Catalysis

Photochemistry

Literature

Palladium

Alkyl

Inorganic chemistry

Combinatorial chemistry

Organic chemistry

Photoredox catalysis

Nucleophile

Chemistry

Aryl

Dual (grammatical number)

Nickel

Photocatalysis

Oxidative addition

Halide

Nature Catalysis

Dual photoredox/nickel-catalysed C–N cross-couplings suffer from low yields for electron-rich aryl halides. The formation of catalytically inactive nickel-black is responsible for this limitation and causes severe reproducibility issues. Here, we demonstrate that catalyst deactivation can be avoided by using a carbon nitride photocatalyst. The broad absorption of the heterogeneous photocatalyst enables wavelength-dependent control of the rate of reductive elimination to prevent nickel-black formation during the coupling of cyclic, secondary amines and aryl halides. A second approach, which is applicable to a broader set of electron-rich aryl halides, is to run the reactions at high concentrations to increase the rate of oxidative addition. Less nucleophilic, primary amines can be coupled with electron-rich aryl halides by stabilizing low-valent nickel intermediates with a suitable additive. The developed protocols enable reproducible, selective C–N cross-couplings of electron-rich aryl bromides and can also be applied for electron-poor aryl chlorides. Dual nickel/photoredox catalysis is a promising alternative for palladium-catalysed cross-couplings, but suffers from limitations. Now, the substrate scope and reproducibility of this method are improved by avoiding catalyst deactivation and strategies to achieve the latter are reported.

Overcoming limitations in dual photoredox/nickel-catalysed C–N cross-couplings due to catalyst deactivation