The formation of 3-(2-nitrophenyl)pyruvic acid and its amide and ester derivatives – key compounds for the Reissert indole synthesis – was achieved under various reaction conditions via the acid catalyzed hydrolysis of 5-(2-nitrobenzyliden)-2,2-dimethyl-1,3-oxazolidin-4-one, which is readily available from 3-(2-nitrophenyl)oxirane-2-carboxamide. A new and highly efficient method for the synthesis of indole-2-carboxylic acid derivatives via the intramolecular reductive cyclization of o-nitrophenylpyruvic acid and its amide and ester derivatives was developed using Na₂S₂O₄ in dioxane/water at reflux.

中文翻译：

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基于Reissert反应合成3-（2-硝基苯基）丙酮酸衍生物和吲哚的新方法

3-（2-硝基苯基）丙酮酸及其酰胺和酯衍生物的形成是Reissert吲哚合成的关键化合物，是通过酸催化的5-（2-硝基苄基）-2,2在各种反应条件下实现的。-二甲基-1，3-恶唑烷丁-4-酮，其可容易地从3-（2-硝基苯基）环氧乙烷-2-甲酰胺获得。利用Na ₂ S ₂ O ₄在二恶烷/水中回流，开发了一种新的高效方法，该方法通过邻硝基苯基丙酮酸及其酰胺和酯衍生物的分子内还原环化反应合成吲哚-2-羧酸衍生物。