Pyridine → 2,3,6-trimethyl-4-(1H-pyrazol-5-ylimino)cyclohexa-2,5-dien-1-one

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Reaction Steps

A 1.62 ml quantity of pyridine was dissolved in 60 ml of dichloroethane, and 0.55 ml of titanium tetrachloride was added thereto. The mixture was refluxed with heating for 15 minutes. Then, to the mixture were added 1.50 g of 2,3,5-trimethyl-1,4-benzoquinone and 0.83 g of 3-aminopyrazole, and the mixture was refluxed with heating for 2 hours. The reaction mixture was cooled to room temperature and filtered through a Celite pad and the insoluble materials were washed there with chloroform. The filtrate was concentrated, and the resulting crude product was purified by silica gel column chromatography (eluent: diethyl ether-hexane=1:1), giving 0.52 g of 2,3,6-trimethyl-4-(3-pyrazolylimino)-2,5-cyclohexadien-1-one (Compound 37a) as a yellow solid. Table 3 below shows the structure and properties of Compound 37a.

Provenance & Evidence