1. Acetamidoacetophenone (0.2 g, 1.13 mmol) was dissolved in acetone (2 mL), potassium hydroxide (63 mg, 1.13 mmol) was added, followed by ethyl iodide (0.45 mL, 5.64 mmol). After stirring at room temperature overnight, the reaction mixture was concentrated to dryness. The residue was redissolved in ethyl acetate, washed sequentially with water and brine and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to give N-(3-acetylphenyl)-N-ethylacetamide as an orange powder (0.23 g, 100%) with a melting point of 203-204 °C.
2. The above product (0.23 g, 1.13 mmol) was dissolved in acetonitrile (2 mL), N,N-dimethylformamide dimethyl acetal (150 μL, 0.12 mmol) was added, and the reaction was carried out in a microwave reactor at 180 °C for 10 min. After evaporation of the solvent, the residue was filtered and washed with ethyl acetate/petroleum ether (1:3) to afford N-[3-(3-dimethylaminopropenoyl)phenyl]-N-ethylacetamide as an orange solid (0.30 g, 100%).
3. The above substance (0.228 g, 0.88 mmol), 4-hydroxyphenylguanidine nitrate (0.188 g, 0.88 mmol) and sodium hydroxide (35 mg, 0.88 mmol) were mixed in acetonitrile (2 mL), and heated in a microwave reactor for 15 min at 190 °C. After evaporation of the solvent, the residue was purified by silica gel column chromatography (ethyl acetate/petroleum ether, 1:1) to afford N-ethyl-N-3-[(3-dimethylamino-1-oxo-2-propenyl)phenyl]-acetamide as a yellow solid (117 mg, 38%).
