A convenient and efficient synthetic approach for the synthesis of 5-substituted 3-aryl-4,5-dihydroisoxazoles is reported. In the presence of triethylamine, a series of hydroximoyl chlorides were transformed into nitrile oxides, followed by reaction with N-vinyl-2-pyrrolidinone (or 4-vinylpyridine) by a 1,3-dipolar cycloaddition to give novel 4,5-dihydroisoxazole derivatives.