Pyridine → 2,6-Di-tert-butyl-4-[(pyrazin-2-yl)imino]cyclohexa-2,5-dien-1-one

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Reaction Steps

A 47 g quantity of 2,6-di-tert-butyl-1,4-benzoquinone and 20 g of aminopyrazine were added to 300 ml of tetrahydrofuran and dissolved therein with heating. To the solution was added a yellow suspension (which had been prepared by adding 12 ml of titanium tetrachloride dropwise with ice-cooling and stirring to a solution of 35 ml of pyridine in 200 ml of dichloroethane), and the mixture was refluxed with heating for 1 hour. To the reaction mixture was added a suspension of 70 ml of pyridine, 24 ml of titanium tetrachloride and 200 ml of dichloroethane. The resulting mixture was refluxed with heating for 2 hours. Again a suspension of 17 ml of pyridine, 6 ml of titanium tetrachloride and 100 ml of dichloroethane was added thereto and the resulting mixture was refluxed with heating for 30 minutes. Then, the reaction mixture was cooled to room temperature and filtered through a Celite pad and the insoluble materials were washed there with ethyl acetate. The filtrate was concentrated and the resulting crude product was purified by silica gel column chromatography (eluent: diethyl ether-hexane=1:10→1:1), and washed with cold hexane, thereby giving 58 g of 2,6-di-tert-butyl-4-pyrazinylimino-2,5-cyclohexadien-1-one (Compound 1a) as a yellow solid.

Provenance & Evidence