Synthesis of New 4-Vinyl-1,2,3-Thiadiazoles

Simple and convenient methods for the synthesis of a range of new 1,2,3-thiadiazole derivatives, including ethyl esters, alcohols, and aldehydes, were developed. Moreover, twenty-nine new structurally diverse 4-vinyl-1,2,3-thiadiazoles were successfully synthesized in 18-89 % yield via Knoevenagel condensation. NOESY-experiments were performed for E/Z-assignment of isomeric mixtures. The structure of five of the new vinylic derivatives has been confirmed using X-ray diffraction analysis. Using the example of ethyl (E)-2-cyano-3-(5-(pyrrolidin-1-yl)-1,2,3-thiadiazol-4-yl)acrylate, the possibility of dimerization with the formation of diethyl(1R,2R,3S,4S)-1,3-dicyano-2,4-bis(5-(pyrrolidin-1-yl)-1,2,3-thiadiazol-4-yl)cyclobutane-1,3-dicarboxylate was demonstrated, allowing the first 1,2,3-thiadiazole substituted cyclobutane to be synthesized.