Hydrochloric Acid → Methyl 4-(chlorosulfonyl)-2-fluorobenzoate

Participants

Reaction Steps

To a suspension of methyl 4-amino-2-fluorobenzoate hydrochloride (Preparation 12, 33.2 g, 0.154 mmol, 1 eq) in a 1:1 mixture of concentrated HCl and water (70 ml:70 ml) cooling in an ice bath was added a solution of sodium nitrite (11.71 g, 0.169 mol, 1.1 eq) in warm water (20 ml) dropwise maintaining the temperature below 50° C. The reaction mixture was allowed to stir for 10 minutes then filtered through a pad of Celite and the solid washed with water. The filtrate was added portionwise to a solution of sulphur dioxide (49.4 g, 0.771 mmol, 5 eq) and copper (1) chloride (100 mg) in AcOH (120 ml) at 0° C. and the reaction mixture stirred for 30 minutes. The mixture was extracted with DCM (3×150 ml), washed with saturated sodium hydrogen carbonate, water and brine, dried over magnesium sulphate, filtered and evaporated in vacuo. The crude material was purified by column chromatography eluting with 10% ethyl acetate:hexane to yield the title compound as a red oil (19.68 g, 0.078 mol, 50%).

Provenance & Evidence