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With chromium(VI) oxide; sulfuric acid; acetic acid; In water; at 95℃; for 2h;Inert atmosphere;
Concentrated sulfuric acid (195 ml_) was added carefully with stirring to a solution of <strong>[437-86-5]2-fluoro-3-nitrotoluene</strong> (100 g, 645 mmol) in acetic acid (1000 ml_). The mixture was warmed up to 95 C and a solution of chromium trioxide (226 g, 2.25 mol) in water (200 ml) was added dropwise with stirring over 2h. After addition the mixture was heated with stirring for another 3h, allowed to cool down to room temperature and poured into water (3 L). The mixture was extracted with ethyl acetate (3 x 1 L), the combined organic layers were dried over Na2SO4 and concentrated under reduced pressure to afford a light green solid, which was washed with dichloromethane (3 x 300 ml_) and dried under vacuum to afford the title compound as a light yellow solid in the amount of 75 g (62.8% yield). 1 H NMR(300MHz, DMSO) delta ppm 8.27 (m, 1 H), 8.15 (m, 1 H), 7.48 (m, 1 H).
62.8%
With chromium(VI) oxide; sulfuric acid; acetic acid; In water; at 95℃;
Alternative Method of Preparing methyl 3-amino-2-fluorobenzoate (Step B of Intermediate 15 Above); Step A: 2-fluoro-3-nitrobenzoic acid; Concentrated sulfuric acid (195 ml) was added carefully with stirring to a solution of <strong>[437-86-5]2-fluoro-3-nitrotoluene</strong> (100 g, 645 mmol) in acetic acid (1000 ml). The mixture was warmed up to 95 C. and the solution of chromium trioxide (226 g, 2.25 mol) in water (200 ml) was added dropwise with stirring over 2 h. After addition the mixture was heated with stirring for another 3 h, allowed to cool down to room temperature and poured into water (3 L). The mixture was extracted with ethyl acetate (3×1 L), the combined organic layers were dried over Na2SO4 and concentrated under reduced pressure to afford a light green solid, which was washed with dichloromethane (3×300 ml) and dried under vacuum to afford the title compound was obtained as a light yellow solid (75 g, 62.8%). 1H NMR (300 MHz, DMSO) delta ppm 8.27 (m, 1H), 8.15 (m, 1H), 7.48 (m, 1H).
With sodium chlorite; aminosulfonic acid; water; In 1,4-dioxane; at 20℃; for 0.5h;
In a round bottom flask, <strong>[96516-29-9]2-fluoro-3-nitro-benzaldehyde</strong> (15, 1 .02 g, 6.03 mmol) is combined with sodium chlorite ( 1.26 g, 1 1.15 mmol), 60 mL of 1 ,4-dioxane, 20 mL of water, and sulfamic acid (4.47 g, 46.0 mmol) and the reaction is stirred at room temperature for 30 minutes. The mixture is poured into water and extracted with ethyl acetate. The organic layer is washed with water, then brine, dried over magnesium sulfate, filtered and the filtrate is concentrated under vacuum. The resulting material is purified on column chromatography, eluting with methanol and dichloromethane. Appropriate fractions are combined and concentrated under vacuum, then suspended in dichloromethane. The resulting solid is collected by filtration to provide the desired compound (16, 151 mg). MS (ESI) [M-H+]' = 184.4.
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