Issue 14, 2023

Amides as modifiable directing groups in electrophilic borylation

Abstract

Amide directed C–H borylation using ≥two equiv. of BBr3 forms borenium cations containing a R2N(R′)C[double bond, length as m-dash]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.

Graphical abstract: Amides as modifiable directing groups in electrophilic borylation

Supplementary files

Article information

Article type
Edge Article
Submitted
24 Nov 2022
Accepted
14 Mar 2023
First published
15 Mar 2023
This article is Open Access

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

Chem. Sci., 2023,14, 3865-3872

Amides as modifiable directing groups in electrophilic borylation

S. A. Iqbal, M. Uzelac, I. Nawaz, Z. Wang, T. H. Jones, K. Yuan, C. R. P. Millet, G. S. Nichol, G. A. Chotana and M. J. Ingleson, Chem. Sci., 2023, 14, 3865 DOI: 10.1039/D2SC06483A

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