2.1.2. 1*H*-Cyclopenta[*b*]Naphthalene-1,3(2*H*)-Dione **EA4**

Diethyl naphthalene-2,3-dicarboxylate (10 g, 38.5 mmol, 1 eq., M = 272.30 g/mol) was suspended in extra dry EtOAc (24 mL) and NaH 95% in oil (2.44 g, 96.4 mmol, 2.5 eq.) was added. The reaction media was refluxed at 105 ◦C for 5 h. After cooling, the yellow solid was filtered off and thoroughly washed with a mixture of EtOH-Et2O 50/50. Treatment of this solid with 200 mL of a 1 M HCl solution under reflux for 1.5 h furnished a new solid. After cooling, the solid was filtered off, washed with water and recrystallized in toluene (200 mL). The product was obtained as a brown solid (6.9 g, 35.27 mmol, 91% yield). 1H nmR (CDCl3) δ: 3.38 (s, 2H), 7.66–7.75 (m, 2*H*), 8.10–8.13 (m, 2*H*), 8.52 (s, 2*H*); 13C nmR (CDCl3) δ: 46.7, 124.3, 129.7, 130.6, 136.4, 138.2, and 197.6; HRMS (ESI MS) m/z: theor: 196.0524 found: 196.0526 ([M]+. detected).
