The Introduction of OH and COOH Groups into 4<i>H</i>-Imidazoles: Water-Soluble Functional Dyes and Quinomethides
作者:Rainer Beckert、Martin Matschke、Lenka Kubicova、Christoph Biskup
DOI:10.1055/s-2008-1067249
日期:2008.9
Water-soluble 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 oxalic acid amidine 5 yielding 4H-imidazole 1a. Analogously, but in lower yields, naphthalene-1,8-dicarboxylic anhydride and 2-sulfobenzoic anhydride can be transformed into 4H-imidazoles 1b,c. 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, the new quinomethides 7a-c were obtained. This sequence could be adapted successfully for the synthesis of corresponding thioxo derivatives 7d. The water-soluble 4H-imidazoles 1a-c as well as quinomethides of type 7 proved to be multifunctional and switchable dyes. They show acidochromism and in addition, can be transformed into fluorescent leuco forms, which reoxidize when exposed to air.
水溶性 4H-咪唑,代表氧化还原和 pH 可切换的功能染料,是通过一种新的方法合成的。在顺利的反应中,邻苯二甲酸酐与草酸脒 5 反应生成 4H-咪唑 1a。类似地,1,8-萘二甲酸酐和2-磺基苯甲酸酐可以转化为4H-咪唑1b,c,但产率较低。 4-羟基苯甲酸不会形成预期的具有羟基芳基子结构的4H-咪唑。然而,在环化-长程向质子序列过程中,获得了新的喹诺酮化合物7a-c。该序列可以成功地用于合成相应的硫代衍生物7d。水溶性 4H-咪唑 1a-c 以及 7 型喹甲基化物被证明是多功能且可转换的染料。它们表现出酸变色性,此外,可以转化为荧光无色形式,当暴露在空气中时会重新氧化。