Cobalt-Mediated Photochemical C−H Arylation of Pyrroles

Julia Märsch, Sebastian Reiter, Thomas Rittner, Rafael E. Rodriguez-Lugo, Maximilian Whitfield, Daniel J. Scott, Roger Jan Kutta, Patrick Nuernberger, Regina de Vivie-Riedle, Robert Wolf

Research output: Contribution to journalArticlepeer-review

Abstract

Precious metal complexes remain ubiquitous in photoredox catalysis (PRC) despite concerted efforts to find more earth-abundant catalysts and replacements based on 3d metals in particular. Most otherwise plausible 3d metal complexes are assumed to be unsuitable due to short-lived excited states, which has led researchers to prioritize the pursuit of longer excited-state lifetimes through careful molecular design. However, we report herein that the C−H arylation of pyrroles and related substrates (which are benchmark reactions for assessing the efficacy of photoredox catalysts) can be achieved using a simple and readily accessible octahedral bis(diiminopyridine) cobalt complex, [1-Co](PF6)2. Notably, [1-Co]2+ efficiently functionalizes both chloro- and bromoarene substrates despite the short excited-state lifetime of the key photoexcited intermediate *[1-Co]2+ (8 ps). We present herein the scope of this C−H arylation protocol and provide mechanistic insights derived from detailed spectroscopic and computational studies. These indicate that, despite its transient existence, reduction of *[1-Co]2+ is facilitated via pre-assembly with the NEt3 reductant, highlighting an alternative strategy for the future development of 3d metal-catalyzed PRC.

Original languageEnglish
Article numbere202405780
Number of pages13
JournalAngewandte Chemie - International Edition
Volume63
Issue number28
Early online date1 May 2024
DOIs
Publication statusPublished - 8 Jul 2024

Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article. All optimized structures are provided as xyz files in a separate zip-Archive, available free of charge at https://doi.org/10.5281/zenodo.10528904.

Keywords

  • arylation
  • cobalt
  • electron-transfer
  • photoredox catalysis
  • quantum chemistry

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry

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