Ni-Catalyzed Electrochemical C(sp2)−C(sp3) Cross-Coupling Reactions

25 August 2020, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Nickel (Ni) catalyzed carbon-carbon (C−C) cross-coupling has been considerably developed in last decades and has demonstrated unique reactivities compared to palladium. However, existing Ni catalyzed cross-coupling reactions, despite success in organic synthesis, are still subject to the use of air-sensitive nucleophiles (i.e. Grignard and organozinc reagents), or catalysts (i.e. Ni0 pre-catalysts), significantly limiting their academic and industrial adoption. Herein, we report that, through electrochemical voltammetry screening and optimization, the redox neutral C(sp2)‒C(sp3) cross-coupling can be accomplished in an undivided cell configuration using bench-stable aryl halide or β-bromostyrene (electrophiles) and benzylic trifluoroborate (nucleophiles) reactants, non-precious, bench stable catalysts consisting of NiCl2•glyme pre-catalyst and polypyridine ligands under ambient conditions. The broad reaction scope and good yields of the Ni-catalyzed electrochemical coupling reaction were confirmed by 48 examples of aryl/β-styrenyl chloride/bromide and benzylic trifluoroborates. Its potential applications were demonstrated by late-stage functionalization of pharmaceuticals and natural amino acid modification. Furthermore, this electrochemical C−C cross-coupling reaction was demonstrated at gram-scale in a flow-cell electrolyzer for practical industrial adoption. Finally, an array of chemical and electrochemical studies mechanistically indicates that electrochemical C−C cross-coupling reaction proceeds through an unconventional radical trans-metalation mechanism.

Keywords

electrosynthesis
Ni catalysis
cross coupling
flow cell synthesis
post-stage functionalization
organic halide
organic borate

Supplementary materials

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200824-NI Coupling-SI-updated
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200824-Ni Coupling-Main-updated
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200824-NI Coupling-SI-updated
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