[N:1]1[NH:2][C:3](=[O:16])[CH2:4][CH:5]2[CH2:11][CH2:10][CH2:9][C:8]3[CH:12]=[CH:13][CH:14]=[CH:15][C:7]=3[C:6]=12.[N+](C1C=C(S([O-])(=O)=O)C=CC=1)([O-])=O.[Na+].[OH-].[Na+].Cl>O>[O:16]=[C:3]1[NH:2][N:1]=[C:6]2[C:7]3[CH:15]=[CH:14][CH:13]=[CH:12][C:8]=3[CH2:9][CH2:10][CH2:11][C:5]2=[CH:4]1
Alternatively, a solution of 4a,5,6,7-tetrahydro-2H-benzo[6,7]cyclohepta[c]pyridazin-3(4H)-one (2.31 g, 10.74 mmol), sodium m-nitrobenzenesulfonate (2.48 g, 11 mmol), sodium hydroxide (1.86 g, 46.5 mmol) in water (80 mL) was heated under reflux for 1.5 h. The solution was cooled to ambient temperature, and then acidified with concentrated hydrochloric acid. The solid which precipitated was filtered off, washed with water and crystallized from ethanol to give 3-oxo-6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-c]pyridazine as tan crystals, 1.46 g; 1H NMR (DMSO-d6, 300 MHz) 13.04 (s, 1H), 7.25-7.45 (m, 4H), 6.78 (s, 1H), 2.49 (m, 2H), 2.35 (m, 2H), 2.04 (m, 2H) ppm; MS (ES) 213 (M+H).
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