Synthesis and conversion of thiazinobenzothiazolium salts

Abstract

This paper presents the results of research into the process of electrophilic intramolecular cyclization of 2-cinnamylthiobenzothiazole with halogens and tellurium halides. 2-Cinnamylthiobenzothiazole was prepared by alkylation of mercaptobenzothiazole with cinnamyl chloride in the presence of sodium alcoholate in an alcoholic medium. It was established that as a result of halocyclization of the model 2-cinnamylthiobenzothiazole with an excess of halogen, the thiazine ring is annealed with the formation of 3-halogeno-4-phenyl-3,4-dihydro-2H-[1,3]thiazino[2,3-b][1,3 ]benzothiazolium tribromide trihalides, which are effectively dehalogenated with acetone or sodium sulfite to form monohalides. Halocyclization of cinnamyl thioether of benzothiazole with iodine bromide in chloroform isolated 3-iodo-4-phenyl-3,4-dihydro-2H-[1,3]thiazino[2,3-b][1,3]benzothiazolium bromide, which was converted into 3-iodo-4-phenyl-3,4-dihydro-2H-[1,3]thiazino[2,3-b][1,3]benzothiazolium iodide by ion exchange reaction under the action of potassium iodide in acetone. The corresponding perchlorate was synthesized by the action of sodium perchlorate in methanol on 3-bromo-4-phenyl-3,4-dihydro-2H-[1,3]thiazino[2,3-b][1,3]benzothiazolium bromide. Spectral characteristics (1H NMR) of trihalides, monohalides and perchlorate indicate the preservation of the structure of the thiazinobenzothiazolium cation during ion exchange reactions. Tellurium-induced cyclization of cinnamyl thioether of benzothiazole does not occur. When 2-cinnamylthiobenzothiazole is treated with tellurium dioxide in an excess of halide acid, the nitrogen of the benzothiazole cycle is protonated and aquacomplexes of benzothiazolinium hexahalogenotellurates are formed. Instead, the action of p-alkoxyphenyltellurttrichloride on cinnamyl thioether benzothiazole leads to the formation of molecular complexes in the ratio of thioether:electrophile of 2:1. As a result of the conducted research, potentially biologically active thiazinobenzothiazolium halides were synthesized.