31 июля, 2015 
Malyar Another approach to improve the color formation properties of Malachite Green lactone has been the introduction of nitrogen atoms into the phthalide ring. Thus, condensation ofpyridine-2,3-dicarboxylic acid anhydride with dimethylaniline in the presence of zinc chloride has been shown54 to yield a mixture of the 4- and 7-azaphthalides 11 and 12.
Stepwise addition of the aniline moieties in analogy to Scheme 7 (Route A) allows the preparation of asymmetrically substituted derivatives.55,56 The use of pyridine-3,4-dicarboxylic acid anhydride similarly results in the formation of mixtures of 5- and 6-azaphthalides.57 Quinoline-2,3-dicarboxylic anhydride has also been converted into the corresponding azaphthal — ides in a similar manner.58 Pyrazine-2,3-dicarboxylic acid anhydride yields
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4,7-diazaphthalides,59 and quinoxaline-2,3-dicarboxylic acid anhydride has also been shown60 to react analogously.
These azaphthalides have been reported to give blue or greenish-blue images, together with clay developers, and to have good color forming ability and resistance toward light and moisture.
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