[Cl:1][C:2]1[C:7]([N+:8]([O-:10])=[O:9])=[CH:6][CH:5]=[C:4]([Cl:11])[C:3]=1[CH2:12][C:13]([OH:15])=O.[NH2:16][C:17]1[CH:22]=[CH:21][N:20]=[CH:19][C:18]=1[CH:23]=[O:24]>S(Cl)(Cl)=O.ClCCl.CCOC(C)=O>[Cl:1][C:2]1[C:7]([N+:8]([O-:10])=[O:9])=[CH:6][CH:5]=[C:4]([Cl:11])[C:3]=1[CH2:12][C:13]([NH:16][C:17]1[CH:22]=[CH:21][N:20]=[CH:19][C:18]=1[CH:23]=[O:24])=[O:15]A solution of (2,6-dichloro-3-nitro-phenyl)-acetic acid (15.0 g, 60.0 mmol) in thionyl chloride (60 mL) is refluxed for one hour. The solvent is removed by concentration; dry toluene is added and concentrated to thoroughly remove thionyl chloride. To the solution of acid chloride in dry dichloromethane (200 mL) is added (drop-wise) a solution of 4-amino-pyridine-3-carbaldehyde (6.6 g, 54 mmol) in dichloromethane (50 mL) and DIEDA (10.7 mL, 60 mmol). The mixture is at room temperature for 2 hours. The reaction mixture is diluted with EtOAc (300 ml) and washed with saturated K2CO3 and brine. The organic layer is dried, filtered and concentrated to give crude product. Recrystallization with dichloromethane/hexane results in the titled compound as a solid (18.2 g, 95.2%).
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