Issue 27, 2020

BNN-1,3-dipoles: isolation and intramolecular cycloaddition with unactivated arenes

Abstract

The mono-base-stabilized 1,2-diboranylidenehydrazine derivatives featuring a 1,3-dipolar BNN skeleton are obtained by dehydrobromination of [ArB(Br)NH]2 (Ar = 2,6-diphenylphenyl (Dpp), Ar = 2,6-bis(2,4,6-trimethylphenyl)phenyl (Dmp) or Ar = 2,4,6-tri-tert-butylphenyl (Mes*)) with N-heterocyclic carbenes (NHCs). Depending on the Ar substituents, such species can be isolated as a crystalline solid (Ar = Mes*) or generated as reactive intermediates undergoing spontaneous intramolecular aminoboration of the proximal arene rings via [3 + 2] cycloaddition (Ar = Dpp or Dmp). The latter reactions showcase the 1,3-dipolar reactivity toward unactivated arenes at ambient temperature. In addition, double cycloaddition of the isolable BNN species with two CO2 molecules affords a bicyclic species consisting of two fused five-membered BN2CO rings. The electronic structures of these BNN species and the mechanisms of these cascade reactions are interrogated through density functional theory (DFT) calculations.

Graphical abstract: BNN-1,3-dipoles: isolation and intramolecular cycloaddition with unactivated arenes

Supplementary files

Article information

Article type
Edge Article
Submitted
16 Apr 2020
Accepted
19 Jun 2020
First published
19 Jun 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2020,11, 7053-7059

BNN-1,3-dipoles: isolation and intramolecular cycloaddition with unactivated arenes

R. Guo, J. Jiang, C. Hu, L. L. Liu, P. Cui, M. Zhao, Z. Ke, C. Tung and L. Kong, Chem. Sci., 2020, 11, 7053 DOI: 10.1039/D0SC02162H

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