2-Bromothiophene → 5-Bromothiophene-2-sulfonyl chloride

Participants

Reaction Steps

Chlorosulfonic acid was added dropwise over 20 min. to a cold solution (-78° C.) of 2-bromothiophene (16.3 g, 100 mmol) in methylene chloride (50 ml). After addition of chlorosulfonic acid complete, the cold bath was removed. The reaction mixture was allowed to attain room temperature slowly (2 h), was added dropwise onto the crushed ice (1000 g) and was extracted with methylene chloride (4×100 ml). The combined organic layers was dried over MgSO4, filtered and the solvent was removed under reduced pressure to give a crude product. This was purified by column chromatography using hexane as eluent to give 5-bromothiophene-2-sulfonyl chloride (22 g, 75% yield).

Provenance & Evidence