15N‐labelled pyridines are liquid‐ and solid‐state nuclear magnetic resonance (NMR) probes for chemical and biological environments because their 15N chemical shifts are sensitive to hydrogen‐bond and protonation states. By variation of the type and number of substituents, different target pyridines can be synthesized exhibiting different pK a values and molecular volumes. Various synthetic routes have been described in the literature, starting from different precursors or modification of other 15N‐labelled pyridines. In this work, we have explored the synthesis of 15N 15N‐labelled pyridines using a two‐step process via the synthesis of alkoxy‐3,4‐dihydro‐2H‐pyran as precursor exhibiting already the desired pyridine substitution pattern. As an example, we have synthesized 3,5‐dimethylpyridine‐15N (lutidine‐15N) as demonstrated by 15N‐NMR spectroscopy. That synthesis starts from methacrolein, propenyl ether, and 15N‐labelled NH4Cl as nitrogen source.

中文翻译：

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15 N 标记的 3,5-二甲基吡啶的合成

15N 标记的吡啶是用于化学和生物环境的液态和固态核磁共振 (NMR) 探针，因为它们的 15N 化学位移对氢键和质子化状态敏感。通过改变取代基的类型和数量，可以合成具有不同 pKa 值和分子体积的不同目标吡啶。文献中描述了各种合成路线，从不同的前体或其他 15N 标记的吡啶的修饰开始。在这项工作中，我们探索了使用两步法合成 15N 15N 标记的吡啶，通过合成烷氧基-3,4-二氢-2H-吡喃作为已经表现出所需吡啶取代模式的前体。例如，我们合成了 3，5-二甲基吡啶-15N（二甲基吡啶-15N），如15N-NMR光谱所示。该合成从甲基丙烯醛、丙烯醚和 15N 标记的 NH4Cl 作为氮源开始。