One Cyano Group in 2,3,5,6-Tetracyanopyrazine

One cyano group of 59 is replaced under very mild conditions. For example, 2-methoxy-3,5,6-tricyanopyrazine (98) is formed in nearly quantitative yield when a solution of 59 in methanol is allowed to stand at room temperature for 2 hr. The reaction with better nucleophiles such as anilines is so exothermic that the temperature must be controlled by cooling or addition rate. Good yields of the monodisplacement products 99 are easily obtained. Still better 

Addition of primary amines can be monitored quite easily almost as one would do in a titration. This is possible because the hydrogen of the substitution product is acidic enough to be removed by excess amine, giving an intensely red anion. The transient red color formed during the addition of amine persists when 59 has been completely monosubstituted (74USP3814757). 

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