2, 4-Dimethyl-3-phenylisoxazole anhydrobases were easily prepared from the corresponding 5-chloroisoxazolium trifluoromethanesulfonate and carbon anions of 1, 3- dioxo compounds in the presence of triethylamine. Photorearrangement of 2-(2, 4-dimethyl- 3-phenyl-2H-isoxazol-5-ylidene) malonic acid diethyl ester gave a 4, 5- dihydrofuroazetidinone in good yield.