A series of novel 3-methylphosphonylated [1,2,4]triazolo[4,3-a]pyridines was accessed through a 5-exo-dig-type cyclization of chloroethynylphosphonates and commercially available N-unsubstituted 2-hydrazinylpyridines. In addition, 3-methylphosphonylated [1,2,4]triazolo[4,3-a]quinolines and 1-methylphosphonylated [1,2,4]triazolo[3,4-a]isoquinolines were synthesized in a similar manner. The presence of a NO₂ group in the starting hydrazinylpyridine induces a Dimroth-type rearrangement leading to 2-methylphosphonylated [1,2,4]triazolo[1,5-a]pyridines.

中文翻译：

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通过5-exo-dig环化反应合成（[1,2,4]三唑并[4,3-a]吡啶-3-基甲基）膦酸酯及其苯并衍生物

一系列新的3- methylphosphonylated [1,2,4]三唑并[4,3的一个〕吡啶物通过5-访问外型-挖chloroethynylphosphonates和市售的N-未取代的2- hydrazinylpyridines的型环化。另外，以类似的方式合成了3-甲基膦酰化的[1,2,4]三唑并[4,3- a ]喹啉和1-甲基膦酰化的[1,2,4]三唑并[3,4- a ]异喹啉。起始肼基吡啶中NO ₂基团的存在引起Dimroth型重排，导致2-甲基膦酰化的[1,2,4]三唑并[1,5- a ]吡啶。