Tetrachloro isoindolinones

The methine type comprises isoindoline derivatives which, like tetrachloro-isoindolinone pigments, have only recently been described. One or usually two equivalents of a compound containing an activated methylene moiety are attached to one equivalent of isoindoline. The list of compounds featuring activated methylene groups includes cyanacetamide or heterocycles such as barbituric acid or tetrahydroquinolinedione. 

This represented a major breakthrough in the area of isoindolinone pigments, with much of the work done on tetrachloro isoindolinones at Geigy covered in an excellent comprehensive paper published by Pugin et al. [6]. 

The two tetrachloro isoindolinone moieties in compounds 4 are connected with each other via condensation with an appropriate aromatic or heterocyclic diamine. It is interesting to note that the aromatic substitution pattern of the bridging diamine has a strong influence on the color of the ensuing pigment... 

By virtue of their high-performance properties, azomethine-type tetrachloro-isoindolinone pigments 5 find extensive application in general and high-grade... 

---