3-Chlorobenzoperoxoic acid (9.3 mg, 0.041 mmol) was added to a solution of N-(5-cyano-4-((2-methoxyethyl)amino)pyridin-2-yl)-7-formyl-6-((4-methyl-2-oxopiperazin-1-yl)methyl)-3,4-dihydro-1,8-naphthyridine-1(2H)-carboxamide (Example 83, 20 mg, 0.039 mmol) in CHCl3 (0.1 ml) at 0° C. After stirring for 20 min, the mixture was warmed to room temperature and stirred for another 2 h. The reaction mixture was diluted with DCM and washed with sat. aq. NaHCO3. The aqueous layer was back-extracted with DCM (2×). The combined organic layers were dried over Na2SO4 and evaporated. The residue was triturated with Et2O to give the title compound as a light purple solid.
