反应详情

To 10 g (63.66 mmol) of 5-nitro-1H-pyrazole-3-carboxylic acid are respectively added 39 ml of tert-butanol, 27.44 ml (127.3 mmol) of diphenylphosphorazidate and 17.7 ml (127.32 mmol) of triethylamine. The solution is refluxed for 8 h, then an aqueous solution saturated with potassium carbonate is added until reaching pH 8, and the product is extracted several times with ethyl acetate. The organic phases are combined, dried over magnesium sulfate, and concentrated. The residue obtained is triturated in methanol to give 4.38 g of tert-butyl 5-nitro-1H-pyrazol-3-ylcarbamate in the form of a yellow solid. The filtrate is concentrated and purified by chromatography on silica (cyclohexane/ethyl acetate eluent: 7:3) to yield an additional 1.49 g of tert-butyl 5-nitro-1H-pyrazol-3-ylcarbamate in the form of a yellow solid.

1. temperatureThe solution is refluxed for 8 h
2. extractionthe product is extracted several times with ethyl acetate
3. dry with materialdried over magnesium sulfate
4. concentrationconcentrated
5. customThe residue obtained
6. customis triturated in methanol