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Photoexcited Pd(ii) auxiliaries enable light-induced control in C(sp3)–H bond functionalisation

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Abstract

Herein we report the photophysical and photochemical properties of palladacycle complexes derived from 8-aminoquinoline ligands, commonly used auxiliaries in C–H activation. Spectroscopic, electrochemical and computational studies reveal that visible light irradiation induces a mixed LLCT/MLCT charge transfer providing access to synthetically relevant Pd(III)/Pd(IV) redox couples. The Pd(II) complex undergoes photoinduced electron transfer with alkyl halides generating C(sp3)–H halogenation products rather than C–C bond adducts. Online photochemical ESI-MS analysis implicates participation of a mononuclear Pd(III) species which promotes C–X bond formation via a distinct Pd(III)/Pd(IV) pathway. To demonstrate the synthetic utility, we developed a general method for inert C(sp3)–H bond bromination, chlorination and iodination with alkyl halides. This new strategy in auxiliary-directed C–H activation provides predictable and controllable access to distinct reactivity pathways proceeding via Pd(III)/Pd(IV) redox couples induced by visible light irradiation.

Graphical abstract: Photoexcited Pd(ii) auxiliaries enable light-induced control in C(sp3)–H bond functionalisation

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Article information


Submitted
12 Nov 2019
Accepted
21 Jan 2020
First published
23 Jan 2020

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2020, Advance Article
Article type
Edge Article

Photoexcited Pd(II) auxiliaries enable light-induced control in C(sp3)–H bond functionalisation

M. L. Czyz, G. K. Weragoda, T. H. Horngren, T. U. Connell, D. Gomez, R. A. J. O'Hair and A. Polyzos, Chem. Sci., 2020, Advance Article , DOI: 10.1039/C9SC05722F

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