Methyl 2-[3-(methoxy)-3-oxopropyl]benzoate (3.77 g, 16.98 mmol) was dissolved in anhydrous THF (75 mL) under argon protection. Under stirring, sodium hydride (2.04 g, 60% oil suspension, 50.9 mmol) was slowly added over 2 min. Subsequently, the reaction mixture was slowly heated to reflux. After 1 hour of reflux reaction, formation of a thick paste was observed. The reaction mixture was cooled to room temperature and quenched by adding water (1 mL) dropwise over 5 min. Next, the reaction mixture was acidified with 5 M hydrochloric acid (20 mL) and extracted twice with ethyl acetate. The organic phases were combined, dried with anhydrous magnesium sulfate, and subsequently concentrated under reduced pressure to give an oil. The oily substance was purified by silica gel column chromatography (70 g) using a 0-50% ethyl acetate/pentane gradient elution to afford methyl 1-oxo-2,3-dihydro-1H-indene-2-carboxylate as a yellow oil (2.14 g, 66% yield), which solidified to a solid on standing. The product was characterized by 1H-NMR (400 MHz, CDCl3): δ 7.79 (1H, d, J = 7.6 Hz), 7.63 (1H, dd, J = 7.6 and 7.6 Hz), 7.50 (1H, d, J = 7.6 Hz), 7.42 (1H, dd, J = 7.6 and 7.6 Hz), 3.80 (3H, s), 3.75 ( 1H, m), 3.60 (1H, m), 3.40 (1H, m).
