Iodoethane → 5-(4-chloro-2-thienyl)-1-ethyl-4-iodo-1H-pyrazole

Participants

Reaction Steps

To a solution of 4-iodo-3-(2-thienyl)-1H-pyrazole (4.8 mmol) in 15 mL dry N,N-dimethylformamide under argon atmosphere was added sodium hydride (5.8 mmol, 60% dispersion in mineral oil) in portions at 0° C. The reaction mixture was allowed to warm to room temperature and was stirred for 15 min. After cooling to 0° C., ethyliodide (7.2 mmol) was added dropwise. The reaction mixture was stirred at room temperature overnight. Sodium hydride (1.2 mmol) and ethyliodide (2.5 mmol) were added and stirring was continued for 24 h. Water and MTBE were added to the reaction mixture. The phases were separated and the aqueous phase was extracted with MTBE. The combined organic extracts were successively washed with water and brine, dried over MgSO4, filtered and concentrated to afford 1.71 g of a mixture of 3-(4-chloro-2-thienyl)-1-ethyl-4-iodo-1H-pyrazole and 5-(4-chloro-2-thienyl)-1-ethyl-4-iodo-1H-pyrazole (80:20; 84% yield). The mixture was purified by chromatography on silica gel (toluene:ethyl acetate 100:0 to 0:100) to afford 1.27 g 3-(4-chloro-2-thienyl)-1-ethyl-4-iodo-1H-pyrazole (78% yield) and 92 mg of 5-(4-chloro-2-thienyl)-1-ethyl-4-iodo-1H-pyrazole (6% yield).

Provenance & Evidence