[C:1]1([CH3:11])[CH:6]=[CH:5][CH:4]=[CH:3][C:2]=1[CH2:7][C:8]([OH:10])=[O:9].S(=O)(=O)(O)O.[N+:17]([O-])([OH:19])=[O:18]>C(Cl)Cl>[CH3:11][C:1]1[CH:6]=[CH:5][C:4]([N+:17]([O-:19])=[O:18])=[CH:3][C:2]=1[CH2:7][C:8]([OH:10])=[O:9]A solution of 2-o-tolylacetic acid (3.54 g, 23.6 mmol) in DCM (12 mL) was added to a pre-cooled mixture of concentrated sulfuric acid (10 mL, 188 mmol) and 90% nitric acid (1 mL, 22.4 mmol) at −20° C. The reaction mixture was stirred at −20° C. for 30 minutes, then slowly warmed to room temperature and stirred overnight. The reaction mixture was poured into ice-water. The white solid was collected by filtration, rinsed with water, and concentrated. The solid was triturated with ether and filtered to obtain Intermediate 80A (2.4 g, 42%) as a white solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 12.62 (1H, br. s.), 8.13 (1H, d, J=2.51 Hz), 8.04 (1H, dd, J=8.28, 2.51 Hz), 7.47 (1H, d, J=8.53 Hz), 3.80 (2H, s), 2.34 (3H, s).
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