反应详情

Lithium bis(trimethylsilyl)amide in hexane (0.7 mL, 0.7 mmol, 1M) was added to a solution of 4-bromo-3-methyl-1H-pyrazole (100 mg, 0.62 mmol) under the N2 at −78° C., and the mixture was allowed to warm to room temperature for a period of 2 hrs. The mixture was cooled again to −78° C., methyl chloroformate (0.7 mmol, 0.054 mL) was added drop wise, stirring was continued at −78° C., and the reaction was allowed to warm to room temperature and stirred for overnight. The reaction mixture was treated with NH4Cl, extracted with ethyl acetate, and the combined organic layers were washed with brine and dried over Na2SO4. The solvent was evaporated and the crude product was chromatographed on an ISCO with 10% EtOAc/Heptane, got 128 mg white solid as a 1:1 mixture of the title compound 299a and 4-bromo-3-methyl-pyrazole-1-carboxylic acid methyl ester.

1. temperatureThe mixture was cooled again to −78° C.
2. customwas continued at −78° C.
3. temperatureto warm to room temperature
4. stirringstirred for overnight
5. extractionextracted with ethyl acetate
6. washthe combined organic layers were washed with brine
7. dry with materialdried over Na2SO4
8. customThe solvent was evaporated
9. customthe crude product was chromatographed on an ISCO with 10% EtOAc/Heptane
10. additionas a 1:1 mixture of the title compound 299a and 4-bromo-3-methyl-pyrazole-1-carboxylic acid methyl ester