Phosphorus oxychloride → 4-Bromo-1,7-dichloroisoquinoline

4-bromo-7-chloroisoquinoline 2-oxide (3-7) (1.2 g, 4.64 mmol, 1.0 equiv.) was dissolved in anhydrous CHCl3 (20 mL) and treated dropwise with phosphorus oxychloride (0.649 mL, 6.96 mmol, 1.5 equiv.). The reaction mixture was refluxed at 66° C. LCMS after 3 hours showed only product. The reaction mixture was diluted with ethyl acetate, washed with saturated NaHCO3, and the organic layer was dried over Na2SO4, filtered and concentrated. The residue was triturated with hexane, and filtered to afford the product 3-8. LRMS m/z (M+H) 277.9 found, 277.9 required.