General procedure for the synthesis of 5-acetamido-1-indanone from N-(2,3-dihydro-1H-inden-5-yl)acetamide: To a stirred solution of N-(2,3-dihydro-1H-inden-5-yl)acetamide (11.5 g, 65.7 mmol) in acetic acid: ethyl acetate (1:1, 200 ml) was slowly added dropwise to a solution of chromium trioxide (15 g) dissolved in water at 0 °C 151.11 mmol) dissolved in water. The reaction mixture was continued to be stirred at room temperature for 3 hours. After completion of the reaction, the mixture was diluted with water and extracted with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography with methanol/dichloromethane as eluent to afford the target product 5-acetamido-1-indanone (9 g, 85% yield) as a yellow solid. m/z = 190 [M + H]+ by LC-MS.
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