General procedure for the synthesis of ethyl 3-oxo-3-(3-thienyl)propionate from 3-acetylthiophene: First, diethyl carbonate (36.3 mL, 300 mmol) was dissolved in toluene (18 mL) and the solution was heated to 60 °C. At this temperature, potassium tert-butoxide (13.0 g, 120 mmol) was added in batches, and after the addition, the reaction mixture was continued to be heated at 65°C for half an hour. Subsequently, the temperature was raised to 75 °C and a solution of 3-methylthiophene (9.2 g, 73 mmol) in toluene (18 mL) was slowly added dropwise. After the dropwise addition, the reaction mixture was heated at 80 °C for 90 min. After completion of the reaction, it was cooled to room temperature, the precipitated solid was collected by filtration and washed thoroughly with ether. The resulting solid was dissolved in water and extracted successively with ethyl acetate. The organic phases were combined, washed with brine, dried over anhydrous sodium sulfate, filtered and the solvent was evaporated to give the dark oily product ethyl 3-oxo-3-(3-thienyl)propionate (12.0 g, 83% yield). The NMR hydrogen spectrum (CDCl3) data of the product were as follows: δ 1.25 (t, 3H), 3.90 (s, 2H), 4.20 (q, 2H), 7.35 (m, 1H), 7.55 (m, 1H), 8.10 (m, 1H).
