Quinone-mediated hydrogen anode for non-aqueous reductive electrosynthesis.

Area of Science:

• Green Chemistry
• Electrochemistry
• Organic Synthesis

Background:

• Electrochemical synthesis offers sustainable routes to industrial chemicals.
• Electrosynthetic reductions typically require external electron sources, often relying on sacrificial anodes.
• Anodic water oxidation is appealing but limited by anhydrous reaction condition requirements, highlighting the need for alternative reductant sources like H2.

Purpose of the Study:

• To develop a sustainable, mediated hydrogen anode for electrosynthetic reductions under non-aqueous conditions.
• To enable indirect electrochemical oxidation of H2 using a quinone mediator.
• To apply this technology to challenging reactions like nickel-catalyzed cross-electrophile coupling (XEC).

Main Methods:

• A mediated H2 anode was developed by coupling thermal catalytic hydrogenation of an anthraquinone mediator with electrochemical oxidation of the anthrahydroquinone.
• The mediated anode was utilized to support nickel-catalyzed cross-electrophile coupling (XEC) reactions.
• The method was validated in small-scale batch reactions and scaled up in a recirculating flow reactor.

Main Results:

• The quinone-mediated H2 anode successfully supported nickel-catalyzed XEC reactions.
• Hectogram-scale synthesis of a pharmaceutical intermediate was achieved using a recirculating flow reactor.
• The developed technology provides a general strategy for H2-driven electrosynthetic reductions.

Conclusions:

• Mediated H2 anode technology offers a sustainable alternative to sacrificial anodes for electrosynthetic reductions.
• This approach facilitates greener chemical manufacturing, particularly in the pharmaceutical industry.
• The system is adaptable for both small-scale validation and large-scale synthesis.