[CH3:1][O:2][C:3](=[O:26])[C:4]1[CH:9]=[C:8]([C:10]#[C:11][Si](C)(C)C)[C:7]([F:16])=[C:6]([F:17])[C:5]=1[NH:18][C:19]1[CH:24]=[CH:23][CH:22]=[CH:21][C:20]=1[Cl:25].[OH:27]S(O)(=O)=O>CC(C)=O.O>[CH3:1][O:2][C:3](=[O:26])[C:4]1[CH:9]=[C:8]([C:10](=[O:27])[CH3:11])[C:7]([F:16])=[C:6]([F:17])[C:5]=1[NH:18][C:19]1[CH:24]=[CH:23][CH:22]=[CH:21][C:20]=1[Cl:25]A mixture of 2-(2-chlorophenylamino)-3,4-difluoro-5-trimethylsilanylethynylbenzoic acid methyl ester (7.11 g, 18.1 mmol), HgSO4 (5.43 g, 18.1 mmol), and conc. H2SO4 (1.92 mL, 36.1 mmol) in acetone-water (150 mL/25 mL) was refluxed for 3 hours. The reaction mixture was concentrated in vacuo, diluted with EtOAc-THF, and washed with water and brine. The organic layer was dried over MgSO4, filtered, and concentrated in vacuo to give the crude material which was triturated with MeOH to afford the desired product (4.46 g, 73%).
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