General procedure for the synthesis of 6-(methoxy)-3,4-dihydro-1(2H)-isoquinolinone from the compound (CAS:110192-21-7): the feedstock compound (35.0 g, 167.26 mmol) was slowly added to preheated polyphosphoric acid (184 mL, 183.99 mmol) at 120 °C, keeping the temperature at 120 °C. The reaction mixture was stirred at room temperature for 6 h. Subsequently, the reaction was quenched with ice water, alkalized with K2CO3 to pH neutral and extracted with dichloromethane (DCM). The organic layers were combined, dried with anhydrous Na2SO4, filtered and the solvent concentrated. The crude product was purified by silica gel column chromatography using ethyl acetate (EtOAc)/hexane (1:1) as eluent to afford the target product 6-(methoxy)-3,4-dihydro-1(2H)-isoquinolone (38.5 g, 218 mmol, 76% yield) as a white solid.1H NMR (500 MHz, CDCl3) δ 8.01 (d, J = 8.7 Hz, 1H), 6.90 (d, J = 8.7 Hz, 1H), 6.86 (dd, J = 8.7, 2.4 Hz, 1H), 6.71 (d, J = 2.4 Hz, 1H), 3.85 (s, 3H), 3.56 (td, J = 6.6, 2.8 Hz, 2H), 2.96 (t, J = 6.6 Hz, 2H); EI/ MS m/z 177.1 [M+].
