6-Bromo-2,3-Dihydroquinolin-4(1H)-One

90561-83-4

76228-06-3

a) 3-((4-bromophenyl)amino)propanoic acid (2.0 g, 11.6 mmol) and acrylic acid (0.95 mL, 13.9 mmol) were reacted in toluene (15 mL) for 3 days at 100 °C with stirring. After completion of the reaction, it was cooled to room temperature and the reaction mixture was extracted with 1N NaOH solution (150 mL). The aqueous layer was adjusted to a pH of about 3 with 2N HCl and subsequently extracted with ethyl acetate (2 x 100 mL). The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give N-(4-bromophenyl)-3-aminopropionic acid (1.65 g, 58% yield). The resulting carboxylic acid (1.64 g, 6.72 mmol) was mixed with polyphosphoric acid (30 g) and the reaction was stirred at 90 °C overnight. After completion of the reaction, it was cooled to room temperature and the reaction was quenched by the addition of ice water. The mixture was extracted with ethyl acetate (2 x 200 mL) and the organic layers were combined and washed sequentially with 1N NaOH solution, water and saturated brine. The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford the cyclization product 6-bromo-2,3-dihydroquinolin-4(1H)-one (0.88 g, 58% yield). The product was characterized by 1H NMR (d-chloroform), δ (ppm): 2.67 (t, 2H), 3.54 (t, 2H), 6.57 (d, 1H), 7.33 (dd, 1H), 7.92 (s, 1H).