title: Mechanisms for nickel(0)/N-heterocyclic carbene-catalyzed intramolecular alkene hydroacylation: insights from a DFT study.
abstract: 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.
authors.affiliation: College of Chemistry and Material Science, Shandong Agricultural University, Taian, Shandong, 271018, People's Republic of China. qingxim@sdau.edu.cn.
authors.forename: Qingxi
authors.initials: Q
authors.lastname: Meng
authors.affiliation: Department of Chemistry, Taishan University, Taian, Shandong, 271021, People's Republic of China.
authors.forename: Fen
authors.initials: F
authors.lastname: Wang
keywords: Alkene; DFT; Hydroacylation; N-heterocyclic carbene; Nickel