Abstract 1-Phenyl-2-pyrazolin-5-ones 1 a–e react with tetracyanoethylene forming the corresponding dicyanomethylenepyrazolin-5-ones 2 a–e. The products are deeply coloured with absorption bands between 550 and 650 nm, but low ε-values and negative solvatochromic effect. By amine-HCN exchange reaction with anilines the red-coloured phenylamino-cyanomethylene-pyrazolinones 3–6 are obtained. 15 N-and 13 C-NMR-data ...
