Issue 23, 2021

Zinc catalysed electrophilic C–H borylation of heteroarenes

Abstract

Cationic zinc Lewis acids catalyse the C–H borylation of heteroarenes using pinacol borane (HBPin) or catechol borane (HBCat). An electrophile derived from [IDippZnEt][B(C6F5)4] (IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) combined with N,N-dimethyl-p-toluidine (DMT) proved the most active in terms of C–H borylation scope and yield. Using this combination weakly activated heteroarenes, such as thiophene, were amenable to catalytic C–H borylation using HBCat. Competition reactions show these IDipp–zinc cations are highly oxophilic but less hydridophilic (relative to B(C6F5)3), and that borylation proceeds via activation of the hydroborane (and not the heteroarene) by a zinc electrophile. Based on DFT calculations this activation is proposed to proceed by coordination of a hydroborane oxygen to the zinc centre to generate a boron electrophile that effects C–H borylation. Thus, Lewis acid binding to oxygen sites of hydroboranes represents an under-developed route to access reactive borenium-type electrophiles for C–H borylation.

Graphical abstract: Zinc catalysed electrophilic C–H borylation of heteroarenes

Supplementary files

Article information

Article type
Edge Article
Submitted
05 Apr 2021
Accepted
12 May 2021
First published
13 May 2021
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., 2021,12, 8190-8198

Zinc catalysed electrophilic C–H borylation of heteroarenes

M. E. Grundy, K. Yuan, G. S. Nichol and M. J. Ingleson, Chem. Sci., 2021, 12, 8190 DOI: 10.1039/D1SC01883C

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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