反应详情

Sodium methoxide (6.5 ml) (30% by weight in methanol) was dissolved in methanol (75 ml) at room temperature. Dimethyl malonate (3.7 ml) was added dropwise at ambient temperature over a period of 20 minutes and the reaction stirred at ambient temperature for 1 hour. Methyl 3-aminopyrazine-2-carboxylate (5.0 g) was added in portions at ambient temperature over a period of 40 minutes. The reaction mixture was heated to reflux for 3 days, and then allowed to cool. The solvent was concentrated. The residue was dissolved in water and acidified with concentrated hydrochloric acid (36% by weight in water). The precipitate was isolated, washed with water, methanol and ethyl acetate, and dried under high vacuum to give 8-hydroxy-6-oxo-5,6-dihydro-pyrido[2,3-b]pyrazine-7-carboxylic acid methyl ester as a beige solid (4.16 g). 1H-NMR (d6-DMSO): 3.80 (s, 3H), 8.59 (s, 1H), 8.70 (s, 1H) ppm.

1. temperatureThe reaction mixture was heated
2. temperatureto reflux for 3 days
3. temperatureto cool
4. concentrationThe solvent was concentrated
5. dissolutionThe residue was dissolved in water
6. customThe precipitate was isolated
7. washwashed with water, methanol and ethyl acetate
8. customdried under high vacuum