An efficient method was developed for the synthesis of pyrano[4,3-b]indol-1(5H)-ones, which uses a protic ionic liquid [HTBD⁺][TFE^–] as both the solvent and reaction promoter. The reactions could be efficiently carried out at atmospheric pressures of CO₂, and various pyrano[4,3-b]indol-1(5H)-ones bearing versatile functionalities were obtained in moderate to high yields (71–99%).

中文翻译：

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由质子离子液体促进的CO ₂和炔基吲哚高效合成吡喃并[4,3 - b ]吲哚-1（5 H）-酮

开发了一种高效的吡喃并[4,3 - b ]吲哚-1（5 H）-酮的合成方法，该方法使用质子离子液体[HTBD ⁺ ] [TFE ^– ]作为溶剂和反应促进剂。该反应可以在大气压的CO ₂压力下有效地进行，并以中等至高产率（71-99％）获得了具有多种功能的吡喃并[4,3 - b ]吲哚-1（5 H）-。