1,2-氮杂硼杂环戊二烯的芳构化 Claisen 重排反应。
The aromatic Claisen rearrangement of a 1,2-azaborine.
机构信息
Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467-3860, USA.
Université de Pau et des Pays de l'Adour, E2S UPPA/CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux IPREM UMR 5254, Hélioparc, 2 avenue P. Angot, 64053 Pau cedex 09, France.
出版信息
Org Biomol Chem. 2023 May 10;21(18):3778-3783. doi: 10.1039/d2ob02186b.
The first aromatic Claisen rearrangement of a 1,2-azaborine is described along with a quantitative kinetic comparison of the reaction of the azaborine with its direct all-carbon analogue. The azaborine A rearranged in a clean, regioselective fashion and reacted faster than the all-carbon substrate B at all temperatures from 140-180 °C. Activation free energies were extracted from observed first-order rate constants (A: Δ‡298K = 32.7 kcal mol; B: Δ‡298K = 34.8 kcal mol) corresponding to a twenty fold faster rate for A at observed reaction temperatures. DFT calculations show that the rearrangement proceeds a concerted six-membered transition state and that the electronic structure of the BN and CC rings is mostly responsible for the observed regioselectivity and relative reactivity.
首次描述了 1,2-氮杂硼杂环戊二烯的芳香族 Claisen 重排反应，并对氮杂硼杂环戊二烯与直接的全碳类似物的反应进行了定量动力学比较。氮杂硼杂环戊二烯 A 以干净、区域选择性的方式重排，并且在 140-180°C 的所有温度下比全碳底物 B 反应更快。从观察到的一级速率常数（A：Δ‡298K = 32.7 kcal mol；B：Δ‡298K = 34.8 kcal mol）中提取了活化自由能，这对应于在观察到的反应温度下 A 的速率快二十倍。DFT 计算表明，重排经历了协同的六元过渡态，并且 BN 和 CC 环的电子结构主要负责观察到的区域选择性和相对反应性。
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