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Synthesis of 1,2,3-thiadiazoles

A facile and practical TBAI-catalyzed reaction between N-tosyl hydrazones and sulfur provides 1,2,3-thiadiazoles in good yields under metal-free conditions. This procedure serves as an improvement for the Hurd-Mori reaction.
J. Chen, Y. Jiang, J.-T. Yu, J. Cheng, J. Org. Chem., 2016, 81, 271-275.

A highly efficient reaction of readily available tosylhydrazones with ammonium thiocyanate in ecofriendly EtOH as the solvent provides 1,2,3-thiadiazoles in very good yields at room temperature. The reaction shows a wide scope of substrates and good functional-group tolerance.
Y. Lu, Y. Sun, A. Abdukader, C. Liu, Synlett, 2021, 32, 1044-1048.

Visible light along with 1 mol % cercosporin catalyzes the synthesis of 1,2,3-thiadiazoles and 1,4,5,6-tetrahydropyridazines by a photocatalytic process with good regioselectivity and broad functional-group compatibility under mild conditions in a sustainable, environmentally friendly manner.
Y. Zhang, Y. Cao, L. Lu, S. Zhang, W. Bao, S. Huang, Y. Rao, J. Org. Chem., 2019, 84, 7711-7721.

The combination of I2 with dimethyl sulfoxide mediates a cross-coupling cyclization of enaminones, tosylhydrazine, and elemental sulfur for the synthesis of 5-acyl-1,2,3-thiadiazoles in very good yields under transition-metal-free conditions. This strategy is operationally simple and compatible with a wide range of functional groups.
Z. Yang, Y. Liang, A. Li, K. Liu, L. Li, T. Yang, C. Zhou, J. Org. Chem., 2019, 84, 16262-16267.