromoisatin, respectively. Then 5 H -[1,2,4]triazino[5,6- b ]indole-3-thione (1a) and 8-bromo-5 H -[1,2,4]triazino[5,6- b ]indole-3-thione (1b) were synthesized by subsequent cyclization of obtained thiosemicarbazones in heated sodium hydroxide solution. Compounds 1a and 1b were studied in alkylation by trans -cinnamyl chloride and methyl ester of 4-bromocrotonic acid. At that, previously unknown trans -3-cinnamylsulfanyl-5 H -[1,2,4]triazino[5,6- b ]indole (2a) and methyl 4-(8-bromo-5 H -[1,2,4]triazine[5,6- b ]indole-3-sulfanyl)but-2-enoate (3a) were synthesized from compound 1a, 8-bromo- trans -3-cinnamylsulfanyl-5 H -[1,2,4]triazino[5,6- b ]indole (2b) and methyl 4-(8-bromo-5 H -[1,2,4]triazine[5,6- b ]indole-3-sulfanyl)but-2-enoate (3b) were synthesized from compound 1b. The protons of the S-CH2 group form a doublet band in the region of 4.13 and 4.15 p.p.m. in the 1H NMR spectra of compounds 2a and 2b, respectively. Similar protons in the 1H NMR spectra of compounds 3a and 3b resonate at 4.09 and 4.12 p.p.m., respectively. The presence of the bromine atom, which is an electron acceptor, at locant 8 in structures 2b and 3b leads to a slight shift of the signals of aromatic protons of the indole ring, as well as the signal of the NH group proton, to a weaker field in comparison to similar proton signals in the 1H NMR spectra of compounds 2a and 3a that do not contain bromine atoms in the indole fragment. Heterocyclization of S-derivatives of triazino[5,6- b ]indole-3-thiones by iodine and bromine leads to annelation of the six-membered thiazine cycle and formation of new polycondensation systems in the form of 8-R-3-halo-4-R1-2,3,4,11-tetrahydro[1,3]thiazino[3׀,2׀:2,3][1,2,4]triazine[5,6- b ]indolium trihalides. The protons of the SCH2 group in structures of the synthesized trihalides are located next to the asymmetric carbon atom, they are diastereotopic and form doublets of doublets in the region of 3.35-5.36 p.p.m. in the 1H NMR spectra.