An efficient and green protocol for the synthesis of 4‐aryl‐3,4‐dihydro‐2H,5H‐pyrano[3,2‐c]chromene‐2,5‐diones and 8‐aryl‐7,8‐dihydro‐6H‐[1,3]dioxolo[4,5‐g]chromene‐6‐ones through the Ag₂Cr₂O₇ nanoparticles catalyzed cyclocondensation reaction of active methylene compounds including 4‐hydroxycoumarin or 3,4‐methylenedioxyphenol, aromatic aldehydes, and meldrum's acid in water at ambient temperature was described. This method demonstrates several advantages compared with methods that are currently employed such as a mild reaction conditions, simple work‐up, good to excellent yields, avoiding toxic catalyst and hazardous solvent, and recovery and reuse of the catalyst.

中文翻译：

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Ag2Cr2O7纳米颗粒：一种环境友好且可重复使用的催化剂，用于在环境温度下在水性介质中合成吡喃并[c]铬代二酮和[1,3]二氧代[g]色酮。

一种高效且绿色的合成4-芳基-3,4-二氢-2 H，5 H-吡喃并[3,2 - c ]色烯-2,5-二酮和8-芳基-7,8-二氢的方案通过Ag ₂ Cr ₂ O _7生成-6 H ‐ [1,3] dioxolo [4,5‐ g ]色烯-6‐one描述了在环境温度下，纳米粒子在水中催化活性亚甲基化合物（包括4-羟基香豆素或3,4-亚甲基二氧基苯酚，芳族醛和me的酸）的环缩合反应。与目前采用的方法相比，该方法具有许多优势，例如反应条件温和，后处理简单，收率好至极好，避免了有毒的催化剂和有害溶剂以及催化剂的回收和再利用。