Synthesis and Crystal Structures of Stable 4-Aryl-2-(trichloromethyl)-1,3-diaza-1,3-butadienes

A simple and convenient method to generate 4-aryl-substituted 1 H -2-(trichloromethyl)-1,3-diaza-1,3-butadienes from aryl(chlo­ro)methaniminium salts (best known as Vilsmeier–Haack reagents) and trichloroacetamidine has been developed. These 4-aryl-1 H -1,3-diaza­butadienes are isolable, relatively stable during silica gel chromatography, and can be crystallized. The analysis by X-ray diffraction demonstrated that in the solid state these 1,3-diazabutadienes have an s - cisoid conformation. The principal characteristic of these 1,3-diazabutadienes is their reactivity towards electron-deficient acetylenes, reacting under mild reaction conditions to produce 4-aryl-2-(trichloromethyl)pyrimidines in good yields.