A carbamoyl-substituted nitrileoxide was generated upon treatment of easily available 2-methyl-4-nitro-3-isoxazolin-5(2H)-one with THF (not dried); the reaction proceeded efficiently even in the absence of any special reagents and reaction conditions. The nitrileoxide caused 1,3-dipolarcycloaddition with common aliphatic nitriles or electron-rich aromatic nitriles to afford 3-functionalized 1,2