1,3,4-Thiadiazole: Synthesis, reactions, and applications in medicinal, agricultural, and materials chemistry

A glance at standard reference works shows 1,3,4-thiadiazole has been investigated more than other isomers. The 1,3,4-thiadiazole ring is a very weak base due to the inductive effect of the sulfur atom and possesses relatively high aromaticity. In addition, the ring is also shown to be very electron deficient due to the electron-withdrawing effect of the nitrogen atoms and relatively inert toward electrophilic substitution but susceptible to nucleophilic attack, whereas when substitutions are introduced into the 2' or 5' position of this ring, it would be highly activated and readily react to yield diverse derivatives. Thus, possessing these properties, 1,3,4-thiadiazole derivatives are applied widely in pharmaceutical, agricultural, and materials chemistry. In particular, the 1,3,4-thiadiazoles display a broad spectrum of biological activities including antimicrobial, antituberculosis, antioxidant, anti-inflammatory, anticonvulsants, antidepressant and anxiolytic, antihypertensive, anticancer, and antifungal activity.