General procedure for the synthesis of 7-amino-2,3-dihydro-1-indenone from N-(3-oxo-2,3-dihydro-1H-inden-4-yl)acetamide: N-(3-oxo-2,3-dihydro-1H-inden-4-yl)acetamide (12.4 g, 0.065 mol) was dissolved in 6 N hydrochloric acid (150 mL), heated to 90 °C and the reaction was maintained for 3 hours. The progress of the reaction was monitored by thin layer chromatography (TLC) and after confirming the complete consumption of raw materials, the reaction mixture was cooled to room temperature. Subsequently, sodium carbonate (Na2CO3) was added in batches and the pH was adjusted dropwise to 8 by adding 2 M sodium hydroxide (NaOH) solution. the aqueous phase was extracted with ethyl acetate (EtOAc), the organic phases were combined, and dried over anhydrous sodium sulfate (Na2SO4). The organic phase was concentrated under reduced pressure to give 7-amino-2,3-dihydro-1-indanone (9.4 g, 98% yield) as a brown solid, which could be used for the subsequent reaction without further purification. m/z = 148.1 [M + H]+ by LC-MS.
