反应详情

A mixture of 5-(2-oxo-ethyl)-pyrazine-2-carboxylic acid methyl ester (prepared as in Example 42, 330 mg, 1.83 mmol), p-toluenesulfonic acid monohydrate (35 mg, 0.184 mmol), trimethyl orthoformate (3 mL, 137 mmol), and methanol (10 mL) was heated under reflux for 90 min. The mixture was concentrated in vacuo to dryness, and the residue was further concentrated in vacuo to dryness from toluene (10 mL). The resulting residue was shaken with methylene chloride (25 mL) and a saturated aqueous sodium bicarbonate solution (10 mL). The aqueous phase was back-extracted with methylene chloride (10 mL). Each extract was washed with a saturated aqueous sodium chloride solution (5 mL). The combined organic layers were dried over sodium sulfate, filtered, and concentrated in vacuo to afford 5-(2,2-dimethoxy-ethyl)-pyrazine-2-carboxylic acid methyl ester (325 mg, 78%) as a yellow oil.

1. temperaturewas heated
2. temperatureunder reflux for 90 min
3. concentrationThe mixture was concentrated in vacuo to dryness
4. concentrationthe residue was further concentrated in vacuo to dryness from toluene (10 mL)
5. extractionThe aqueous phase was back-extracted with methylene chloride (10 mL)
6. washEach extract was washed with a saturated aqueous sodium chloride solution (5 mL)
7. dry with materialThe combined organic layers were dried over sodium sulfate
8. filtrationfiltered
9. concentrationconcentrated in vacuo