Aminoborate-Catalyzed Reductive Counterreactions for Oxidative Electrosynthetic Transformations

Area of Science:

• Electrochemistry
• Organic Synthesis
• Catalysis

Background:

• Proton reduction is crucial for electrooxidative transformations but often slow in organic solvents and requires harsh potentials.
• Existing cathodic counterreactions can limit the scope and efficiency of desired oxidative processes.

Purpose of the Study:

• To develop novel redox mediators for proton reduction that operate at mild potentials.
• To enable challenging oxidative organic transformations using an efficient cathodic process.

Main Methods:

• Investigated aminoborate adducts as redox mediators for proton reduction.
• Applied these mediators to electrooxidative chlorodeborylation and copper-catalyzed Chan-Lam coupling reactions.
• Characterized the electrochemical properties of pyridinium borate adducts.

Main Results:

• Aminoborate adducts, specifically pyridinium borate complexes, efficiently mediate proton reduction at mild potentials (-1.1 V vs Fc/Fc+).
• The developed chlorodeborylation reaction and previously reported Chan-Lam coupling showed high yields.
• These mediators suppressed substrate decomposition and electrode passivation, leading to improved reaction stability.

Conclusions:

• Aminoborate adducts are effective redox mediators for cathodic proton reduction in electrosynthesis.
• The use of these mediators facilitates milder and more efficient oxidative organic transformations.
• This work highlights the importance of designing compatible anodic and cathodic reactions for electrosynthesis.