Preparation of B: 4-fluoro-1,2-dimethylbenzene A (50.0 g, 402.7 mmol) was dissolved in 150 mL of water/tert-butanol (70/30, v/v) mixed solvent with an excess of KMnO4 (400 g, 2.54 mol). After the reaction mixture was refluxed overnight, EtOH (900 mL) was added to quench the unreacted KMnO4, followed by distillation to remove the alcohol. The resulting brown suspension was filtered through a diatomaceous earth pad and the filtrate was concentrated and acidified with concentrated HCl. The product was collected by filtration, the aqueous phase was extracted with EtOAc and the organic phase was dried with Na2SO4. After evaporation of the solvent under reduced pressure, a white solid B (70.0 g, 94% yield) was obtained.1H-NMR (400 MHz, DMSO-d6): δ 7.39 (m, 1H), 7.63 (br s, 1H), 7.99 (br s, 1H).
