ABS (0.5 mmol) was dissolved in 1 ml of N,N′-dimethylformamide (DMF), and triethylamine (3 mmol) was added into the above solution. 1,1′-thiocarbonyldiimidazole (1 mmol) was dissolved in 1.5 ml of DMF at 50°C and added dropwise to the above solution. The solution was continuously stirred at room temperature for 30 min and then quenched by ddH2O. The product was first extracted with ethyl acetate and then purified by silica gel chromatography (ethyl acetate–hexane). 1H NMR [400 MHz, dimethyl sulfoxide (DMSO)-d6]: δ 7.79 (d, J = 7.8 Hz, 2H), 7.49 (d, J = 7.8 Hz, 2H), 7.35 (s, 2H), 3.96 (t, 2H), and 3.04 (t, 2H).