Experiencing a synthesis one-pot of 1,2,4-Oxadiazole mediated by microwave oven: Green chemistry in focus

Abstract

1,2,4-oxadiazoles are compounds that have attracted the attention of many researchers due to their wide range of biological activities, for example, anti-inflammatory, antimicrobial, antitumor etc. The syntheses are based mostly on the use of amidoximes and acylating agents as the initial reactants. This work aims to describe a one-pot reaction for the synthesis of 1,2,4-oxadiazols, mediated by microwave irradiation, employing home-use microwave oven, in the discipline of heterocyclic Chemistry in the postgraduate. The methodology consisted of the reaction of nitriles, hydroxylamine hydrochloride, potassium carbonate and different esters to obtain 1,2,4-oxadiazole. The reactions include two sequential procedures: base-promoted intermolecular addition of hydroxylamine to nitrile to lead to amidoxime, then treatment of the amidoxime with esther to form 1,2,4-oxadiazoles in good yields. This method represents a direct and simple protocol for the synthesis of 3,5- disubstituted 1,2,4-oxadiazoles. It was initially discussed with the students the chemistry of the oxadiazoles, one-pot reactions and green chemistry through atheoretical-expository-dialogue strategy. In the course of the didactic intervention the students, through a thematic seminary, presented the results of the analysis of the spectra from the different techniques used. With the skills acquired from completing this laboratory work, the students become well-prepared to perform spectroscopic analyzes in subsequent experiments encountered in the organic chemistry laboratory.