C(O)(=O)C.[CH3:5][C:6]1[C:14]([CH3:15])=[CH:13][CH:12]=[CH:11][C:7]=1[C:8]([OH:10])=[O:9].[N+]([O-])(O)=O.[Br:20]Br>O.[N+]([O-])([O-])=O.[Ag+]>[Br:20][C:12]1[CH:13]=[C:14]([CH3:15])[C:6]([CH3:5])=[C:7]([CH:11]=1)[C:8]([OH:10])=[O:9]
To a stirred acetic acid solution (0.2 M) of 2,3-dimethylbenzoic acid (1 eq.) was added sequentially nitric acid (12 eq.), water (25 eq.) and bromine (1.1 eq.). Finally, silver nitrate (1 M aqueous solution, 1.3 eq.) was added dropwise over a period of 30 min. After another hour of stirring at RT, the crude reaction mixture was diluted with water and extracted with EtOAc. The combined organic extracts were then washed with brine, dried over Na2SO4, filtered and the filtrate concentrated in vacuo. Trituration of the crude product thus obtained in hexanes afforded the title compound as a yellow solid.
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