Question

Thiosemicarbazide phenylacetic acid reaction

Answer 1

A facile and general protocol for the preparation of 2-amino-1, 3, 4-oxadiazoles is reported. This method relies on a tosyl chloride/pyridine-mediated cyclization of a thiosemicarbazide, which is readily prepared by acylation of a given hydrazide with the appropriate isothiocyanate. Cyclization of the thiosemicarbazide consistently outperforms the analogous semicarbazide cyclization under these conditions, for 18 distinct examples. Utilizing this protocol, we have prepared 5-alkyl-and 5-aryl-2-amino-1, 3, 4-oxadiazoles in 78− 99% yield.