7-Fluoro-1,2,3,4-tetrahydroquinoxalin-2-one → 7-fluoroquinoxalin-2(1H)-one

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Reaction Steps

A solution of 7-fluoro-3,4-dihydro-2(1H)-quinoxalinone (15.65 g, 92.88 mmol) in dichloromethane/methanol (1:1, 600 mL) was stirred with manganese dioxide (78.25 g) at room temperature for 1.5 h. The mixture was filtered through kieselguhr, washing through several times with 10% methanol/dichloromethane (˜1 L), and the filtrate was evaporated to give the product (7.27 g). Extraction of the residual filtration solids several times with dimethylformamide at 60-70° C., followed by filtration and evaporation of the extracts, gave more product (6.66 g), the total yield being 13.93 g (91.5%).

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