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Sequence and Equivalent of Reagents Addition in NHC-Catalyzed Oxidative Nonpolar Inversion Enable Conversion from Aldimine to Benzoxazole
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  • Xiaoyan Li,
  • Jiabin Liu,
  • Qiao-Chu Zhang,
  • Wenjing Zhang,
  • Yu Lan
Xiaoyan Li
Zhengzhou University
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Jiabin Liu
Zhengzhou University
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Qiao-Chu Zhang
Zhengzhou University
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Wenjing Zhang
Zhengzhou University
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Yu Lan
Chongqing University
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Abstract

Mechanism of the oxidative nonpolar inversion reaction catalyzed by N-heterocyclic carbenes (NHCs) to achieve benzoxazoles was investigated in very details. The reaction was revealed to occur through five processes, and for oxidation in the second process, two successive tautomerizations followed by oxidation were demonstrated to be more energetically favorable than the other two pathways. The rate-determining step was disclosed to be the oxidation by 3,3’-5,5’-tetra-tert-butyl-4,4’-diphenoquinone (DQ). Afterwards, mechanism calculations to the non-catalyzed reaction was conducted and it was revealed that the excessive exothermic property of the initial step should be the main reason for the extremely high barrier in the following step. While with participation of NHC, this unfavorable transformation can be deftly prevented according to the specific sequence and amount of reagents addition, and therefore to enable the reaction to occur under mild conditions.

Peer review status:ACCEPTED

15 Feb 2020Submitted to International Journal of Quantum Chemistry
15 Feb 2020Submission Checks Completed
15 Feb 2020Assigned to Editor
20 Feb 2020Reviewer(s) Assigned
05 Mar 2020Review(s) Completed, Editorial Evaluation Pending
05 Mar 2020Editorial Decision: Revise Major
25 Mar 20201st Revision Received
25 Mar 2020Submission Checks Completed
25 Mar 2020Assigned to Editor
31 Mar 2020Reviewer(s) Assigned
31 Mar 2020Review(s) Completed, Editorial Evaluation Pending
31 Mar 2020Editorial Decision: Accept