Hydrochloric Acid → 7-Chloronaphthalene-2-sulfonic acid

Participants

Reaction Steps

A solution of sodium 7-aminonaphthalene-2-sulfonate (Pfaltz and Bauer, 1.00 g, 4.08 mmol) in water (6.0 mL) and conc. HCl (6.0 mL) was cooled to 0° C. A premixed solution of NaNO2 (295 mg, 4.28 mmol) in water (3.0 mL) was added slowly, maintaining the temperature close to 0° C. The resulting reaction mixture was stirred at room temperature for 30 min. A solution of CuCl (807 mg, 8.16 mmol) in water (1.0 mL) and conc. HCl (4.0 mL) was then added dropwise over 30 min, maintaining the temperature close to 0° C. The reaction mixture was stirred at room temperature for 2 h, then concentrated in vacuo and dissolved in a small amount of water. The solids were filtered off and retained. The filtrate was concentrated in vacuo, purified by preparative HPLC and combined with the filtered solids to give the title compound (843 mg, 85%) as a dark grey solid. MS(ESI−) m/z 241.2 (M−H)−.

Provenance & Evidence