反应详情

39 ml of tert-butanol, 27.44 ml (127.3 mmol) of diphenyl phosphorazidate and 17.7 ml (127.32 mmol) of triethylamine are added respectively to 10 g (63.66 mmol) of 5-nitro-1H-pyrazol-3-carboxylic acid. The solution is carried at reflux for 8 hours and then saturated aqueous potassium carbonate solution is added until pH=8 and the product is extracted several times with ethyl acetate. The organic phases are combined, dried on magnesium sulfate and concentrated. The residue obtained is triturated in methanol to yield 4.38 g (30.1%) of tert-butyl 5-nitro-1H-pyrazol-3-ylcarbamate in the form of a yellow solid. The filtrate is concentrated and purified by silica gel chromatography (eluent: 7:3 cyclohexane/ethyl acetate) to yield an additional 1.49 g (10.3%) of the desired product.

1. temperatureat reflux for 8 hours
2. extractionthe product is extracted several times with ethyl acetate
3. customdried on magnesium sulfate
4. concentrationconcentrated
5. customThe residue obtained
6. customis triturated in methanol