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[摘要]：Water-sol. 4H-imidazoles, which represent redox- as well as pH-switchable functional dyes, are synthesized via a novel procedure. In a smooth reaction, phthalic anhydride reacts with an oxalic acid amidine yielding a 4H-imidazole. Analogously, but in lower yields, naphthalene-1,8-dicarboxylic anhydride and 2-sulfobenzoic anhydride can also be transformed into 4H-imidazoles. 4-Hydroxybenzoic acids do not form the expected 4H-imidazoles, which possess hydroxyaryl substructures. However, in the course of the cyclization-long-range prototropism sequence, 3 new quinone methides were obtained. This sequence could be adapted successfully for the synthesis of the corresponding thioxo derivs. The water-sol. 4H-imidazoles and the quinone methides proved to be multifunctional and switchable dyes. They show acidochromism and in addn., can be transformed into fluorescent leuco forms, which reoxidize when exposed to air. |
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