Sulfuric Acid → 2-Bromo-5-fluoro-1-nitro-3-(trifluoromethyl)benzene

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Reaction Steps

2-Bromo-5-fluoro-benzotrifluoride (XVII) (50 g, purchased from ABCR, F01421) is dissolved in 750 mL of dichloromethane. Potassium-nitrate (60.54 g) is added under stirring, followed by slow addition of sulfuric acid (587.3 g, 20% SO3, Riedel de Haen 30736). The temperature of the reaction mixture is kept at 25-30° C. by gentle cooling during the addition of the sulfuric acid. The reaction mixture is stirred for additional 25 hours at room temperature, after which time an IPC indicated >97% conversion. For work-up, the layers are separated and the acid layer is extracted by stirring with dichloromethane (2×300 mL). The dichloromethane phases are combined and washed sequentially with 1,000 mL of saturated aqueous NaHCO3 solution, 1,000 mL of aqueous sulfamic acid solution (5% m/m), 1,000 mL of saturated aqueous NaHCO3 solution and 1,000 mL of water. The dichloromethane solution is dried on anhydrous MgSO4 and the solvent is evaporated under reduced pressure to obtain 2-bromo-5-fluoro-1-nitro-3-trifluoromethyl-benzene (XVIII) as a yellow liquid. GC-MS: m/z: 287, 268, 257, 241, 229. These mass peaks are accompanied by the corresponding isotope peaks characteristic for bromine containing compounds. IR (film): 3101, 1618, 1591, 1554, 1454, 1423, 1365, 1319, 1232, 1186, 1153, 1113, 883 cm−1.

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