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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Tris(pentafluorophenyl)borane adducts of substituted imidazoles:conformational features and chemical behavior upon deprotonation
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Tris(pentafluorophenyl)borane adducts of substituted imidazoles:conformational features and chemical behavior upon deprotonation

机译：取代咪唑的三（五氟苯基）硼烷加合物：构象特征和去质子化后的化学行为

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Tris(pentafluorophenyl)borane adds to the donor nitrogen atom of 1,4,5-trimethyl-and 1-methyl-4,5-diphenyl-imidazole(5a,b)to yield the corresponding adducts 6a and 6b,respectively.Treatment of 1-methylbenzimidazole with B(C_6F_5)_3 or B(C_6H_5)_3 gave the related adducts 6c and 7,respectively.All four adducts were characterized by X-ray diffraction.In solution,the compounds 6 exhibit dynamic ~(19)F NMR spectra,each featuring 15 separate ~(19)F NMR resonances at low temperature.With increasing temperature a coalescence of the o-,in-and p-F signals of only a pair of-C_6F_5 signals is observed,leaving the set of five resonances of the third-C_6F_5 group unchanged.It required a further increase of the monitoring temperature to eventually observe the coalescence of the respective signals of all three-C_6F_5 groups.A DFT study revealed no specific intramolecular interactions of the F-C(Ar)substituents with other moieties of the molecules 6;a topological control is thus likely to have caused this remarkably specific dynamic behavior.Deprotonation of the compounds 6a and 6c at carbon atom C2 was achieved by treatment with methyl-lithium.The expected"Arduengo carbene anions"(8)are,however,not stable under the reaction conditions but rapidly react by an intramolecular nucleophilic aromatic substitution at one of the adjacent-C_6F_S groups to yield the heterotricyclic products 9.The respective benzimidazole-derived compound 9c was also characterized by an X-ray crystal structure analysis.
机译：三（五氟苯基）硼烷加到1,4,5-三甲基-和1-甲基-4,5-二苯基-咪唑（5a，b）的供体氮原子上，分别生成相应的加合物6a和6b。 1-甲基苯并咪唑与B（C_6F_5）_3或B（C_6H_5）_3分别给出相关的加合物6c和7，通过X射线衍射对所有四个加合物进行表征。在溶液中，化合物6表现出动态〜（19）F NMR光谱，每个在低温下均具有15个独立的〜（19）F NMR共振。随着温度的升高，仅观察到一对C_6F_5信号的o-，in-和pF信号的合并，从而留下了五个共振第三个C_6F_5基团未发生变化。需要进一步提高监测温度才能最终观察到所有三个C_6F_5基团的各自信号的合并.DFT研究表明，FC（Ar）取代基与其他部分之间没有特定的分子内相互作用。分子6中的分子;因此可能导致拓扑控制化合物6a和6c在碳原子C2上的去质子化反应是通过用甲基锂处理而实现的。预期的“ Arduengo卡宾阴离子”（8）在反应条件下不稳定，但通过与在相邻的C 6F_S基团之一上进行分子内亲核芳族取代以产生杂环三环产物9。还通过X射线晶体结构分析表征了各自的苯并咪唑衍生的化合物9c。

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