1,3,4-Thiadiazole

Description

1,3,4-Thiadiazole is a five-membered, aromatic, weakly basic, planer, electron-deficient, conjugated heterocyclic ring system comprised of two carbon atoms, one sulfur atom, and two pyridine-like nitrogen atoms present at the 3- and 4-positions of the ring. The dipole moment (3.25 D) for 1,3,4-thiadiazole suggests that it is a polar symmetric molecule with pseudo-aromatic character. The carbon atoms at the 2- and 5-positions are electron deficient because of the inductive effect of nitrogen and sulfur and thus they are inert toward electrophilic substitution but reactive toward nucleophilic attack.

The Uses of 1,3,4-Thiadiazole

1,3,4-Thiadiazole, a bioisostere of the thiazole ring, has been used in the synthesis of cephalosporine and cefazedone, which are used as antibiotics. Megazole is another 1,3,4-thiadiazole-based drug, widely used in the treatment of African trypanosomes, also known as sleeping sickness. Azetepa, a phosphoruscontaining drug, has been used for the treatment of cancer. Tebtheuron is known as a broad-spectrum herbicide and is used to control a variety of weeds and herbaceous and woody plants. Numerous thiadiazole derivatives are patented as bactericides, insecticides, and fungicides.

Definition

ChEBI: 1,3,4-thiadiazole is a thiadiazole.

Chemical Reactivity

Atomic charges have been calculated by the DFT method. The maximum charge was found at the S atom (0.818) and thus it is the favorite position for soft nucleophilic attack. The atomic charge on each carbon is ?0.3275. Because of the presence of the two pyridine-like nitrogen atoms in the ring, which make the C2 - and C5 -positions electronically poor, nucleophilic substitution of the leaving groups present at either the C2 - or C5 -position becomes highly facile. However, the atomic charge on N3 and N4 (?0.0308) makes them preferential sites for electrophilic attack and readily N-alkylated or N-acylated. In strongly basic conditions the thiadiazole ring leads to ring fission.

Biological Activity

Anti-inflammatory,antivira and antimicrobial.