A new protocol based on a re-engineering approach has been developed for the efficient synthesis of pyrazolo[1,2-a]pyrazoles and pyrano[2,3-c]pyrazoles via an isocyanide-based four-component reaction of dialkyl acetylenedicarboxylates, isocyanides, and ethyl acetoacetate with hydrazine hydrate or phenylhydrazine. The reactions were carried out under solvent- and catalyst-free conditions at mild temperatures and short times in good yields.

中文翻译：

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一种重新设计的方法：在无溶剂条件下通过基于异氰酸酯的四组分反应合成吡唑并[1,2-a]吡唑和吡喃并[2,3-c]吡唑

已开发出一种基于重新设计方法的新协议，可通过基于乙酰基二羧酸二烷基酯的异氰酸酯四组分反应有效合成吡唑并[1,2-a]吡唑和吡喃并[2,3-c]吡唑，异氰化物和乙酰乙酸乙酯与水合肼或苯肼。反应在无溶剂和无催化剂的条件下，在温和的温度和短时间下以良好的收率进行。