Trifluoromethanesulfonic acid → 3(-3-Cyclopropyl-[1,2,4]oxadiazol-5-yl)-8-bromo-4,5-dihydro-2,5,10b-triaza-benzo[e]azulene-6-one

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3-(3-Cyclopropyl-[1,2,4]oxadiazol-5-yl)-5-(2,4-dimethoxy-benzyl)-8-bromo-4,5-dihydro-2,5,10b-triaza-benzo[e]azulene-6-one (1.1 g, 2.0 mmol) was suspended in CH2Cl2 (6 mL), cooled in ice, and diluted slowly with trifluroacetic acid (4.7 mL). The resulting solution was treated at 5° C. with trifluoromethanesulfonic acid (266 μL, 3.0 mmol). The red solution was stirred at room temperature for 1.5 h. The mixture was then evaporated and dissolved in CH2Cl2 (10 mL), washed with sodium hydrogen carbonate (sat., 10 mL) and the organic layer was dried (Na2SO4) and evaporated. Trituration with EtOAc. Yield: 772 mg (100%). m/z 385/387 (M—H−).

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