4H-3,1-Benzoxazin-4-ones Instead of Isatoic Anhydride: Reducing the Activity of the Substrate Allows You to Reduce the Synthesis Time

Abstract

A method was developed for one-step preparing 5-(2-acylaminophenyl)-3-aryloxadiazoles by the reaction of amidoximes with benzoxazines, which does not require elevated temperatures and a long reaction time. Using a strong basic medium—a solution of NaOH in DMSO—allows for rapid condensation of the intermediately formed O-acylamidoximes at room temperature. Compared with a similar method for the synthesis of unsubstituted 5-(2-aminophenyl)oxadiazoles based on the isatoic anhydride reaction, the proposed one-step procedure not only makes it possible to obtain acyl derivatives of these amino heterocycles, but also reduces the reaction time 20-fold.