[Synthesis]
To a solution of N-(2,3-dimethyl-6-nitrophenyl)acetamide (16.0 g, 1.0 eq.) was added a 60% aqueous sulfuric acid solution (150 mL). The reaction mixture was heated to reflux temperature and kept for 1 hour. Upon completion of the reaction, the mixture was cooled to room temperature. Subsequently, it was diluted with ice water (100 mL) and neutralized with 2N sodium hydroxide solution. The reaction mixture was extracted with ethyl acetate (3 x 50 mL). The organic layers were combined and washed sequentially with saturated sodium bicarbonate solution (2 x 50 mL) and saturated sodium chloride solution (2 x 50 mL). The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography (eluent: 10% dichloromethane/hexane) to afford 2,3-dimethyl-6-nitroaniline (5.5 g, 43% yield) and 2,3-dimethyl-4-nitroaniline (1.5 g, 12% yield).
NMR hydrogen spectral data of 2,3-dimethyl-6-nitroaniline (5.5 g, 43%): 1H NMR (CDCl3) δ 2.05 (s, 3H), 2.20 (s, 3H), 6.15 (br s, 2H), 6.45 (d, J = 8.7 Hz, 1H), 7.63 (d, J = 9.0 Hz, 1H); 1H NMR (DMSO -d6) δ 2.10 (s, 3H), 2.30 (s, 3H), 6.50 (d, J = 8.7 Hz, 1H), 7.15 (br s, 2H), 7.75 (d, J = 9.0 Hz, 1H).
NMR hydrogen spectral data of 2,3-dimethyl-4-nitroaniline: 1H NMR (CDCl3) δ 2.10 (s, 3H), 2.45 (s, 3H), 4.05 (br s, 2H), 6.45 (d, J = 9.0 Hz, 1H), 7.65 (d, J = 8.7 Hz, 1H); 1H NMR (DMSO-d6) δ 2.00 ( s, 3H), 2.35 (s, 3H), 6.12 (br s, 2H), 6.53 (d, J = 9.0 Hz, 1H), 7.63 (d, J = 9.0 Hz, 1H). |