General procedure for the synthesis of 4-hydroxy-1-indanone from hydrogenated cinnamic acid lactone: A mixture of aluminum chloride (90.0 g, 676 mmol) and sodium chloride was stirred at 150 °C until the solid was completely dissolved, followed by the slow dropwise addition of hydrogenated cinnamic acid lactone (20.0 g, 135 mmol). After the dropwise addition, the reaction mixture was warmed to 200 °C and stirred continuously for 1 hour. Upon completion of the reaction, the mixture was cooled to room temperature and slowly poured into ice water (500 mL), followed by filtration to collect the crude product. The crude product was purified by recrystallization to afford 4-hydroxy-1-indanone (19 g, 95% yield) as a gray solid. The structure of the compound was confirmed by the following spectral data: mass spectrum (ESI positive ion mode) m/z 149.5 [M + H]+; 1H NMR (400 MHz, CDCl3) δ (ppm): 7.41-7.38 (m, 1H), 7.24-7.19 (m, 1H), 6.80-6.79 (m, 1H), 6.78-6.77 (d , 1H, J = 4.0 Hz), 5.46 (br, 1H), 3.06-3.03 (m, 2H), 2.69-2.66 (m, 2H).
