A new and efficient method for the synthesis of 2-N-(aryl)-1,3,4-oxadiazole-2,5-diamine derivatives

Abstract

We report a series of cyclic analogues of 2,5-diamino-1,3,4-oxadiazoles which were prepared in a simple and general protocol. This method involves easy cyclisation of N-(aryl)-1,2-hydrazinedicarboxamides and mediated by tosylchloride/ pyridine in ethanol (solvent) under a reflux condition (79-80°C), over a time period of 20 h. We prepared different examples in a higher range of yields (80-98 %) by using this protocol.

Novel Hydroxamic Acids Containing Aryl-Substituted 1,2,4- or 1,3,4-Oxadiazole Backbones and an Investigation of Their Antibiotic Potentiation Activity

“…The synthesis began with commercially available benzoic acids, 20b , d , e – h , which were converted into esters in the case of compounds 20b , d , e , and in the case of compounds 20f – h , the hydroxyl groups were at the same time methylated to form compounds 27a – f in good yields. Further, a series of hydrazides, 28a – f , without isolation or purification were obtained from esters 27a – f , after which, compounds 28a – f were converted into 1,3,4-oxadiazoles 29a – f , according to a modified known procedure [ 40 ]. The target hydroxamic acids, 30a – f , were obtained in good yields via the reaction of excess hydroxylamine hydrochloride with esters 29a – f in the presence of DIPEA ( Figure 8 ).…”