4.5 Article

Unraveling the mechanism and substituent effects on the N-heterocyclic carbene-catalyzed transformation reaction of enals and imines

期刊

MOLECULAR CATALYSIS
卷 519, 期 -, 页码 -

出版社

ELSEVIER
DOI: 10.1016/j.mcat.2022.112122

关键词

DFT method; N-heterocyclic carbene; Stereoselectivity; Mechanism

资金

  1. National Natural Science Foundation of China [21903072, 21773214]
  2. Natural Science Foundation for Excellent Young Sci-entist in Henan Province [212300410083]
  3. Training Plan for Young Teachers in Colleges and Universities in Henan Province [2020GGJS016]
  4. Outstanding Young Talent Research Fund of Zhengzhou University [1521316001]
  5. Startup Fund of Zhengzhou University of Light Industry [2017BSJJ036, 13501050087]

向作者/读者索取更多资源

This study reveals the mechanism and stereo-selectivity origin of NHC-catalyzed annulation of enals and imines through theoretical calculations. The presence of intramolecular hydrogen bond is crucial for the reaction, and non-covalent interaction analysis shows the bonding modes in the lower-energy transition state.
An intramolecular hydrogen bond-promoted activation of imines represents a new strategy in annulation re-actions catalyzed by N-heterocyclic carbenes (NHCs). In this study, the mechanism and the origin of stereo-selectivity in the NHC-catalyzed annulation of enals and imines are suggested and investigated theoretically. The computational results show that the reaction between a Breslow intermediate and an intramolecular hydrogen bond-activated imine is the rate-and stereoselectivity-determining step and results in the preferential generation of RS-configured products. The presence of intramolecular hydrogen bond is crucial for the reaction, because the formation of such bond significantly enhances the electrophilicity of the imine and thus facilitate the reaction. Non-covalent interaction (NCI) analysis shows that the C-H center dot & nbsp;center dot & nbsp;center dot & nbsp;pi, C-H center dot & nbsp;center dot & nbsp;center dot O, pi center dot & nbsp;center dot & nbsp;center dot pi, and lone pair (LP)center dot & nbsp;center dot & nbsp;center dot pi interactions contribute significantly to stabilizing the lower-energy transition state, thus inducing to the pref-erential formation of the RS-configured product.

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