6,7-dihydro-2H-benzo[6,7]cyclohepta[1,2-c]pyridazin-3(5H)-one

25742-87-4

25823-52-3

Using 4a,5,6,7-tetrahydro-2H-benzo[6,7]cyclohepta[c]pyridazin-3(4H)-one (4.7 g, 22 mmol) as starting material, it was mixed with anhydrous copper(II) chloride (6 g, 44 mmol) in acetonitrile (45 mL) and the reaction was carried out at reflux for 2 hours. After completion of the reaction, the mixture was cooled to room temperature and subsequently poured into ice water (200 g). The resulting solid was washed sequentially by 10% hydrochloric acid solution (~20 mL x 2) and cold water (~20 mL x 2). After freeze-drying treatment, the target product 3-oxo-6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-c]pyridazine (4.2 g, 90% yield) was obtained as a white solid. The product was characterized by 1H NMR (300 MHz, CDCl3): δ 10.80 (broad single peak, 1H), 7.53-7.21 (multiple peaks, 4H), 6.77 (single peak, 1H), 2.66 (triple peak, J = 6.9 Hz, 2H), 2.45 (triple peak, J = 6.9 Hz, 2H), 2.14 (quadruple peak, J = 6.9 Hz. 2H).LC-MS analysis showed 100% purity, mass spectrum (m/e): 213 (MH+).