Hexane → Diethyl alpha-methyl-5-phenylpyrazinylmalonate

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

A sodium hydride-mineral oil suspension (54%; 3.1 g., 0.069 mole) is stirred with three 50 ml. portions of dry hexane, each portion being pipetted out to remove the mineral oil. Dimethylformamide (30 ml., previously distilled and dried over a molecular sieve) is added through a pressure equalized addition funnel while a slow stream of nitrogen is passed through the mixture. The reaction vessel is cooled in an ice-bath while diethyl methylmalonate (12 g., 0.069 mole) is added dropwise to the stirred mixture. After the addition is complete, the ice-bath is replaced by an oil bath and the temperature is raised to 50° C. To the mixture is added dropwise 2-chloro-5--phenylpyrazine (10 g., 0.053 mole) in warm dimethylformamide (55 ml.). After this addition is complete, the mixture is heated for 31/2 hours during which time the temperature is raised to 120° C. The reaction mixture is cooled to about 80° C. and water (4 ml.) is added. The mixture is concentrated to a small volume, and the residual liquid is diluted with 50 g. of ice and extracted with ether several times. The combined ether extracts are washed with 5% hydrochloric acid, then with water, and then dried and evaporated. The resulting oil is chromatographed on a column of 500 g. of Merck acid-washed alumina. Elution with benzene-hexane (4:1) through ethyl acetate-benzene (1:3) yielded diethyl α-methyl-5-phenylpyrazinylmalonate.

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