[Br:1][C:2]1[N:7]=[C:6]([C:8](O)=[O:9])[C:5]([O:11][CH2:12][C:13]2[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=2)=[C:4]([O:19][CH3:20])[CH:3]=1.C(Cl)(=O)C([Cl:24])=O>C1C=CC=CC=1.CN(C=O)C>[Br:1][C:2]1[N:7]=[C:6]([C:8]([Cl:24])=[O:9])[C:5]([O:11][CH2:12][C:13]2[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=2)=[C:4]([O:19][CH3:20])[CH:3]=1To a stirred mixture of 16 (2.54 g, 7.5 mmol) in benzene (30 mL) containing DMF (3 drops) was added oxalyl chloride (1.90 g, 15 mmol) in one portion. After gas evolution had ceased (about 45 min.), the now homogeneous solution was stirred an additional 15 min., then the solvent was evaporated. 1,2-Dichloroethane (30 mL) was added and again the solvent was evaporated to give a quantitative yield of 3 as a nearly colorless oil. This material was dissolved in CH2Cl2 (10 mL) or THF (10 mL) and used directly in subsequent coupling reactions. 6-BROMO-3-HYDROXYPICOLINIC ACID (17).
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