The problem of synthesising esters of fluorescein dyes has long been solved for the mother compound and its derivatives. The choice of an optimal method depends on the substituents in the xanthenes moiety and in the phthalic acid residue. To obtain alkyl esters of 4,5-dinitrofluorescein, we used thionyl chloride in ethanol. However, several other products appeared, which were identified as reduced species resulting from hydride transfer. A similar picture was observed when using sulphuric acid instead of thionyl chloride. The formation of reduced species was demonstrated by hydrogen-1 and carbon-13 nuclear magnetic resonance spectroscopy and X-ray analysis. In methanol, on the other hand, the esterification of the carboxylic group proceeds easily and with good yield. In the course of the current study, four new compounds of the fluorescein series were synthesised and characterised. The results show that nitro substitution in xanthenes favours dye reduction.

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4,5-二硝基荧光素酯合成的特点：还原物种的形成

荧光素染料酯类的合成问题早已解决了母体化合物及其衍生物的难题。最佳方法的选择取决于呫吨部分和邻苯二甲酸残基中的取代基。为了获得 4,5-二硝基荧光素的烷基酯，我们在乙醇中使用亚硫酰氯。然而，出现了几种其他产物，它们被确定为氢化物转移导致的还原物质。当使用硫酸代替亚硫酰氯时，观察到了类似的情况。通过氢 1 和碳 13 核磁共振光谱和 X 射线分析证明了还原物质的形成。另一方面，在甲醇中，羧基的酯化反应容易进行并且收率良好。在目前的学习过程中，合成和表征了四种荧光素系列的新化合物。结果表明，呫吨中的硝基取代有利于染料还原。