Cl[C:2]1[CH:7]=[C:6]([C:8]([OH:10])=[O:9])[N:5]=[C:4]([C:11]([OH:13])=[O:12])[CH:3]=1.[NH:14]1[CH2:18][CH2:17][CH2:16][CH2:15]1>>[N:14]1([C:2]2[CH:7]=[C:6]([C:8]([OH:10])=[O:9])[N:5]=[C:4]([C:11]([OH:13])=[O:12])[CH:3]=2)[CH2:18][CH2:17][CH2:16][CH2:15]14-chloropyridine-2,6-dicarboxylic acid (0.238 mol, 48.0 g) is slowly added under stirring to a solution of pyrrolidine (0.952 mol, 67.8 g) at room temperature. Take care to avoid a too-fast addition leading to local temperature increase. Observe precipitation of a solid. The reaction mixture is heated at 120° C. for 2 hr. By gradually heating, the reaction mixture becomes solid. After cooling at 60° C., H20 (80 ml) is added and the mixture is stirred for 30 min until the solid is completely dissolved. The solution is then acidified with HCl (2M) until pH=1. The formed precipitate is filtered, washed twice H2O and dried overnight at 70° C. (93%).
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