General procedure: preparation of 2-(4-iodo-1H-pyrazol-1-yl)ethanol
4-Iodo-1H-pyrazole (4.50 g, 23.20 mmol) was dissolved in N,N-dimethylformamide (DMF, 45 mL), and sodium hydride (60% w/w, 1.42 g, 35.5 mmol) was added at 0 °C and stirred at room temperature for 1 hour. Subsequently, 2-bromoethanol (2.5 mL, 35.2 mmol) was added dropwise to the reaction mixture at 0 °C. The reaction system was warmed up to 65 °C and stirred continuously for 3 days. Upon completion of the reaction, the reaction was quenched with saturated sodium chloride solution and ethyl acetate (EtOAc) and the aqueous phase was extracted with ethyl acetate. The organic phases were combined, washed sequentially with water and saturated sodium chloride solution, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography using cyclohexane/ethyl acetate (0 to 50% gradient) as eluent to afford the target compound 2-(4-iodo-1H-pyrazol-1-yl)ethanol (3.55 g, 64% yield).
1H NMR (500 MHz, CDCl3): δ 7.55 (s, 1H), 7.52 (s, 1H), 4.32-4.22 (m, 2H), 4.04-3.95 (m, 2H), 2.79-2.68 (br m, 1H).
LCMS (ESI) Rt = 1.50 min, MS m/z 238 [M + H]+.
