Merging Electrolysis and Nickel Catalysis in Redox Neutral Cross-Coupling Reactions: Experiment and Computation for Electrochemically Induced C–P and C–Se Bonds Formation

Abstract

We have achieved a nickel-catalyzed cross-coupling reaction via concerted paired electrolysis under mild reaction conditions. In this electrochemical transformation, the anodic oxidation of Ni II to Ni III and cathodic reduction of Ni I to Ni 0 occurred simultaneously, resulting in an economical and sustainable cross-coupling protocol. Moreover, we performed mechanistic investigations, achieved by experiments and density functional theory (DFT) calculations for different C-heteroatom bond formations to reveal the catalytic cycle in more detail.

Redox-Neutral Cross-Coupling Amination with Weak N-Nucleophiles: Arylation of Anilines, Sulfonamides, Sulfoximines, Carbamates, and Imines via Nickelaelectrocatalysis

“…Of note, the current efficiency at 40 min was 154%, which suggests the role of electricity is to suppress the comproportionation of the unstable Ni I and Ni III intermediates ( Figure 4 b). 61 Furthermore, the reaction of 4-bromobenzonitrile with TsNH 2 using Ni(cod) 2 without electricity proceeded with very low efficiency, indicating the difficulty of reductive elimination at the Ni II intermediate ( Figure 4 c), which is further supported by DFT calculations. The calculations show that the reductive elimination energy barrier from Ni II and Ni III complexes in amination reactions are 26.1 and 6.7 kcal/mol, while those for the sulfonamidation reaction are 34.2 and 13.2 kcal/mol, respectively ( Figure 4 d).…”

Harnessing Radical Chemistry via Electrochemical Transition Metal Catalysis

“…Mechanistically, a P-centered radical was proposed to interact with the Ni(II) complex to generate Ni(III) species en route to product formation via reductive elimination ( Scheme 4 ). However, a similar reaction system developed by the Rueping group suggested the generation of phosphorus radical was not involved in the reaction ( Zhu et al., 2020 ).

Scheme 4 Electrochemical Ni-Catalyzed C-P Bond Formation

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Electrocatalytic redox neutral [3 + 2] annulation of N-cyclopropylanilines and alkenes

“…One involves the product radical cation or anion being stable enough to migrate to the cathode or anode so that a SET reduction or oxidation occurs to yield the nal neutral product. [77][78][79][80] The other requires the product radical cation or anion to undergo a SET oxidation or reduction with the starting material in a chain mechanism. The former is more arduous to meet as a tandem oxidation/ reduction has to occur on a macroscopically separated anode and cathode.…”