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To a stirred mixture of 6-amino-7-fluoro-3-methyl-3H-benzoimidazole-5-carboxylic acid methyl ester (6) (8.00 g, 34.16 mmol) and cesium carbonate (22.48 g, 68.31 mmol) in anhydrous anisole (76 mL) under nitrogen was added 4-bromo-2-chloroiodobenzene (1.60 g, 1.10 equiv., 4.88 mmol). The preformed catalyst, as prepared above, was then added to the mixture to provide a dark brown suspension, which was heated at 100±2° C., with stirring at 350 rpm. The reaction was monitored by HPLC analysis. After 41 hours, no 6-amino-7-fluoro-3-methyl-3H-benzoimidazole-5-carboxylic acid methyl ester (6) remained. The reaction mixture was cooled to about 80° C. and 1M sulfuric acid (40.99 mL 40.99 mmol) was added. Gas evolution was observed after 10 minutes and the rate of addition was controlled to moderate the effervescence. At the end of the addition the pH was between 7 and 8. Additional sulfuric acid (1M, 10.25 mL, 10.25 mmol) was then added to give mobile slurry with a pH of 0. The mixture was diluted with anisole (20 mL) and Celatom FW-14 filter agent was added. It was then filtered at about 80° C. through a water-wet pad of Celatom FW-14 filter agent and the cake was washed with anisole (1×40 mL+3×20 mL), then water (10 mL). The lower aqueous layer was separated and discarded and the organic layer was washed with 10% aqueous NaCl solution (2×40 mL). This was added to a sodium hydroxide (5.46 g, 68.3 mmol) in methanol (24 mL) and the mixture was heated at 65° C. with stirring. After 17.5 hours HPLC analysis indicated that the hydrolysis of the ester was complete and the slurry was cooled to 15° C., then filtered on a sinter. The solid was washed with water (4×24 mL), MTBE (24 mL), and acetonitrile (2×25 mL) and then dried at 45° C. in a vacuum oven to provide 11.07 g of 6-(4-bromo-2-chlorophenylamino)-7-fluoro-3-methyl-3H-benzoimidazole-5-carboxylic acid (7) as a fine pale brown solid (assay 93.7% by 1H NMR), actual wt 10.37 g (72.2% yield). 1H NMR (400 MHz, d6 DMSO) δ 3.85 (3H, s, NMe), 6.53 (1H, dd, J 9, 7, Ar—H), 7.27 (1H, dd, J 9, 2.5, Ar—H), 7.56 (1H, d, J 9, Ar—H), 7.97 (1H, s, Ar—H), 8.20 (1H, s, Ar—H), 11.5 (1H, s, CO2H). 13C NMR (100 MHz, d6 DMSO) δ 31 (CH3), 108 (CH, d, J 2), 109 (CH), 117 (C, d, J 6), 122 (C), 124 (C, d, J 7), 127 (C), 130 (C), 131 (C), 132 (C, d, J 9), 133 (C, d, J 11), 141 (C), 145 (CF, d, J 252), 146 (CH), 170 (C═O).
