General procedure for the synthesis of 5-chloro-2-thiophene carbonyl chloride from 2-acetyl-5-chlorothiophene: To a mixed solution containing 2-acetyl-5-chlorothiophene (0.161 mg, 1.0 mmol), pyridine (0.012 mL, 0.15 mmol), and chlorobenzene (0.35 mL), at room temperature, disulfur dichloride (S2Cl2, 0.16 mL 2.0 mmol) with continuous stirring. After 2 hours of reaction, sulfuryl chloride (SO2Cl2, 0.121 mL, 1.5 mmol) was added dropwise and stirring was continued for 0.5 hours at room temperature. Subsequently, the reaction mixture was heated to 132 °C and stirred at this temperature for 15 hours. Upon completion of the reaction, the reaction mixture was diluted with deuterated chloroform (CDCl3, 2 mL) and an internal standard (tributyl phosphate, 1BU3PO4, 0.0552 mL, 0.20 mmol) was added for nuclear magnetic resonance (1H NMR) analysis.1H NMR analysis showed an 80% yield of 5-chloro-2-thiophene carbonyl chloride.1H NMR (PhCl. CDCl3, 400 MHz) chemical shift values: δ = 7.99 (d, J = 4 Hz, 1H), 6.86 (d, J = 4 Hz, 1H).
