N-bromobutanimide → 1-Bromo-4-hydroxy-7-(4-methoxy-phenoxy)-isoquinoline-3-carboxylic acid butyl ester

To a solid mixture of 7-(4-methoxy-phenoxy)-4-hydroxy-isoquinoline-3-carboxylic acid butyl ester (305 mg, 0.83 mmol) and N-bromosuccinimide (162 mg, 0.91 mmol) cooled with an ice bath was added acetonitrile (6 mL). Resulting mixture was stirred at 0° C. for 1.5 h and was concentrated. The residue was purified by silica gel chromatography (eluting with 10%-40% ethyl acetate in hexanes) to provide the title compound (217 mg). 1H NMR (200 MHz, CDCl3) δ 11.88 (s, 1H), 8.32 (d, J=9.0 Hz, 1H), 7.54 (d, J=2.4 Hz, 1H), 7.46 (dd, J=9.0, 2.4 Hz, 1H), 7.08 (d, J=9.4 Hz, 2H), 6.95 (d, J=9.8 Hz, 2H), 4.46 (t, J=7.0 Hz, 2H), 3.85 (s, 3H), 1.85 (m, 2H), 1.47 (m, 2H), 0.98 (t, J=7.4 Hz, 3H).