[Cl:1][C:2]1[N:7]=[C:6]([NH2:8])[N:5]=[C:4]([NH2:9])[C:3]=1[N:10]=NC1C=CC(Cl)=CC=1>C(O)C.O.C(O)(=O)C.[Zn]>[Cl:1][C:2]1[N:7]=[C:6]([NH2:8])[N:5]=[C:4]([NH2:9])[C:3]=1[NH2:10]A suspension of 6-chloro-5-[(4-chlorophenyl)azo]-2,4-pyrimidinediamine (24.55 g, 0.0906 mol) in ethanol (640 ml), water (640 ml) and acetic acid (64 ml) was heated to 70° under nitrogen. Zinc dust (75 g) was added slowly over 1 hour, and then the reaction was stirred an additional hour at 70°. Then the reaction was cooled to room temperature and filtered under nitrogen. The filtrate was cooled to 0° and the pH was raised to 10 with 10% sodium hydroxide (400 ml). The precipitated zinc hydroxide was removed by filtration through Celite, and the dark red filtrate was neutralized to pH 7 with glacial acetic acid and concentrated to 300 ml. Water (50 ml) was added, the reaction was cooled to 0°, and the pH raised to 9 with 10% NaOH. The solution was allowed to stand at 5° for 3 days. The crystals were collected, washed with water (50 ml) and then ether (50 ml), and dried at 35° for 16 hours in vacuo to give 10.94 g of desired product.
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