The reaction of β-lactam carbenes with 3,6-dipyridyltetrazines: switch of reaction pathways by 2-pyridyl and 4-pyridyl substituents of tetrazines
作者:Xiao-Rong Wang、Juan Xing、Cai-Xia Yan、Ying Cheng
DOI:10.1039/c1ob06595e
日期:——
The reactions of β-lactam carbenes with both 3,6-di(2-pyridyl)tetrazine and 3,6-di(4-pyridyl)tetrazine were studied. It was found that β-lactam carbenes reacted with 3,6-di(2-pyridyl)tetrazine to produce 5-triazolo[1,5-a]pyridylpyrrol-2-ones in good yields, while with 3,6-di(4-pyridyl)tetrazine, they afforded pyrido[c]cyclopenta[b]pyrrol-2-ones in moderate yields. Both reactions were proposed to follow cascade mechanisms containing a 3,6a-dipyridylpyrrolo[3,2-c]pyrazol-5-one intermediate. The different pathways of the transformation of pyrrolo[3,2-c]pyrazol-5-ones were switched by the 2- and 4-pyridyl substituents. This work not only provided a simple and efficient strategy for the construction of novel triazolo[1,5-a]pyridine and pyrido[c]cyclopenta[b]pyrrole derivatives, respectively, but also revealed two different thermal transformation patterns of 3H-pyrazole compounds.
研究了δ-内酰胺碳化物与 3,6-二(2-吡啶基)四嗪和 3,6-二(4-吡啶基)四嗪的反应。研究发现,δ-内酰胺碳化物与 3,6-二(2-吡啶基)四嗪反应生成 5-三唑并[1,5-a]吡啶吡咯-2-酮,收率良好;而与 3,6-二(4-吡啶基)四嗪反应生成吡啶并[c]环戊并[b]吡咯-2-酮,收率中等。这两个反应都被认为遵循了含有 3,6a-二吡啶基吡咯并[3,2-c]吡唑-5-酮中间体的级联机制。吡咯并[3,2-c]吡唑-5-酮的不同转化途径由 2-和 4-吡啶基取代基切换。这项工作不仅为分别构建新型三唑并[1,5-a]吡啶和吡啶并[c]环戊并[b]吡咯衍生物提供了一种简单高效的策略,而且揭示了 3H 吡唑化合物的两种不同热转化模式。