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- Title
Comprehensive theoretical study of nickel‐NHC‐catalyzed enantioselective intramolecular indole C—H cyclization: Reaction mechanism, reactivity, regioselectivity, and electronic processes.
- Authors
Wang, Fen; Chen, Changbao; Zhang, Feng; Meng, Qingxi
- Abstract
Density functional theory was used to illuminate the reaction mechanism of Ni(0)‐NHC‐catalyzed enantioselective intramolecular CH cyclization of indoles. The ωB97XD functional with 6‐31G(d,p) basis set (SDD for nickel) was employed to optimize all intermediates and transition states. The computations revealed that the reactivity of C1H bond was the best among all CH bonds of indole catalyzed by the Ni‐NHC complex, and in the C1H bond activation, the concerted oxidative addition was more dominant than the ligand‐to‐ligand H transfer reaction, due to the lower free energy barrier. The most favorable channels predicted theoretically went through the ligand‐to‐ligand H transfer reaction and reductive elimination, and two chiral products ((R)‐ and (S)‐tetrahydroindolizines) were coexisted as a result of similar transition states and little difference in free energy barrier. Hence, the model ligand L1 was not good for the regioselectivity. Nevertheless, another ligand L2, a chiral N‐heterocyclic carbene ligand, gave good regioselectivity, and it changed the rate‐determining step and generally decreased the free energies of transition states and intermediates.
- Subjects
FRIEDEL-Crafts reaction; RING formation (Chemistry); OXIDATIVE addition; REDUCTIVE elimination (Chemistry); ACTIVATION energy; DENSITY functional theory; INDOLE derivatives
- Publication
Applied Organometallic Chemistry, 2022, Vol 36, Issue 10, p1
- ISSN
0268-2605
- Publication type
Article
- DOI
10.1002/aoc.6851