Substituent Effects Provide Access to Tetrasubstituted Ring-Opening Olefin Metathesis of Bicyclo[4.2.0]oct-6-enes.
Substituent Effects Provide Access to Tetrasubstituted Ring-Opening Olefin Metathesis of Bicyclo[4.2.0]oct-6-enes.
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取代基效应可访问bicyclo [4.2.0] oct-6-enes的四碱构成环的烯烃分解。
DOI：
10.1021/acsorginorgau.1c00016
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发表时间：
2021-10-06
期刊：
影响因子：
--
通讯作者：
Sampson NS
中科院分区：
文献类型：
--
作者：
Youn G;Sampson NS
在此，我们报告了在钌催化的交替开环易位聚合反应中含有α,β-不饱和酰胺部分的双环[4.2.0]辛-6-烯底物的意外反应性的起源。具体而言，与带有酯、烷基酮、腈或叔酰胺取代基的对照底物相比，带有弱酸质子的α,β-不饱和底物显示出由格鲁布斯型钌催化剂介导的开环复分解速率增加。 1H NMR和IR光谱分析表明α,β-不饱和酰胺底物的去质子化导致羰基与钌金属中心更强的配位。主成分分析确定环应变和羰基氧上的电子密度（基于通过 ωB97X-D/6311+G(2df,2p) 计算优化的结构）是双环[4.2.0]oct-6-烯快速开环复分解的两个关键因素；而偶极矩、共轭和最高占据分子轨道的能量对反应速率几乎没有影响。我们得出结论，双环[4.2.0]辛-6-烯与无张力环烯的交替开环复分解聚合反应需要可电离质子才能有效生成交替聚合物。
Herein, we report the origin of unexpected reactivity of bicyclo[4.2.0]oct-6-ene substrates containing an α,β-unsaturated amide moiety in ruthenium-catalyzed alternating ring-opening metathesis polymerization reactions. Specifically, compared with control substrates bearing an ester, alkyl ketone, nitrile, or tertiary amide substituent, α,β-unsaturated substrates with a weakly acidic proton showed increased rates of ring-opening metathesis mediated by Grubbs-type ruthenium catalysts. 1H NMR and IR spectral analyses indicated that deprotonation of the α,β-unsaturated amide substrates resulted in stronger coordination of the carbonyl group to the ruthenium metal center. Principal component analysis identified ring strain and the electron density on the carbonyl oxygen (based on structures optimized by means of ωB97X-D/6311+G(2df,2p) calculations) as the two key contributors to fast ring-opening metathesis of the bicyclo[4.2.0]oct-6-enes; whereas the dipole moment, conjugation, and energy of the highest occupied molecular orbital had little to no effect on the reaction rate. We conclude that alternating ring-opening metathesis polymerization reactions of bicyclo[4.2.0]oct-6-enes with unstrained cycloalkenes require an ionizable proton for efficient generation of alternating polymers.
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