BrBr.Br[CH2:4][C:5]([O:7][CH2:8][CH3:9])=[O:6].[Br:10][C:11]1[CH:12]=[C:13]2[C:23](=[CH:24][CH:25]=1)[O:22][C:16]1[CH:17]=[N:18][C:19]([Cl:21])=[CH:20][C:15]=1[C:14]2=[O:26].C1COCC1>C(OCC)C.[Zn]>[Br:10][C:11]1[CH:12]=[C:13]2[C:23](=[CH:24][CH:25]=1)[O:22][C:16]1[CH:17]=[N:18][C:19]([Cl:21])=[CH:20][C:15]=1[C:14]2([CH2:4][C:5]([O:7][CH2:8][CH3:9])=[O:6])[OH:26]
Bromine (0.072 ml, 1.4 mmol) was added to a suspension of zinc dust (1.41 g, 21.57 mmol) in diethyl ether (25 ml) at RT. After 5 minutes, ethyl 2-bromoacetate (1.202 ml, 10.8 mmol) was added drop wise over a time period of 10 minutes and the reaction mixture was heated to reflux for 2 hours. 7-Bromo-3-chloro-5H-chromeno[2,3-c]pyridin-5-one (2 g, 6.44 mmol) was added in one portion, followed by THF (25.00 ml) and the reaction mixture was heated to reflux for 30 minutes. The reaction mixture was quenched with aqueous saturated NH4Cl solution (20 mL) and water (20 mL) and stirred 30 min at RT. The solution was filtered and the organic phase was separated. The solvent was removed under educed pressure to afford ethyl 2-(7-bromo-3-chloro-5-hydroxy-5H-chromeno[2,3-c]pyridin-5-yl)acetate (2.5 g, 6.27 mmol, 97% yield).
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