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

참여 물질

반응 단계

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, after which time 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 a clear orange; stirring was continued 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 methylene chloride (4×), and the organic extracts were dried over magnesium sulfate and concentrated. The crude product was further purified by chromatography on silica gel using methylene chloride-hexane (50:50) as eluent to afford the title product as a clear colorless oil (57.04 g).

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