1,3-Difluoro-2,4-dimethoxy-5-nitrobenzene → 3,5-Difluoro-2,4-dimethoxybenzenamine

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Reaction Steps

The nitro group of 3,5-difluoro-2,4-dimethoxynitrobenzene (10.9 g, 49.7 mmol) is reduced by catalytic hydrogenation at 40 psi in ethanol/ethyl acetate over 10% Pd/carbon. Progress is monitored by TLC. When the reaction is complete, the catalyst is collected on a diatomaceous earth pad over a glass frit via filtration. The filtrate is concentrated in vacuo, giving pure 1-amino-3,5-difluoro2,4-dimethoxybenzene (2) as 9.40 g (99.8%) of a clear, pale brown oil: 1H NMR (CDCl3) 6.25 (dd, 1H), 3.89 (two s, 6H), 3.7 (br s, 2H); 19F NMR (CDCl3) 135.5 (d, 1F), 146.9 (s, 1F). Anal. calc. for C8H9NO2F2 : C, 50.80; H, 4.80; N, 7.40. Found: C, 50.61; H, 4.81; N, 7.26. The hydrochloride salt is obtained by treating a dioxane solution of 5 with 4M HCl in dioxane, collecting the precipitate on a Buchner funnel, rinsing with dioxane, and drying in vacuo to give the hydrochloride salt of Compound 2 as a bone-white powder: m.p. 213°-218° C. (dec.); 1H NMR (D2O) 7.1 (br d, 1H), 4.05 (br s, 6H); 19F (D2O) 131.1 (dd, 1F), 141.6 (s, 1F). Anal. calc. for C8 H10NO2F2Cl: C, 42.59; H, 4.47; N, 6.21. Found: C, 42.75; H, 4.47; N, 6.14.

Provenance & Evidence