General procedure for the synthesis of ethyl 3-phenylisoxazole-5-carboxylate from (E)-N-hydroxybenzimidoyl chloride and ethyl propargylate: preparation of the intermediate 54-ethyl S-phenylisoxazole-δ-carboxylic acid ethyl ester. The reaction was carried out by stirring ethyl propiolate (0.657 mL, 6.43 mmol), (E)-N-hydroxybenzenecarboximidoyl chloride (0.500 g, 3.21 mmol), and sodium bicarbonate (0.818 g, 9.64 mmol) in a mixed solvent of ethyl acetate (16 mL) and water (1 mL) at room temperature overnight. After completion of the reaction, the reaction mixture was filtered and the filtrate was concentrated under reduced pressure. The crude product was purified by fast column chromatography on silica gel, the eluent being a heptane solution of 5% to 80% dichloromethane, to give 0.295 g of ethyl 3-phenylisoxazole-5-carboxylate in 42% yield.ESI/APCI (+): 218 (M + H).
