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A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis
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Reductively Induced Aryl Transmetalation: An Alternative Catalytically Relevant Ni-Catalyzed Biaryl Coupling
Antonio Romero-Arenas1,2, Mihai V Popescu3, McKenna K Goetz1
1Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.
Journal of the American Chemical Society
|June 10, 2025
Summary
This study reveals a new Ni-catalyzed cross-electrophile coupling pathway involving reductively induced transmetalation between Ni(I) and Ni(II) species. This mechanism explains biaryl formation and offers new strategies for nickel-catalyzed reactions.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Synthetic Organic Chemistry
Background:
- Nickel-catalyzed cross-electrophile coupling (XEC) reactions are vital for C-C bond formation.
- Existing XEC mechanisms for biaryl synthesis involve various pathways for Ni(Ar)2 intermediate formation.
- A deeper mechanistic understanding is crucial for optimizing these important synthetic transformations.
Purpose of the Study:
- To investigate and provide evidence for a previously unrecognized mechanism in Ni-catalyzed XEC reactions.
- To elucidate the role of reductively induced transmetalation in the formation of Ni(Ar)2 intermediates.
- To offer a new mechanistic rationale for previously observed results in biaryl coupling.
Main Methods:
- Electrochemical and chemical reduction of a Ni(II) complex to generate a Ni(I) species.
- Characterization of reaction products, including Ni(II) diaryl complexes.
- Kinetic studies and computational analysis to compare proposed transmetalation pathways.
Main Results:
- Evidence for a Ni(I)-to-Ni(II) transmetalation pathway, forming Ni(II)(Ar)2 from Ni(I)(Ar) and Ni(II)(Ar)X.
- This Ni(I)-mediated pathway is significantly more favorable than Ni(II)-to-Ni(II) transmetalation.
- Autocatalytic behavior in biaryl formation is observed, consistent with the proposed Ni(I)-to-Ni(II) transmetalation mechanism.
Conclusions:
- A novel reductive transmetalation pathway involving Ni(I) species is identified in Ni-catalyzed biaryl coupling.
- This mechanism provides a new explanation for the formation of key Ni(II) diaryl intermediates.
- The findings offer alternative mechanistic insights for the development of improved Ni-catalyzed cross-coupling reactions.
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