Room temperature ring expansion of N-heterocyclic carbenes and B-B bond cleavage of diboron(4) compounds.
Room temperature ring expansion of N-heterocyclic carbenes and B-B bond cleavage of diboron(4) compounds.
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DOI：
10.1002/chem.201501498
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发表时间：
2015-06
期刊：
影响因子：
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通讯作者：
S. Pietsch;Ursula S. D. Paul;I. Cade;M. Ingleson;U. Radius;T. Marder
中科院分区：
文献类型：
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作者：
S. Pietsch;Ursula S. D. Paul;I. Cade;M. Ingleson;U. Radius;T. Marder
我们报告的分离和详细的结构表征，通过固态和溶液NMR光谱，中性单和双-NHC加合物的双（儿茶酚）二硼（B2目录2）。双-NHC加合物经历热诱导重排，通过C-N键断裂和NHC的环膨胀形成六元-B-C=N-C=C-N-杂环，而单-NHC加合物是稳定的。双（新戊基乙醇酸）二硼（B2 neop 2）比B2 cat 2在室温下反应性更强，产生扩环产物，表明NHC的扩环可能是一个非常容易的过程，对它们在催化中的应用具有重要意义。
We report the isolation and detailed structural characterization, by solid-state and solution NMR spectroscopy, of the neutral mono- and bis-NHC adducts of bis(catecholato)diboron (B2 cat2 ). The bis-NHC adduct undergoes thermally induced rearrangement, forming a six-membered -B-C=N-C=C-N-heterocyclic ring via C-N bond cleavage and ring expansion of the NHC, whereas the mono-NHC adduct is stable. Bis(neopentylglycolato)diboron (B2 neop2 ) is much more reactive than B2 cat2 giving a ring expanded product at room temperature, demonstrating that ring expansion of NHCs can be a very facile process with significant implications for their use in catalysis.