No abstract

No abstract

Heterocycles closely intertwine chemistry with biology reflecting the presence of nitrogen‐based heterocyclic ring structure in nearly 75 % of small‐molecule drugs. The number of reported strategies for the synthesis of several “privileged scaffolds” has expanded, amongst which, cyclodesulfurization of thioureas offers a quick access to highly substituted heterocycles, thereby playing a role of an excellent tool in organic syntheses of natural products and pharmaceutically active compounds. This comprehensive review emphasizes the applications of cyclodesulfurization as an integral synthetic step in the synthesis of nitrogen, oxygen and sulfur‐containing heterocycles. Furthermore, a survey of cyclodesulfurizing agents reported since 2000 is comprehensively reviewed and summarized.

A one-pot synthesis of 2-amino-1,3,4-oxadiazoles has been achieved from the corresponding isothiocyanates and hydrazides in the presence of tert-butyl hydroperoxide (TBHP) and water under microwave irradiation. The thiosemicarbazides intermediate could be derived in situ which underwent an intramolecular cyclodesulfurization under microwave irradiation. Apart from being simpler and green, this method offers significant advantages, such as short reaction times, economy and no requirement for a catalyst, with easy workup procedures to afford a variety of 2-amino-1,3,4-oxadiazoles in significantly high yields (85-98 %). Spectroscopic techniques were employed to elucidate the chemical structures of the final compounds and ESI-MS technique was employed to establish the formation of thiosemicarbazide intermediate and requirement of oxygen source for the completion of reaction and the most plausible reaction mechanism.

No abstract