[O:1]1CCO[C:2]21[CH2:21][C:10]1[CH:11]=[C:12]3[C:16](=[CH:17][C:9]=1[CH2:8][CH2:7][CH2:6]2)[N:15]([C:18](=[O:20])[CH3:19])[N:14]=[CH:13]3.C(O)CO.CC1C=CC(S(O)(=O)=O)=CC=1.[OH-].[K+]>C1(C)C=CC=CC=1>[C:18]([N:15]1[C:16]2[C:12](=[CH:11][C:10]3[CH2:21][C:2](=[O:1])[CH2:6][CH2:7][CH2:8][C:9]=3[CH:17]=2)[CH:13]=[N:14]1)(=[O:20])[CH3:19]1-Acetyl-5,7,8,9-tetrahydrocyclohepta[f]indazol-6(1H)-one (79) (30 g, 124 mmol) was added to a round bottom flask, equipped with a Dean Stark trap and condenser. Ethane-1,2-diol (27.6 mL, 495 mmol), pTSA (2.36 g, 12.38 mmol) and toluene (300 mL) were added and the resulting mixture was heated to about 142° C. for about 90 min. After cooling to rt, the mixture was concentrated and sonicated with water (˜50 mL). The resulting solids were collected by filtration and taken into MeOH (200 mL) and water (200 mL). Potassium hydroxide (13.9 g, 248 mmol) was added and the mixture was stirred at rt for about 30 min. The mixture was extracted with DCM (300 mL), washed with brine (200 mL), dried over MgSO4 and concentrated to afford 5,7,8,9-tetrahydro-M-spiro[cyclohepta[f]indazole-6,2′-[1,3]dioxolane] (81), (28.3 g, 93%); LC/MS, method 1, Rt=1.20 min, MS m/z 245 (M+H)+1H NMR (400 MHz, DMSO) δ 12.79 (bs, 1H), 7.93-7.87 (m, 1H), 7.44 (s, 1H), 7.22 (s, 1H), 3.97-3.76 (m, 4H), 3.06 (s, 2H), 2.91-2.81 (m, 2H), 1.91-1.81 (m, 2H), 1.70-1.59 (m, 2H).
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