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Example 1 Preparation of 4-ethoxy-1,1,1-trifluoro-3-buten-2-one Ethyl vinyl ether (60 g) and triethylamine (28 g) were placed in an autoclave. The reaction vessel was cooled to 10°C to 15°C with continuous stirring. Trifluoroacetyl fluoride (99 g) was added in batches through an impregnation line of stainless steel cylinders at a temperature of 30°C to 40°C and a pressure of 5 to 10 kg/cm2 . After the addition was completed, the reaction mixture was continued to be stirred for 30 min until the reactor pressure was reduced to 0.25 to 0.5 kg/cm2. Excess trifluoroacetyl fluoride was removed by distillation under reduced pressure, followed by washing the reaction mixture with water. The organic layer was separated and concentrated by decompression to give the title product 4-ethoxy-1,1,1-trifluoro-3-buten-2-one. Yield: 86.2%; purity: 98.2%.