[CH3:1][O:2][C:3]1[C:4]([CH3:15])=[C:5]([C:9]([N+:12]([O-:14])=[O:13])=[CH:10][CH:11]=1)[C:6]([OH:8])=[O:7].[C:16]([O-])([O-])=O.[Cs+].[Cs+].IC.O>CO>[CH3:16][O:7][C:6](=[O:8])[C:5]1[C:9]([N+:12]([O-:14])=[O:13])=[CH:10][CH:11]=[C:3]([O:2][CH3:1])[C:4]=1[CH3:15]To a solution of 3-Methoxy-2-methyl-6-nitro-benzoic acid in 45 mL of methanol, Cs2CO3 (7.8 g, 24 mmol) is added and stirred at the room temperature for 1 hour. The solution is concentrated under reduced pressure then the resulting yellow solid is suspended in 45 ml of DMF. Iodomethane (1.5 ml 24 mol) is added at 0° C. and stirred at the room temperature for 21 hours. Water is added to the solution and the precipitates are collected and washed by water to give 3-Methoxy-2-methyl-6-nitro-benzoic acid methyl ester (4.0 g) as orange solid in 81% yields. 1H-NMR (400 MHz, δ, ppm) CDCl3: 2.2 (s, 3H), 3.93 (s, 3H), 3.98 (s, 3H), 6.91 (d, 1H), 8.11 (d, 1H).
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