1,3-Dipolar cycloaddition reactions of 1,3,4-oxadiazin-6-ones with nitrile oxides

2,5-Diaryl-1,3,4-oxadiazin-6-ones 1 gave with nitrile oxides 2 1,2,4-oxadiazole derivatives 4 . When mesitonitrile oxide 2a was used, bis-adducts 3 were also formed. The cycloadditions showed a remarkable site selectivity towards one carbon nitrogen double bond. The structure of both adducts was fully characterized by X-ray analysis.