Methyldiphenylamine → 6-[p-(Methylphenylamino)phenyl]-2,3,5-pyrazinetricarbonitrile

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A mixture of 18 g of tetracyanopyrazine and 18.3 g of N-methyl-N-phenylaniline in 200 ml of dimethylsulfoxide was heated at 100°C for 21 hours, the solution was cooled and poured onto 6 liters of ice water to give a sticky precipitate. The mixture was extracted with ethyl acetate. The ethyl acetate solution was back-extracted with water, dried over sodium sulfate and concentrated to give a dark brown solid. Unreacted tetracyanopyrazine was removed by recrystallization of the solid from toluene, from which TCP was the first to crystallize. The toluene solution was concentrated and the residue was rinsed with hexane to partially remove unreacted N-methyl-N-phenylaniline. The residue was dissolved in aqueous tetrahydrofuran (THF) (75% tetrahydrofuran) at 50°C, the THF removed by distillation, and the residual solid washed with water to remove water-soluble by-products. The remaining product was chromatographed on a column of neutral silicic acid using hexane/benzene/ acetonitrile eluents. Red fractions were combined, concentrated, and the product recrystallized from heptane-toluene to give 3.02 g of red-purple 6-[p-(methylphenylamino)phenyl]-2,3,5-pyrazinetricarbonitrile, mp 187.3°- 1.88.8°C after drying at 111°C (0.1 mm). Another 1.93 g of this product was recovered from mother liquors. Silica paper chromatography revealed only one colored product.

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