Triethylamine → 4-Methylbenzo[f]quinoxaline-2,3(1H,4H)-dione

Participants

Reaction Steps

A suspension of 6-bromo-2-methylamino-1-nitronaphthalene (2.81 g, 10 mmol) and triethylamine (1.40 ml, 10 mmol) in 150 ml of 96% ethanol was hydrogenated at room temperature and atmospheric pressure in the presence of 5% palladium-on-carbon (500 mg) for 1 h. The solution was filtered directly into 50 ml of 4M hydrochloric acid under a nitrogen atmosphere. The acidic filtrate was evaporated to dryness and the solid diaminonaphthalene hydrochloride was refluxed with oxalic acid dihydrate (1.5 g, 11.9 mmol) in 25 ml of 4M hydrochloric acid without further purification. After reflux for 2 h the mixture was cooled, and the solid product was isolated by filtration and washed with water, ethanol and ether to give 2.07 g (92%) of the title compound. M.p. 332.7° C. (ethanol); IR (KBr): 1685 cm-1 ; 1H-NMR (DMSO-d6): 3.60 (s, 3H, CH3), 7.33-7.93 (m, 5H, ArH), 8.37-8.60 (m, 1H, ArH), 12.13 (broad s, 1H, NH); MS m/z: 226 (M+, 100%).

Provenance & Evidence