Atom-efficient regioselective 1,2-dearomatization of functionalized pyridines by an earth-abundant organolanthanide catalyst
Atom-efficient regioselective 1,2-dearomatization of functionalized pyridines by an earth-abundant organolanthanide catalyst
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DOI：
10.1038/nchem.2087
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发表时间：
2014-12-01
期刊：
影响因子：
21.8
通讯作者：
Marks, Tobin J.
中科院分区：
文献类型：
--
作者：
Dudnik, Alexander S.;Weidner, Victoria L.;Marks, Tobin J.
开发地球资源丰富的非铂金属催化剂用于高价值的化学转化是当代化学合成的关键挑战。吡啶类化合物的脱芳是获得多种有价值的含氮天然产物、药物和材料的重要途径。在这里，我们报告了一个有效的1，2-区域选择性的有机镧系元素催化的吡啶脱芳构化过程中使用频哪醇硼烷，这是兼容的范围广泛的吡啶和官能团，并采用等摩尔试剂化学计量。关于该机制，从NMR光谱和动力学测量的速率定律的推导表明催化剂浓度中的一阶、吡啶浓度中的分数阶和频哪醇硼烷浓度中的逆一阶，其中C=N插入到La-H键中作为周转率确定。能量跨度分析提供了一个更详细的了解实验活动的趋势和不寻常的动力学行为，并提出了催化剂的“休息”状态和潜在的失活途径。
Developing earth-abundant, non-platinum metal catalysts for high-value chemical transformations is a critical challenge to contemporary chemical synthesis. Dearomatization of pyridine derivatives is an important transformation to access a wide range of valuable nitrogenous natural products, pharmaceuticals and materials. Here, we report an efficient 1,2-regioselective organolanthanide-catalysed pyridine dearomatization process using pinacolborane, which is compatible with a broad range of pyridines and functional groups and employs equimolar reagent stoichiometry. Regarding the mechanism, derivation of the rate law from NMR spectroscopic and kinetic measurements suggests first order in catalyst concentration, fractional order in pyridine concentration and inverse first order in pinacolborane concentration, with C=N insertion into the La-H bond as turnover-determining. An energetic span analysis affords a more detailed understanding of experimental activity trends and the unusual kinetic behaviour, and proposes the catalyst `resting' state and potential deactivation pathways.