General procedure for the synthesis of 6-iodobenzo[d]thiazole from 6-aminobenzothiazole: A mixture of concentrated sulfuric acid (45 mL) and sodium nitrite (NaNO2, 3.04 g, 44 mmol) was heated to 70 °C and maintained for 15 min, and then cooled to 40 °C. At this temperature, a solution of 6-aminobenzothiazole (1a, 6.0 g, 40 mmol) or 6-amino-2-methylbenzothiazole (1b, 6.57 g, 40 mmol) in acetic acid (80 mL) was added, and the reaction was stirred at room temperature for 30 min. A solution of potassium iodide (KI, 7.32 g, 44 mmol) in water (70 mL) was heated to 70 °C and the pre-prepared diazonium salt solution was added slowly. After 30 min of reaction, the mixture was poured into ice water, the crude product was collected by filtration, washed with water and subsequently dissolved in dichloromethane. The dichloromethane layer was treated with 10% sodium thiosulfate (Na2S2O3) solution, washed with water and dried sequentially. After concentration to remove the solvent, the residue was purified by silica gel column chromatography (eluent: dichloromethane) to give the target product.
![6-iodobenzo[d]thiazole](/CAS/GIF/654070-00-5.gif)