Nitric Acid → 2,9-Dimethyl-5-nitro-1,10-phenanthroline

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Neocuproine hydrochloride, hemihydrate (25.0 g, 99 mmol) was dissolved in 100 mL of concentrated nitric acid. 200 mL of concentrated sulfuric acid was added, and the reaction was heated at reflux for 2.5 hours, and then allowed to stand at room temperature for 8 days. The reaction mixture was then gradually added to a mixture of about 3 Kg of ice and 351 g (8.8 mole) of LiOH·H2O, while stirring with a glass rod. During the neutralization procedure, ice was added as necessary so that unmelted ice was always present during the neutralization, and the neutralization reaction was also simultaneously cooled by an acetone/ice bath. After the addition was completed, the pH of the reaction mixture was 12. The aqueous mixture was extracted two times with methylene chloride, first with 1000 mL, and then with 400 mL. The methylene chloride fractions were combined, and extracted once with 500 mL of distilled H2O. The methylene chloride phase was concentrated to a residue, and triturated with 500 mL of acetonitrile. The solid was filtered, washed with acetonitrile, and dried under vacuum to give 10.3 g of cream yellow solid, which was dissolved in 100 mL of refluxing acetonitrile, allowed to crystallize at room temperature, and was filtered to give 8.5 g (34%) of cream-yellow crystals, mp 184°-186° C. FDMS (m/e) 253M. Anal. calcd for C14H11N3O2 ·0.25 H2O: C, 65.23; H, 4.50; N, 16.30. Found: C, 65.57; H, 4.45; N, 16.27. The NMR and IR spectra were consistent with the assigned structure and the product was homogeneous by TLC.

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