General procedure for the synthesis of 4-iododibenzothiophene from dibenzothiophene: To a stirred, cooled-to-0 °C solution of 2,2,6,6-tetramethylpiperidine (0.25 mL, 1.5 mmol) in tetrahydrofuran (THF, 2-3 mL) was sequentially added a hexane solution (1.5 mmol) of 1.6 M butyl lithium (BuLi) for 5 min followed by ZnCl2- TMEDA (0.13 g, 0.50 mmol). The reaction mixture was continued to be stirred at 0 °C for 15 min, followed by the addition of dibenzothiophene (1a, 0.20 g, 1.0 mmol). After 2 h of reaction at this temperature, a THF (4 mL) solution of iodine (I2, 0.38 g, 1.5 mmol) was added. The mixture was stirred overnight and then saturated aqueous sodium bicarbonate (NaHCO3) and sodium thiosulfate (Na2S2O3, 4 mL) solutions were added sequentially. The mixture was extracted with ethyl acetate (EtOAc, 3 x 20 mL), the organic layers were combined, dried with magnesium sulfate (MgSO4), filtered and concentrated under reduced pressure. Finally, the target product 4-iododibenzothiophene was purified by silica gel column chromatography (eluent: heptane/dichloromethane (CH2Cl2) gradient from 100:0 to 80:20).
