A synthesis of 2,3-diaryl-substituted pyrazolo[1,5-a]pyridines in moderate to good yields under metal-free and mild conditions is described. The intramolecular cyclization of the oxime substrates is mediated by PPh3/I2, which leads directly to pyrazolo[1,5-a]pyridines without the formation of a 2H-azirine intermediate. Various substituents on the aryl rings are compatible with the method.

中文翻译：

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三苯基膦/二碘介导的吡唑并[1,5-a]吡啶的温和高效合成

描述了 2,3-二芳基取代的吡唑并 [1,5-a] 吡啶在无金属和温和条件下以中等至良好的产率合成。肟底物的分子内环化是由 PPh3/I2 介导的，它直接导致吡唑并 [1,5-a] 吡啶而不形成 2H-氮丙啶中间体。芳环上的各种取代基都与该方法兼容。