[Br:1][C:2]1[CH:3]=[C:4]2[C:11]([C:12]([O:14]C)=[O:13])=[C:10]([C:16]3[CH:21]=[CH:20][C:19]([F:22])=[CH:18][CH:17]=3)[O:9][C:5]2=[N:6][C:7]=1[Cl:8].BrC1C=C2C=C(C3C=CC(F)=CC=3)OC2=NC=1Cl.[OH-].[Na+]>C(Cl)Cl.CC(O)=O.CO.C1COCC1>[Br:1][C:2]1[CH:3]=[C:4]2[C:11]([C:12]([OH:14])=[O:13])=[C:10]([C:16]3[CH:21]=[CH:20][C:19]([F:22])=[CH:18][CH:17]=3)[O:9][C:5]2=[N:6][C:7]=1[Cl:8]A 4:1 inseparable mixture of methyl 5-bromo-6-chloro-2-(4-fluorophenyl)furo[2,3-b]pyridine-3-carboxylate (2.38 g, 6.19 mmol) and 5-bromo-6-chloro-2-(4-fluorophenyl)furo[2,3-b]pyridine (0.265 g, 0.812 mmol) was taken up in a 1:1:1 mixture of MeOH (50 mL), THF (50 mL), 1M NaOH (50 mL). The entire mixture was heated in an oil bath to an internal temp of 65° C. This mixture was allowed to stir at this temp for 1 h. The solution was then concentrated to an aqueous mixture. This mixture was diluted with EtOAc and 1 M HCl (50 mL). The layers were separated and the aqueous layer was extracted with EtOAc (3×20 mL). The combined organic extracts were washed with water, brine, dried over Na2SO4, filtered and concentrated to give a white solid. This solid was adsorbed onto SiO2 and flashed on silica gel eluting with a 0-10% MeOH in DCM solution containing 1% AcOH to give 5-bromo-6-chloro-2-(4-fluorophenyl)furo[2,3-b]pyridine-3-carboxylic acid (1.85 g, 4.99 mmol, 81% yield). LCMS: m/e 371 (M+H)+ LCMS retention time: 3.30 min. (Column: Phenomenex-Luna 50×2.0 mm 3u. Solvent A=90% Water: 10% Methanol: 0.1% TFA. Solvent B=10% Water: 90% Methanol: 0.1% TFA. Start % B=0. Final % B=100. Gradient Time=4 min. Flow Rate=0.8 mL/min.).
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