General procedure for the synthesis of 7-hydroxy-5-methoxy-2,3-dihydro-1H-inden-1-one from 5,7-dimethoxyindanone: To a solution of 5,7-dimethoxyindanone (10.3 g, 54 mmol) in dichloromethane (100 mL) was slowly added a 1 M solution of boron trichloride (BCl3) (102 mL, 102 mmol) at 0 °C. The reaction system was kept at 0 °C and the resulting solution was stirred for 2.5 hours. Subsequently, the reaction mixture was slowly warmed to room temperature and stirring was continued for 2.5 hours. After completion of the reaction, the mixture was carefully poured into ice (100 g) to quench the reaction. The aqueous layer was extracted with dichloromethane and after combining the organic phases, the solvent was removed by distillation under reduced pressure to afford 7-hydroxy-5-methoxy-2,3-dihydro-1H-inden-1-one (9.3 g, 52 mmol) in 96% yield. The product was confirmed by nuclear magnetic resonance hydrogen spectroscopy (1H NMR, CDCl3): δ 2.7 (t, 2H), 3.1 (t, 2H), 3.9 (s, 3H), 6.3 (m, 1H), 6.5 (m, 1H), 9.2 (bs, 1H); mass spectrometry (MS, ES) showed the molecular ion peak m/z 179 (M + 1)+.
