Heterocyclic Substituted Azaphthalides

Color formers such as 16 and 17 and their mixtures are commonly known as Pyridyl Blues and are excellent products in combination with organic developers, yielding intense blue images with very high fastness properties. However, it has been observed71 that, for some applications, the 7-azaisomer is too reactive and hence it was desirable to modify the 

The possibility of replacing all three phenyl rings in the triarylmethane lactone structure by heterocycles has also been exploited. The first compound to be described83 was the 3,3-bisindolyl-7-azaphthalide (18). This 

Mixtures of 4- and 7-azaphthalides carrying a wide variety of heterocycles such as carbozolyl, pyrrolyl, acridinyl, phenothiazinyl, thianaph-thenyl, and thienyl as well as indolyl of the general formulas 19 and 20 have also been described.86 Table 1 illustrates the variety of hues available with such compounds. 

4-Azaphthalides carrying indolyl and indolizinyl substituents have been shown65 to produce blue color formers, while the combination of indoles 

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