反应详情

Sodium ethanolate solution was freshly prepared by dissolving sodium (240 mg) in ethanol (30 ml). 2H-Pyrazole-3,4-dicarboxylic acid diethyl ester (800 mg, 3.77 mmol) was dissolved in this sodium ethanolate solution (11 ml) and stirred for 10 min (r.t.), before ethyl iodide (1.4 g, 9 mmol) was added dropwise. After the completion of the addition, the mixture was heated to reflux until all starting material was consumed (1 h). The solvent was then evaporated, the residue was taken up in ethyl acetate and washed (water). The organic layer was dried (Na2SO4), evaporated, and the title compound (280 mg, 31%) was isolated from the mixture by column chromatography (silica gel, heptane:ethyl acetate=100:0-60:40). (The regioisomeric 1-ethyl-1H-pyrazole-3,4-dicarboxylic acid diethyl ester can also be isolated, and can be distinguished from the desired product by NOE-1H-NMR.) MS (m/e)=241.1 [M+H+].

1. additionAfter the completion of the addition
2. temperaturethe mixture was heated
3. temperatureto reflux until all starting material
4. customwas consumed (1 h)
5. customThe solvent was then evaporated
6. washwashed (water)
7. dry with materialThe organic layer was dried (Na2SO4)
8. customevaporated