Synthesis of Selenium and Tellurium Bis(thiocarboxylates) and Reaction with Halogen

Abstract

Synthesis of selenium and tellurium derivatives of thiocarboxylic acid which are interesting synthetically and biologically has not been described in literature, except for SeS-aryl (selenothioperoxy)carboxylates and TeS-aryl (telliiirothioperoxy)crboxylates. As a part of our study concerning synthesis of new thio- and dithiocarboxylic acid derivatives, synthesis and reaction of the title's compounds were investigated. Reactions of potassium or piperidinium thiocarboxylates with selenium tetrachloride or sodium selenopentathionate and with tellurium tetrachloride or sodium telluropentathionate were found to give selenium [1] and tellurium bis(thiocarboxylates) [2] in moderate yields. The obtained [1] and [2] are colorless or pale yellow crystals and relatively stable at room temperature. Both [1] and [2] react with chlorine, bromine, and iodine at 0°C to give the corresponding diacyl disulfides. The reaction with, halogen, followed by the addition of piperidinium dithiocarboxylate, afforded the unsymmetrical acyl thioacyl disulfide together with diacyl disulfide and selenium or tellurium bis(dithiocarboxylates). Whereas, the reaction of [2] with bromine at -30°C afforded the crystalline adduct, dibromotellurium bis(thiocarboxylates), which decomposes to give acylthio bromide. On the basis of these, results, possible reaction mechanism, where halogen attacks initially selenium or tellurium atom and then the S-Se or 5-Te bond is cleaved to give acylthio halide (RCOSX, X=halogen) and acylthioseleno or acylthiotelluro halides (RCOSEX, E=Se or Te, X=halogen), was proposed.