The Reaction of 1,3,5-Triazine with Aromatic Nitrile Oxides. A New Synthesis of 3-Substituted 1,2,4-Oxadiazoles

Abstract

Abstract The cycloaddition of aromatic nitrile oxides(2a=benzo-; 2b=p-tolu-; 2c=mesitylenecarbo-) with 1,3,5-triazine(1) is reported. The corresponding 3-substituted 1,2,4-oxadiazoles(3a,b,c) are obtained in fair yields only when BF3 is added. It was stoichiometrically confirmed that one mol of 1 behaves so as to supply three mols of azomethine radicals. A reaction scheme initiated from a two-step cycloaddition of 2 to 1 activated by BF3 is suggested. The mixture, 1 : 2c : BF3=1 : 3 : 1, afforded a better yield of 3c(69%) than an equimolar mixture of 2c with ethyl formimidate or formamidine.