General procedure for the synthesis of 2-iodo-4-methylphenol from o-amino-p-toluol: Water (10 mL) and concentrated hydrochloric acid (12 M, 2 mL) were added to a 50 mL round-bottom flask, followed by 2-amino-4-methylphenol (615 mg, 5.0 mmol). The mixture was stirred and cooled to 5°C using an external ice bath. A solution of sodium nitrite (NaNO2, 355 mg, 5.15 mmol) in water (2 mL) was slowly added dropwise with vigorous stirring, and stirring was continued for 30 minutes after completion of the drop. The solution turned brown, indicating the formation of diazonium salt. Subsequently, a solution of potassium iodide (KI, 885 mg, 5.35 mmol) in water (2 mL) was added and the reaction mixture formed a dark brown emulsion and stirring was continued for 45 minutes. The mixture was slowly heated to 40 °C, at which point gas escape was observed; the mixture was then refluxed for 1 h, after which it was rapidly transferred to an ice bath at 0 °C for cooling. Excess iodine was quenched by the addition of sodium bisulfite solution and extracted with ether (Et2O, 3 × 10 mL). The organic layers were combined, dried with anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure to remove the solvent. The crude product was purified by column chromatography (eluent: hexane) to afford the target product 2-iodo-4-methylphenol (28f) as a red oil in the yield of 947 mg (81% yield) with a boiling point of 76-78 °C. The product was extracted by IR, 1H NDT, 1H NDT and 1H NDT. The product was characterized by IR, 1H NMR, 13C NMR and GC-MS to confirm the structure.
