Issue 37, 2020

Computational investigations of NHC-backbone configurations for applications in organocatalytic umpolung reactions

Abstract

Density functional theory (DFT) and multiconfigurational self-consistent field theory (MCSCF) methods are employed to investigate variation of the electronic properties of various N-heterocyclic carbenes. Alterations to the backbone by increased or decreased conjugation, heteroatom substitution in the NHC ring, and electron-donating or -withdrawing backbone substituents are modeled. The MCSCF calculations show extensive delocalization of both the highest occupied and lowest unoccupied molecular orbitals for NHCs with polymerizable backbone substituents. The free energies of the intermediates and transition structures for benzoin condensation are also shown to be sensitive to substitution of the NHC backbone. Taken together, these results imply great sensitivity of the reactivity of poly(NHC) catalysts to backbone modification at this moiety. Implications with respect to enhancement of poly(NHC)s employed in umpolung catalysis are discussed.

Graphical abstract: Computational investigations of NHC-backbone configurations for applications in organocatalytic umpolung reactions

Supplementary files

Article information

Article type
Paper
Submitted
19 Jun 2020
Accepted
11 Sep 2020
First published
14 Sep 2020

Org. Biomol. Chem., 2020,18, 7437-7447

Author version available

Computational investigations of NHC-backbone configurations for applications in organocatalytic umpolung reactions

K. M. Melancon and T. R. Cundari, Org. Biomol. Chem., 2020, 18, 7437 DOI: 10.1039/D0OB01267J

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