2-Iodobutane → 1-sec-butyl-4-iodo-5-(2-thienyl)-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

To a solution of 4-iodo-3-(2-thienyl)-1H-pyrazole (7.1 mmol) in 57 mL dry N,N-dimethylformamide under argon atmosphere at 0° C. was added sodium hydride (8.5 mmol, 60% dispersion in mineral oil) in portions. The reaction mixture was stirred at 0° C. for 15 min, then 2-iodobutane (10.6 mmol) was added dropwise. After 14 h at room temperature, 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 2.7 g of a mixture of 1-sec-butyl-4-iodo-3-(2-thienyl)-1H-pyrazole and 1-sec-butyl-4-iodo-5-(2-thienyl)-1H-pyrazole (80:20; 88% yield). The mixture was purified by chromatography on silica gel (toluene:ethyl acetate 100:0 to 0:100 and cyclohexane:toluene 100:0 to 0:100) to afford 1.16 g 1-sec-butyl-4-iodo-3-(2-thienyl)-1H-pyrazole (48% yield) and 71 mg of 1-sec-butyl-4-iodo-5-(2-thienyl)-1H-pyrazole (3% yield).

Provenance & Evidence