Meng Qingxi, Wang Fen
College of Chemistry and Material Science, Shandong Agricultural University, Taian, Shandong, 271018, People's Republic of China.
Department of Chemistry, Taishan University, Taian, Shandong, 271021, People's Republic of China.
J Mol Model. 2017 Jan;23(1):11. doi: 10.1007/s00894-016-3186-7. Epub 2016 Dec 21.
Density functional calculations have been applied to study and elucidate nickel(0)/N-heterocyclic carbene-catalyzed intramolecular alkene hydroacylation. The calculations showed that nickel(0)-catalyzed intramolecular alkene hydroacylation involved four potential reaction channels (I, II, III, and IV), and pathway IV was predicted to be more favorable than the other three. Two pathways, I and II, had three steps (oxidative addition, hydrogen migration, reductive elimination), and the rate-determining step was hydrogen migration. Pathway III proceeded through oxidative cyclization, β-hydride elimination, and hydrogen migration, and the rate-determining step was β-hydride elimination. Pathway IV included four steps (oxidative cyclization, dimerization, β-hydride elimination, hydrogen migration), and the rate-determining step was again β-hydride elimination. Oxidative cyclization was easy and led to rapid dimerization, greatly reducing the free energy of β-hydride elimination. The binuclear nickelacycle intermediate was observed in Ogoshi's experiments, and it was identified by nuclear magnetic resonance (NMR). The dominant product was the five-membered benzocyclic ketone p1. All results agreed with Ogoshi's experiments. Graphical Abstract Nickel(0)-catalyzed intramolecular alkene hydroacylation involved four potential reaction channels. The binuclear nickelacycle intermediate was important, and the dimerization greatly reduced the free energy of the β-hydride elimination.
密度泛函计算已被用于研究和阐释镍(0)/N-杂环卡宾催化的分子内烯烃氢酰化反应。计算结果表明，镍(0)催化的分子内烯烃氢酰化反应涉及四个潜在反应通道（I、II、III和IV），预计通道IV比其他三个通道更有利。通道I和II有三个步骤（氧化加成、氢迁移、还原消除），速率决定步骤是氢迁移。通道III通过氧化环化、β-氢消除和氢迁移进行，速率决定步骤是β-氢消除。通道IV包括四个步骤（氧化环化、二聚化、β-氢消除、氢迁移），速率决定步骤同样是β-氢消除。氧化环化很容易发生并导致快速二聚化，大大降低了β-氢消除的自由能。在小越的实验中观察到了双核镍环中间体，并通过核磁共振（NMR）对其进行了鉴定。主要产物是五元苯并环酮p1。所有结果与小越的实验一致。图形摘要：镍(0)催化的分子内烯烃氢酰化反应涉及四个潜在反应通道。双核镍环中间体很重要，二聚化大大降低了β-氢消除的自由能。
