[Cr](O[Cr]([O-])(=O)=O)([O-])(=O)=[O:2].[K+].[K+].C(N[C:16]1[CH:25]=[C:24]([NH:26][C:27](=[O:29])[CH3:28])[C:23]([O:30]C(=O)C)=[C:22]2[C:17]=1[CH:18]=[CH:19][C:20]([CH3:34])=[N:21]2)(=O)C>C(O)(=O)C.O>[C:27]([NH:26][C:24]1[C:23](=[O:30])[C:22]2[N:21]=[C:20]([CH3:34])[CH:19]=[CH:18][C:17]=2[C:16](=[O:2])[CH:25]=1)(=[O:29])[CH3:28]This compound was prepared by the oxidation of the corresponding acylamido with potassium dichromate in glacial acetic acid. Into a 1000 ml Erlenmeyer flask, 240 ml of glacial acetic acid, and 5,7-diacetamido-2-methyl-8-acetoxyquinoline (31) (prepared as described in Example 31) (6.3 g, 2.0 mmol) were added. To the resulting suspension, a solution of potassium dichromate (17.64 g) in 200 ml of water was added. This black solution was magnetically stirred at room temperature for 20-24 hours. The solution was then poured into 900 ml of water and extracted with dichloromethane (5×200 ml). The organic extracts were washed with a solution of 5% sodium carbonate in a saturated salt solution (3×300 ml). The organic layer was dried overnight with anhydrous magnesium sulfate. The magnesium sulfate was filtered off, and the solvent was evaporated to leave an orange/yellow solid. The solid 7-acetamino-2-methylquinoline-5,8-dione (27) was dried overnight under vacuum. 2.6 g of product was obtained for a yield of 56%.
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