Phosphorus oxychloride → 5-Chloro-3,4-diazatricyclo(9.4.0.0,2,7)pentadeca-1(15),2(7),3,5,11,13-hexaene

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Reaction Steps

A mixture of the compound of formula (De), 6,7-dihydro-2H-benzo[6,7]cyclohepta[1,2-c]pyridazin-3(5H)-one (4.0 g, 19.3 mmol) and POCl3 (20 mL) was refluxed for 2 h. After cooling to ambient temperature, the volatiles were evaporated. The residue was poured into a mixture of ice water and sodium bicarbonate, CH2Cl2 (200 mL) was added to dissolve the solid. The layers were separated, and the aqueous layer was extracted with CH2Cl2 one more time. The combined organic layers were washed with brine. After being dried (MgSO4), filtered, and concentrated, the compound of formula (Df), 3-chloro-6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-c]pyridazine was obtained as a yellow solid (4.3 g, 99%), 1H NMR (300 MHz, CDCl3) δ: 7.82 (m, 1H), 7.45-7.24 (m, 4H), 2.59-2.51 (m, 4H), 2.27 (quant, J=6.9 Hz, 2H); LC-MS: purity: 100%; MS (m/e): 231 (MH+).

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