反应详情

A solution of 1,4-dihydro-2-methoxy-6-methyl-4-(2,3-dichlorophenyl)-5-pyrimidinecarboxylic acid, ethyl ester (1.3 g., 3.8 mmole) in dichloromethane (10 ml.) is cooled to 0° and treated with pyridine (0.6 ml., 7.58 mmole) followed by ethyl chloroformate (0.4 ml., 4.0 mmole). The cooling bath is removed and the reaction is allowed to stir at room temperature overnight. The solvent is then stripped off to provide a colorless solid. This material is dissolved in tetrahydrofuran-methanol (10 ml. of 1:4 mixture) and treated with 2N hydrochloric acid (2 ml.). The reaction is allowed to stir at room temperature for 30 minutes and the solvent is then evaporated. The residue is extracted with ethyl acetate and the combined extracts are washed with sodium bicarbonate and brine. After drying over anhydrous magnesium sulfate, the solvent is stripped and the residue is crystallized from isopropyl ether to provide 1.25 g. of 3,6-dihydro-4-methyl-6-(2,3-dichlorophenyl)-2-oxo-1,5(2H)pyrimidinedicarboxylic acid, diethyl ester as a colorless solid; m.p. 139.5°-141°. TLC(silica gel; acetone/hexanes, 50:50) Rf =0.44.

1. customThe cooling bath is removed
2. customto provide a colorless solid
3. stirringto stir at room temperature for 30 minutes
4. customthe solvent is then evaporated
5. extractionThe residue is extracted with ethyl acetate
6. washthe combined extracts are washed with sodium bicarbonate and brine
7. dry with materialAfter drying over anhydrous magnesium sulfate
8. customthe residue is crystallized from isopropyl ether
9. customto provide 1.25 g