[OH:1][C:2]1[CH:3]=[CH:4][C:5]([N+:11]([O-:13])=[O:12])=[C:6]([CH:10]=1)[C:7]([OH:9])=[O:8].S(Cl)(Cl)=O.[CH3:18]O>>[OH:1][C:2]1[CH:3]=[CH:4][C:5]([N+:11]([O-:13])=[O:12])=[C:6]([CH:10]=1)[C:7]([O:9][CH3:18])=[O:8]To MeOH (125 mL) was added 5-hydroxy-2-nitrobenzoic acid (1.02 g, 5.6 mmol) followed by dropwise addition of thionyl chloride (˜4 mL) and the mixture heated at reflux overnight. The solution was cooled to room temperature, concentrated in vacuo, reconcentrated twice from MeOH, dissolved in EtOAc, washed with H2O and brine, dried over MgSO4, filtered, and concentrated in vacuo to give methyl 5-hydroxy-2-nitrobenzoate (1.09 g, 5.5 mmol, 98%). 1H NMR (300 MHz, DMSO-d6) δ 11.38 (s, 1H), 8.05 (d, 1H), 7.03 (d, 1H), 7.01 (s, 1H), 3.82 (s, 3H); LC-MS (ESI) m/z 196 (M−H)+.
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