Ammonium Acetate → 1-Amino-5-(5-fluoro-2-methylphenyl)cyclohexen-3-one

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Reaction Steps

A solution of 5-(5-fluoro-2-methylphenyl)cyclohexane-1,3-dione (3.0 g) and ammonium acetate (3.1 g) in ethanol (50 ml) was heated under reflux for 14 hours. The solvent was distilled off under reduced pressure, and the residue was dissolved in ethyl acetate, washed successively with water and saturated brine and then dried over magnesium sulfate. The solvent was distilled off under reduced pressure to obtain 1-amino-5-(5-fluoro-2-methylphenyl)cyclohexen-3-one. This was dissolved in ethanol (70 ml) and toluene (120 ml), combined with 3-oxobutylaldehyde dimethyl acetal (4.1 g) and potassium hydroxide powder (0.57 g), and then heated under reflux. The mixture was combined with potassium hydroxide powder (0.12 g) after 30 minutes and with potassium hydroxide powder (0.12 g) and 3-oxobutylaldehyde dimethylacetal (0.33 g) after 1 hour and further with potassium hydroxide powder (0.12 g) after 1 hour and 30 minutes, and then stirred at the same temperature for 2 hours. After cooling, the solvent was distilled off under reduced pressure, and ethyl acetate was added. The organic layer was washed successively with water and saturated brine, and dried over magnesium sulfate. Ethyl acetate was distilled off under reduced pressure, and the residue was subjected to a silica gel column (ethyl acetate-hexane) to obtain a crystal which was then recrystallized from ethyl acetate-hexane to obtain 7-(5-fluoro-2-methylphenyl)-4-methyl-5,6,7,8-tetrahydroquinolin-5-one (1.5 g).

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