General procedure for the synthesis of 4-bromoisoquinoline 2-oxide from 4-bromoisoquinoline (Compound 13A): a chloroform (100 mL) solution of 4-bromoisoquinoline (4.16 g, 18.6 mmol) was added dropwise to a chloroform (100 mL) solution of 70% mCPBA (12.4 g, 50.3 mmol) over a period of 1 h at room temperature. The reaction mixture was stirred at room temperature for 18 h. The reaction mixture was washed with 1N NaOH solution (2 x 150 mL), dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to give an off-white solid compound 13A (4.23 g, 94% yield).1H NMR (400 MHz, CDCl3) δ 8.71 (s, 1 H), 8.43 (s, 1 H), 8.09 (d, 1 H) , J = 8 Hz), 7.70 (m, 3H).
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