Issue 35, 2022

Iron-catalysed alkene and heteroarene H/D exchange by reversible protonation of iron-hydride intermediates

Abstract

C–H functionalisation reactions offer a sustainable method for molecular construction and diversification. These reactions however remain dominated by precious metal catalysis. While significant interest in iron-catalysed C–H activation reactions has emerged, the isolation, characterisation and mechanistic understanding of these processes remain lacking. Herein the iron-catalysed C(sp2)–H bond hydrogen/deuterium exchange reaction using CD3OD is reported for both heterocycles and, for the first time, alkenes (38 examples). Isolation and characterisation, including by single-crystal X-ray diffraction, of the key iron-aryl and iron-alkenyl C–H metallation intermediates provided evidence for a reversible protonation of the active iron hydride catalyst. Good chemoselectivity was observed for both substrate classes. The developed procedure is orthogonal to previous iron-catalysed H/D exchange methods which used C6D6, D2, or D2O as the deuterium source, and uses only bench-stable reagents, including the iron(II) pre-catalyst. Further, a new mechanism of iron-hydride formation is reported in which β-hydride elimination from an alcohol generates the iron hydride. The ability to produce, isolate and characterise the organometallic products arising from C–H activation presents a basis for future discovery and development.

Graphical abstract: Iron-catalysed alkene and heteroarene H/D exchange by reversible protonation of iron-hydride intermediates

Supplementary files

Article information

Article type
Edge Article
Submitted
07 7 2022
Accepted
08 8 2022
First published
11 8 2022
This article is Open Access

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

Chem. Sci., 2022,13, 10291-10298

Iron-catalysed alkene and heteroarene H/D exchange by reversible protonation of iron-hydride intermediates

L. Britton, J. H. Docherty, J. Sklyaruk, J. Cooney, G. S. Nichol, A. P. Dominey and S. P. Thomas, Chem. Sci., 2022, 13, 10291 DOI: 10.1039/D2SC03802A

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