Green (sustainable) chemistry provides a framework for chemists, pharmacists, medicinal chemists and chemical engineers to design processes, protocols and synthetic methodologies to make their contribution to the broad spectrum of global sustainability. Green synthetic conditions, especially catalysis, are the pillar of green chemistry. Green chemistry principles help synthetic chemists overcome the problems of conventional synthesis, such as slow reaction rates, unhealthy solvents and catalysts and the long duration of reaction completion time, and envision solutions by developing environmentally benign catalysts, green solvents, use of microwave and ultrasonic radiations, solvent-free, grinding and chemo-mechanical approaches. 1,2,4-thiadiazole is a privileged structural motif that belongs to the class of nitrogen–sulfur-containing heterocycles with diverse medicinal and pharmaceutical applications. This comprehensive review systemizes types of green solvents, green catalysts, ideal green organic synthesis characteristics and the green synthetic approaches, such as microwave irradiation, ultrasound, ionic liquids, solvent-free, metal-free conditions, green solvents and heterogeneous catalysis to construct different 1,2,4-thiadiazoles scaffolds.

The 1,2,3-thiadiazole moiety occupies a significant and prominent position among privileged heterocyclic templates in the field of medicine, pharmacology and pharmaceutics due to its broad spectrum of biological activities. The 1,2,3-thiadiazole hybrid structures showed myriad biomedical activities such as antifungal, antiviral, insecticidal, antiamoebic, anticancer and plant activators, etc. In the present review, various synthetic transformations and approaches are highlighted to furnish 1,2,3-thiadiazole scaffolds along with different pharmaceutical and pharmacological activities by virtue of the presence of the 1,2,3-thiadiazole framework on the basis of structure–activity relationship (SAR). The discussion in this review article will attract the attention of synthetic and medicinal researchers to explore 1,2,3-thiadiazole structural motifs for future therapeutic agents.

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