1,2-Dibromo-1,1,2,2-tetrachloroethane → 3-Bromo-1-(dimethylsulfamoyl)pyrazole

Participants

Reaction Steps

To a solution of N-dimethylsulfamoylpyrazole (44.0 g, 0.251 mol) in dry tetrahydrofuran (500 mL) at −78° C. was added dropwise a solution of n-butyllithium (2.5 M in hexane, 105.5 mL, 0.264 mol) while maintaining the temperature below −60° C. A thick solid formed during the addition. Upon completion of the addition the reaction mixture was maintained for an additional 15 minutes. Then a solution of 1,2-dibromotetrachloroethane (90 g, 0.276 mol) in tetrahydrofuran (150 mL) was added dropwise while maintaining the temperature below −70° C. The reaction mixture turned to a clear orange color. After stirring for an additional 15 minutes, the −78° C. bath was removed and the reaction was quenched with water (600 mL). The reaction mixture was extracted with dichloromethane (4×), and the organic extracts were dried over magnesium sulfate and concentrated. The crude product was further purified by chromatography on silica gel using dichloromethane/hexane (50:50) as eluent to afford the title product as a clear colorless oil (57.04 g). 1H NMR (CDCl3) δ 3.07 (d, 6H), 6.44 (m, 1H), 7.62 (m, 1H.

Provenance & Evidence