Amides as modifiable directing groups in electrophilic borylation

Saqib A. Iqbal, Marina Uzelac, Ismat Nawaz, Zhongxing Wang, T. Harri Jones, Kang Yuan, Clement R.P. Millet, Gary S. Nichol, Ghayoor Abbas Chotana, Michael J. Ingleson

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5 Citations (SciVal)

Abstract

Amide directed C-H borylation using ≥two equiv. of BBr3 forms borenium cations containing a R2N(R′)C 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 O→B(Ar)Br unit which has significant Lewis acidity at the carbonyl carbon. This enables reduction of the amide unit to an amine using hydrosilanes. This approach can be applied sequentially in a one-pot electrophilic borylation-reduction process, which for phenyl-acetylamides generates ortho borylated compounds that can be directly oxidised to the 2-(2-aminoethyl)-phenol. Other substrates amenable to the C-H borylation-reduction sequence include mono and diamino-arenes and carbazoles. This represents a simple method to make borylated molecules that would be convoluted to access otherwise (e.g. N-octyl-1-BPin-carbazole). Substituent variation is tolerated at boron as well as in the amide unit, with diarylborenium cations also amenable to reduction. This enables a double C-H borylation-reduction-hydrolysis sequence to access B,N-polycyclic aromatic hydrocarbons (PAHs), including an example where both the boron and nitrogen centres contain functionalisable handles (N-H and B-OH). This method is therefore a useful addition to the metal-free borylation toolbox for accessing useful intermediates (ArylBPin) and novel B,N-PAHs.

Original languageEnglish
JournalChemical Science
DOIs
Publication statusPublished - 15 Mar 2023

Bibliographical note

Funding Information:
This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 769599). We acknowledge SIRCAMS at University of Edinburgh for performing mass spectrometry. IN and GAC acknowledge the Higher Education Commission (HEC) of Pakistan for providing financial support through IRSIP program. IN is also thankful to University of Edinburgh for providing research facilities.

Data availability
The data supporting this article has been uploaded as part of the ESI.†

ASJC Scopus subject areas

  • General Chemistry

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