A novel approach was developed for the synthesis of 5H-isochromeno [4,3-b]indolizin-5-ones (ICIDOs) 3 through a cascade reaction of 1,2,3-indantriones 1 with ethyl 2-(pyridine-2-yl)acetates 2. Various 5H-isochromeno [4,3-b]indolizin-5-ones were produced by heating of the mixture of 1,2,3-indantriones and ethyl 2-(pyridine-2-yl)acetates for approximately 8 ?h in an environmentally-friendly PEG200 solvent with catalyst of a few drops of acetic acid. This approach has several advantages such as the use of an environmentally-friendly solvent, simple and practical operation (with filtration and washing and no column chromatography separation), good yields (up to 91%), use of commercially available raw materials, diverse target compounds, and products with potential biological activity.

中文翻译：

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1,2,3-茚满二酮与2-（吡啶-2-基）乙酸乙酯的环境无害级联反应，用于5 H-异色素[4,3-b]吲哚并五酮的位点选择性合成

通过1,2,3-indantriones 1与2-（吡啶-2-乙基）乙基的级联反应，开发了一种新的合成5H-异色素[4,3-b]吲哚嗪-5-酮（ICIDOs）3的方法。通过将1,2,3-茚满酮和2-（吡啶-2-基）乙酸乙酯乙酯的混合物加热约5，制得各种5H-异色素[4,3-b]吲哚嗪-5-酮。在环境友好的PEG200溶剂中，用几滴乙酸催化8 h。这种方法具有以下优点：使用环保溶剂，操作简单实用（具有过滤和洗涤功能，无需柱色谱分离），收率高（高达91％），使用可商购的原材料，目标多种化合物和具有潜在生物活性的产品。