Trimethyl orthoformate → 1-(2-cyclopropyl-3-fluoro-5-nitrophenyl)-1H-tetrazole

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A mixture of 2-cyclopropyl-3-fluoro-5-nitroaniline (300 mg, 1.53 mmol, 1 equiv), trimethylsilyl azide (1.0 mL, 7.65 mmol, 5 equiv), trimethylorthoformate (1.67 mL, 15.29 mmol, 10 equiv) in AcOH (3 mL) was heated to 70° C. and stirred for 7 hours behind a blast shield. After allowing to cool to room temperature, the mixture was further cooled in ice-water and basified to ca. pH 12-14 with 1N NaOH and diluted with EtOAc. The aqueous and organic layers were partitioned and the aqueous extracted with EtOAc (2×150 mL). The combined organic extracts were washed with 1N NaOH (1×100 mL), dried (Na2SO4), filtered, and the solvent removed under vacuum—silica gel was added at this stage so that the crude product was absorbed directly on to silica gel. The crude product was purified by column chromatography on silica gel using EtOAc/hexanes (30-50% EtOAc in increments of 10% EtOAc) to give the product 1-(2-cyclopropyl-3-fluoro-5-nitrophenyl)-1H-tetrazole (343 mg, 90%) as a white solid.

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