Cycloaddition of pyridine N-imine with 6-alkyl-4-oxohex-5-ynoates followed by condensation with hydrazine provides concise access to pharmacologically active 6-(pyrazolo[1,5-a]pyridin-3-yl)pyridazinones. For the first time alkynyl heterocycles are also shown to be effective dipolarophiles for pyridine N-imine, and analogous compounds can be accessed directly in modest yields through the reaction of 6-(alkyn-1-yl)pyridazin-3-one derivatives.

中文翻译：

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通往吡唑并[1,5-a]吡啶-3-基哒嗪-3-酮的简明路线。

吡啶N-亚胺与6-烷基-4-氧合己烷-5-炔酸酯的环加成反应，然后与肼缩合，可轻松获得具有药理活性的6-（吡唑并[1,5-a]吡啶-3-基）吡啶并壬酮。炔基杂环也首次被证明是对吡啶N-亚胺有效的双极性亲和剂，并且可以通过6-（炔基-1-基）哒嗪-3-酮衍生物的反应直接以适当的收率得到类似的化合物。