3-Bromothiophene → 3-Bromothiophene-2-sulfonyl chloride

Participants

Reaction Steps

Chlorosulfonic acid (20 ml, 300 mmol) was added to a solution of 3-bromothiophene (8.15 g, 50 mmol) in methylene chloride (50 ml) at −78° C. over a 20 min. period. After the completion of addition, the cold bath was removed and stirring continued at ambient temperature for 1 hr. The reaction mixture was carefully added, dropwise, to crushed ice (100 g). The mixture was extracted with methylene chloride (2×100 ml). The combined organic layers was dried over MgSO4 and evaporated. The crude product was purified by flash chromatography on silica gel using hexane as the eluent resulting in 3-bromothiophene-2-sulfonyl chloride (4 g, 30% yield) and 4-bromothiophene-2-sulfonyl chloride (200 mg,≦1%).

Provenance & Evidence