Synthesis of 1,2,4-oxadiazoles utilizing ethyl 2-cyano-2-(2-nitrophenylsulfonyloxyimino) acetate (ortho-nosylOXY) as a catalyst and dehydrating reagent under microwave irradiation

Abstract

The present work describes the development of an optimized microwave-assisted synthesis of 1,2,4-oxadiazoles from carboxylic acids and amidoximes using ethyl 2-cyano-2-(2-nitrophenylsulfonyloxyimino) acetate (ortho-NosylOXY) as an activating agent of carboxylic acid for O-acylation step followed by cyclization step in one pot with significantly good yield. Interestingly, the same reagent, ortho-NosylOXY, acts as a catalyst for the first step and helps as a dehydrating agent for the second step. Moreover, by-products, Oxyma [ethyl 2-cyano-2-(hydroxyimino) acetate] and 2-nitrobenzenesulfonic acid can easily be recovered back and recycled further to prepare the reagent. This method is environment friendly and cost-effective.