Electronic control of the reglochemistry in palladium - Phosphine catalyzed intermolecular heck reactions
Electronic control of the reglochemistry in palladium - Phosphine catalyzed intermolecular heck reactions
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DOI：
10.1021/ja0315098
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发表时间：
2004-06-09
影响因子：
15
通讯作者：
Brown, JM
中科院分区：
文献类型：
--
作者：
Deeth, RJ;Smith, A;Brown, JM
用密度泛函理论计算了中性[Pdl（PH 3）（vinyl）（RCHCH 2）]和阳离子[Pd（H2 PCH 2 PH 2）（vinyl）（RCHCH 2）]（+）（R = OMe，Me，and CN）单取代eta（2）-烯烃与eta（1）-乙烯基C-C偶联反应的过渡态结构和反应势垒，结果表明，过渡态结构和反应势垒主要依赖于区域化学，而不依赖于烯烃取代基的起始位置.因此，区域化学隐含在前体络合物的电子结构中。一个选择性指数，欧米茄，基于静电和前线轨道相互作用给出了一个很好的相关性与实验乙烯化或芳基化。该模型正确地预测，区域化学为R = OMe，Me，CN是相同的中性和阳离子Pd配合物，而R = CH 2 OH的区域化学反转。后者证实了明确的过渡态能量的计算。计算了13个取代基的选择性指数：CO2 Me，CN，CF 3，Ph，H，Me，CH 2 OH，CH 2NMe 2，2-吡咯烷酮，CH 2SiMe 3，OAc，OMe和F。阳离子条件系统地给出较大的Q值，因此倾向于有利于在烯烃上的α碳上的偶联。ω值近似为加性，可用于预测二取代烯烃的区域化学。
Density functional theory calculations of the transition-state structures and reaction barriers for the C-C coupling between monosubstituted eta(2)-olefins and eta(1)-vinyl for neutral [Pdl(PH3)(vinyl)(RCHCH2)] and cationic [Pd (H2PCH2PH2)(vinyl)(RCHCH2)](+) (R = OMe, Me, and CN) depend mostly on the regiochemistry and not on the starting position of the olefin substituent. The regiochemistry is thus implicit in the electronic structure of the precursor complex. A selectivity index, Omega, based on electrostatic and frontier orbital interactions gives a good correlation with experiment for vinylations or arylations. The model correctly predicts that the regiochemistry for R = OMe, Me, and CN is the same for both neutral and cationic Pd complexes while for R = CH2OH the regiochemistry reverses. The latter is confirmed by explicit calculations of the transition-state energies. Selectivity indices are computed for 13 substituents: CO2Me, CN, CF3, Ph, H, Me, CH2OH, CH2NMe2, 2-pyrolidone, CH2SiMe3, OAc, OMe, and F. Cationic conditions systematically give larger Q values and thus tend to favor coupling at the a carbon on the olefin. The Omega values are approximately additive and can be used to predict the regiochemistry for disubstituted olefins.