Benzoic acid, 2-fluoro-5-sulfino- synthesis

Yield:1229627-84-2 72%

Reaction Conditions:

Stage #1: 2-fluoro-5-chlorosulfonylbenzoic acidwith sodium hydroxide;sodium sulfite in water at 20; for 0.75 h;
Stage #2: with sulfuric acid;water pH=2;

Steps:

B.21.a

EXAMPLE B21 Rac-5-Ethanesulfonyl-2-(2,2,2-trifluoro-1-methyl-ethoxy)-benzoic acid (a) 2-Fluoro-5-sulfino-benzoic acid; 264 mmol 5-Chlorosulfonyl-2-fluoro-benzoic acid (CAS: 37098-75-2) was added portionwise onto a solution of 1.98 mol sodium sulfite in 1 L of water. The reaction mixture was kept under basic conditions by the addition of the proper amount of 20% NaOH and was stirred at room temperature for 45 minutes. After such time the reaction mixture was cooled down with an ice bath and was then acidified by the addition of 20% H₂SO₄ solution until reaching pH 2. Water was evaporated and 600 ml methanol was added. The mixture was stirred overnight and filtrated. The filtrate was evaporated and dried to yield the title compound as a white solid (72%). MS (m/e): 203.0 ([M-H, 100%)

References:

US2006/178381,2006,A1 Location in patent:Page/Page column 71