[CH3:1][O:2][C:3]1[CH:12]=[C:11]2[C:6]([CH2:7][CH2:8][NH:9][C:10]2=[O:13])=[CH:5][CH:4]=1.C1C(=O)N([Cl:21])C(=O)C1.C([O-])([O-])=O.[Na+].[Na+]>OS(O)(=O)=O>[Cl:21][C:12]1[C:3]([O:2][CH3:1])=[CH:4][CH:5]=[C:6]2[C:11]=1[C:10](=[O:13])[NH:9][CH2:8][CH2:7]2To a mixture of 7-methoxy-3,4-dihydroisoquinolin-1(2H)-one (1c, 13.0 g, 73.9 mmol) in conc. H2SO4 (120 mL) was added portionwise NCS (10.4 g, 77.6 mmol) at 0° C. The reaction mixture was warmed to room temperature and stirred overnight. The reaction mixture was poured onto ice-water (200 mL). The solution was basified with Na2CO3 (s) to pH 8. The reaction mixture was extracted with EtOAc (2×200 mL). The combined organic layers were washed with brine (300 mL), dried over Na2SO4 and concentrated under vacuum. The residue was purified by column chromatography (petroleum ether/EtOAc, 1:1) to give 8-chloro-7-methoxy-3,4-dihydroisoquinolin-1(2H)-one (1d, 7.8 g, 50%) as a yellow solid.
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