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A DFT Study of the Stereoselectivity of Cu(OTf)2 Catalyzed [3+2] Cycloaddition of Trifluoromethylated N­acylhydrazones and Isoprene: A Concerted Asynchronous Mechanism
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  • Jing Tang,
  • Dong-Hui Xu,
  • Xin Wang,
  • Xiang-Yang Liu,
  • Xin-Tong Su,
  • Jianmin Guo,
  • Bin Zhai,
  • Laicai Li
Jing Tang
Sichuan Normal University
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Dong-Hui Xu
Sichuan Normal University
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Xin Wang
Sichuan Normal University
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Xiang-Yang Liu
Sichuan Normal University
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Xin-Tong Su
Chengdu Tongneng Compressed Natural Gas Co., LTD
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Jianmin Guo
Sichuan Medical University
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Bin Zhai
Systems Engineering Research Institute of China State Shipbuilding Corporation
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Laicai Li
Sichuan Normal University
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Abstract

Pyrazolidines are very important compounds that widely exist in many natural products. Herein, we have employed high-level DFT calculations to systematically investigate the underlying mechanism of Cu(OTf)2 catalyzed [3+2] cycloaddition reactions that synthesis CF3­substituted pyrazolidines. About eight possible initial configurations of the [3+2] reaction is considered and all relevant reactants, transition states and products are optimized. Based on these structures, IRC paths and the wavefunction analysis, we concluded that the Cu(OTf)2 catalyzed [3+2] cycloaddition follow a concerted asynchronous mechanism. The C­N bond forms immediately after the formation of the C­C bond. Among all eight reaction paths, the energy barrier for the [3+2] reaction that lead to the CF3­substituted syn­pyrazolidine is the lowest one, ca. 3.2 kcal/mol, which might result in the diastereoselectivity that observed in experiment. We have also investigated the reaction processes that without Cu(OTf)2 molecule. The computational results indicate that the energy barriers that form the diastereoisomers are much closer and also larger than the Cu(OTf)2 catalyzed one. Therefore, Cu(OTf)2 catalyst plays an important role for the diastereoselectivity of the [3+2] cycloaddition reaction. Our present work not only gives the detail mechanism of the Cu(OTf)2 catalyzed [3+2] cycloaddition, but can also be helpful for the future designation of Cu(OTf)2 based cycloaddition processes.

Peer review status:ACCEPTED

18 Dec 2019Submitted to International Journal of Quantum Chemistry
19 Dec 2019Submission Checks Completed
19 Dec 2019Assigned to Editor
02 Jan 2020Reviewer(s) Assigned
02 Jan 2020Review(s) Completed, Editorial Evaluation Pending
02 Jan 2020Editorial Decision: Revise Minor
07 Jan 20201st Revision Received
07 Jan 2020Assigned to Editor
07 Jan 2020Submission Checks Completed
22 Jan 2020Reviewer(s) Assigned
01 Feb 2020Review(s) Completed, Editorial Evaluation Pending
03 Feb 2020Editorial Decision: Revise Major
01 Mar 20202nd Revision Received
02 Mar 2020Submission Checks Completed
02 Mar 2020Assigned to Editor
02 Mar 2020Reviewer(s) Assigned
17 Mar 2020Review(s) Completed, Editorial Evaluation Pending
17 Mar 2020Editorial Decision: Accept