[CH2:1]([O:3][C:4](=[O:12])[C:5]1[CH:10]=[CH:9][C:8]([NH2:11])=[CH:7][CH:6]=1)[CH3:2].[Br:13][C:14]1[CH:15]=[C:16]([CH:20]=O)[CH:17]=[N:18][CH:19]=1>C1(C)C=CC=CC=1.C1(C)C=CC(S(O)(=O)=O)=CC=1>[CH2:1]([O:3][C:4](=[O:12])[C:5]1[CH:10]=[CH:9][C:8]([N:11]=[CH:20][C:16]2[CH:17]=[N:18][CH:19]=[C:14]([Br:13])[CH:15]=2)=[CH:7][CH:6]=1)[CH3:2]A mixture of 4-amino-benzoic acid ethyl ester (8.06 g, 49 mmol), 5-bromo-pyridine-3-carbaldehyde (10 g, 54 mmol) and p-toluenesulfonic acid (190 mg, 1 mmol) in toluene (300 mL) was heated to reflux for 12 h. Then the reaction mixture cooled to room temperature. The solvent was removed in vacuo and the residue was washed with ether to afford 4-[(5-bromo-pyridin-3-ylmethylene)-amino]-benzoic acid ethyl ester (16.3 g, 100%) as a light yellow solid: LC/MS m/e calcd for C15H13BrN2O2 (M+H)+: 334.19, observed: 334.1.
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