To a stirred solution of {1-[4-(6-oxo-8-phenyl-1,6-dihydro-9-oxa-1,2-diaza-cyclopenta[a]naphthalen-7-yl)-phenyl]-cyclobutyl}-carbamic acid tert-butyl ester (5 mg, 0.01 mmol) in EtOH (1 mL), was added sodium hypochlorite (10% aqueous solution, 0.4 mL) at RT. After 2 h, EtOAc and water were added. The resulting biphasic mixture was separated. The aqueous phase was extracted with EtOAc. The combined organic extracts were washed with water and brine, dried (Na2SO4), filtered, and concentrated in vacuo. The reaction was repeated with {1-[4-(6-oxo-8-phenyl-1,6-dihydro-9-oxa-1,2-diaza-cyclopenta[a]naphthalen-7-yl)-phenyl]-cyclobutyl}-carbamic acid tert-butyl ester (20 mg, 0.039 mmol) and aqueous sodium hypochlorite (2 mL) in EtOH (3 mL) with initial cooling in a cold water bath. After workup, the resultant residues were combined and subjected to flash chromatography (SiO2, gradient 20 to 40% EtOAc in cyclohexane) to afford the title compound (16 mg, 60%) as a white solid. LCMS (Method H): RT=4.39 min, [M+H]+=542/544.
