Hydrochloric Acid → 2-Methoxy-8,9-methylenedioxydibenzo[c,h]cinnoline

Participants

Reaction Steps

6-(2-Amino-4,5-methylenedioxyphenyl)-2-methoxynaphthalene 46 (170 mg, 0.58 mmol) was dissolved in acetic acid (4.5 mL) and concentrated hydrochloric acid (0.9 mL). The solution was cooled in an ice bath and diazotized by the dropwise addition of a solution of sodium nitrite (0.36 g in 3.6 mL water). The resulting diazonium solution was allowed to warm slowly to room temperature and left for 1 day. To the resulting red solution containing some precipitate was added 50 mL water and the mixture was extracted with ethyl acetate (30 mL×3). The organic layers were combined and washed with diluted sodium hydroxide solution first, then with water and brine. The organic layer was dried over anhydrous sodium sulfate and evaporated in vacuo. The crude product was purified by column chromatography on silica gel using 50:50 hexanes:ethyl acetate to give the pure 43 (20 mg) in 11% yield; mp 258-260° C.; IR (KBr) 2922, 1611, 1497, 1465, 1414, 1370, 1272, 1201 cm−1; UV (MeOH) 286, 228 nm (log ε=4.72, 4.41); 1H NMR (CDCl3) δ4.01 (3H, s), 6.23 (2H, s), 7.30 (1H, J=2.6), 7.48 (1H, dd, J1=9.1, J2=2.6), 7.75 (1H, s), 7.95 (1H, s), 8.00 (1H, d, J=9.2), 8.19 (1H, d, J=9.1), 9.62 (1H, d, J=9.2); 13C NMR δ56.01, 97.95, 102.88, 107.48, 108.31, 119.09, 119.61, 119.71, 120.57, 125.89, 126.56, 132.26, 134.59, 142.52, 145.88, 150.21, 152.14, 160.16; HRMS (EI) calcd for C18H12N2O3 m/z: 304.0848; found: 304.0843.

Provenance & Evidence