3334-67-6

879-56-1

Compounds 1-3 (CAS: 3334-67-6) (40.0 g, 20.5 mmol) were taken as raw material and mixed with polyphosphoric acid (PPA) (100 mL) and the reaction was carried out with mechanical stirring at 90 °C for 3 hours. Upon completion of the reaction, the mixture was cooled to 60 °C and ice water (50 mL) was slowly added under stirring for 30 min. Subsequently, the mixture was extracted using ethyl acetate (EtOAc) (120 mL × 3). The organic phases were combined, washed sequentially with water (40 mL) and brine (40 mL), and then dried with anhydrous Na2SO4. After removal of the solvent under reduced pressure, the residue was purified by silica gel column chromatography (eluent: dichloromethane/methanol = 100/1 (v/v)) to afford the target product, 7-methoxy-2,3-dihydroquinolin-4(1H)-one (Compounds 1-4) (18 g, 50% yield), as a yellow solid. lc-MS (ESI): m/z 178 [M + H]+.