Chlorosulfonic acid → 5-Chloro-4-(2,5-difluorophenyl)thiophene-2-sulfonyl chloride

Participants

Reaction Steps

To a solution of 2-chloro-3-(2,5-difluorophenyl)thiophene (0.73 g, 3.2 mmol) in CH2Cl2 (100 mL), cooled on ice, chlorosulfonic acid (0.37 g, 3.2 mmol) in CH2Cl2 (50 mL) was added dropwise over 1 h. The reaction was refluxed over night. The reaction mixture was cooled and washed with water (2×100 mL) and brine, dried over MgSO4, filtered and concentrated to a dark brown oil. The oil was dissolved in heptane (50 mL) and stored in the fridge over the weekend. A black tar precipitated. The solution was decanted and concentrated to give the title compound as a light brown oil (0.87 g, 21% over two steps). MS (ESI+) m/z 293 [M−Cl]+.

Provenance & Evidence