Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction,The Journal of Organic Chemistry

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Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2020-10-28 , DOI: 10.1021/acs.joc.0c01790
Klaus Banert ₁ , Manfred Hagedorn ₁ , Manuel Heck ₁ , Raphael Hertel ₁ , Andreas Ihle ₁ , Ioana Müller ₁ , Tom Pester ₁ , Tharallah Shoker ₁ , Paul R. Rablen ₂

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A number of amines with three bulky alkyl groups at the nitrogen, which surpass the steric crowding of triisopropylamine considerably, were prepared by using different synthetic methods. It turned out that treatment of N-chlorodialkylamines with organometallic compounds, for example, Grignard reagents, in the presence of a major excess of tetramethylenediamine offered the most effective access to the target compounds. The limits of this method were also tested. The trialkylamines underwent a dealkylation reaction, depending on the degree of steric stress, even at ambient temperature. Because olefins were formed in this transformation, it showed some similarity with the Hofmann elimination. However, the thermal decay of sterically overcrowded tertiary amines was not promoted by bases. Instead, this reaction was strongly accelerated by protic conditions and even by trace amounts of water. Reaction mechanisms, which were analyzed with the help of quantum chemical calculations, are suggested to explain the experimental results.

中文翻译：

极高位阻性三烷基胺的合成及其通过霍夫曼样消除反应的衰变

通过使用不同的合成方法，制备了许多在氮上具有三个大烷基的胺，这些胺大大超过了三异丙胺的空间拥挤。原来，对氮的治疗-氯二烷基胺与有机金属化合物（例如格氏试剂）在大量过量的四亚甲基二胺的存在下提供了最有效的目标化合物。还测试了该方法的局限性。即使在环境温度下，取决于空间应力的程度，三烷基胺也经历脱烷基反应。因为在此转化过程中形成了烯烃，所以它与霍夫曼消除法有一些相似之处。但是，碱不能促进空间上拥挤的叔胺的热衰变。相反，质子条件甚至微量水强烈促进了该反应。建议通过量子化学计算来分析反应机理来解释实验结果。

更新日期：2020-11-06

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