反应详情

A suspension of ethyl 5-amino-1H-pyrazole-3-carboxylate (35.5 g, 229 mmol, prepared according to WO 2008015271), diethyl 2-acetylsuccinate (51.2 mL, 275 mmol) and TsOH.H2O (0.218 g, 1.144 mmol) in o-xylene (500 mL) was refluxed using a Dean-Stork condenser for 5 h. (Note: The suspension turned into a clear homogeneous solution and then in about 15 min a yellow solid started precipitated out of solution). Then, the reaction mixture was cooled, diluted with hexanes (250 mL), filtered, washed with hexanes and dried to afford ethyl 6-(2-ethoxy-2-oxoethyl)-7-hydroxy-5-methylpyrazolo[1,5-a]pyrimidine-2-carboxylate (53 g, 75% yield) as light yellow solid. 1H NMR (500 MHz, DMSO-d6) δ 12.61 (br. s., 1H), 6.49 (s, 1H), 4.34 (q, J=7.1 Hz, 2H), 4.09 (q, J=7.1 Hz, 2H), 3.57 (s, 2H), 2.34 (s, 3H), 1.33 (t, J=7.2 Hz, 3H), 1.19 (t, J=7.0 Hz, 3H). LCMS (M+1)=308.04.

1. temperaturewas refluxed
2. customfor 5 h.
3. customin about 15 min a yellow solid started precipitated out of solution)
4. temperatureThen, the reaction mixture was cooled
5. additiondiluted with hexanes (250 mL)
6. filtrationfiltered
7. washwashed with hexanes
8. customdried