Yield:77719-02-9 74%

Reaction Conditions:

with sulfonic chloride acid at 20; for 16 h;

Steps:

1.1 Step 1: Preparation of 3-chlorosulfonyl-4-hydroxy-benzoic acid

To a solution of HSO3Cl (31 mL) was added portionwise 4-hydroxybenzoic acid (5.5 g, 39.82 mmol). The mixture was stirred at 20 °C for 16 h. The reaction mixture was dropwise added slowly ice water (300 mL). The mixture was extracted with ethyl acetate (100 mL x 3). The combined organic layers were washed with brine (50 mL), dried over Na₂SO₄, concentrated in vacuo to give a residue. The crude product was triturated with PE (30 mL) at 20^oC for 30 min to afford 3-chlorosulfonyl-4-hydroxy-benzoic acid (4.5 g, 13.72 mmol, 74% yield) as a white solid.¹HNMR (400 MHz, DMSO-d6) δ = 8.09 - 8.06 (m, 1H), 7.82 - 7.75 (m, 1H), 6.89 - 6.81 (m, 1H) ppm.

References:

WO2022/103899,2022,A1 Location in patent:Paragraph 181-182