CYCLOADDITIONS OF NITRILE OXIDES TO AMIDOXIMES - A GENERAL-SYNTHESIS OF 3,5-DISUBSTITUTED 1,2,4-OXADIAZOLE-4-OXIDES

The cycloaddition of nitrile oxides to amidoximes is a general method for the sinthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides with the same or different substituents. The yields are only moderate since an equivalent amount of the nitrile oxide is consumed by reaction wit h the amine released in the fragmentation of the primary cycloadducts and reforms the amidoxime. With excess nitrile oxides the 1,2,4-oxadia zole-4-oxides undergo a disproportionation reaction to yield nitroso-c arbonyl intermediates and 1,2,4-oxadiazoles. (C) 1997, Elsevier Scienc e Ltd.