Water → 4-Bromo-3-fluorobenzoic acid

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Reaction Steps

4-Bromo-3-fluorotoluene (40.0 g, 0.212 mol) was heated at 90° C. in H2O (200 mL)-pyridine (200 mL) with mechanical stirring under Ar. Potassium permanganate (KMnO4) (67 g, 0.424 mol) was added portionwise over 3 h. After 4 h, an HPLC of a filtered sample indicated 50% conversion to the acid. An additional 30 g of KMnO4 was added and heating continued overnight. HPLC indicated 81% conversion. Further KMnO4 was added portionwise with reaction monitoring by HPLC until >95% conversion was obtained. The reaction mixture was filtered through Celite, the filter pad washed with H2O, aq NaOH and EtOH. The filtrate was concentrated to a small volume, then partitioned between 3N NaOH solution and diethyl ether. The aqueous basic layer was separated, cooled in an ice-H2O bath and acidified slowly with 6N HCl solution to precipitate the white solid product. This was collected by suction filtration and dried at 40° C. in a vacuum oven overnight to give the title compound. mp 190-192° C. 1H NMR (CDCl3) δ 7.83 (dd, 1H, J=2, 9 Hz), 7.78 (dd, 1H, J=2, 8 Hz), 7.67-7.71 (m, 1H).

Provenance & Evidence