By leveraging a nickel oxyhydroxide (NiOOH) catalyst, the team led by Dr Amanda Garcia achieved selective oxidation of benzyl alcohol to form benzaldehyde, a key intermediate, followed by its conversion to benzyl-tert-butylamine via reductive amination. The researchers were able to demonstrate impressive conversion efficiencies: up to 90% faradaic efficiency for benzaldehyde formation and an overall 35% efficiency for the final product. Their process avoids the use of high-pressure systems, noble metals, and hazardous chemicals.

The study highlights the role of catalyst design and operating conditions in enhancing efficiency and selectivity. For example, the thickness of the nickel catalyst layer directly influenced product selectivity, while the choice of solvents and pH conditions helped prevent overoxidation and unwanted side reactions.

This research opens a pathway for scalable, environmentally friendly amine production using renewable electricity, aligning with global goals for green chemistry and sustainable industrial practices. Future improvements in catalyst stability and system integration could further enhance the commercial viability of this innovative method.

Abstract, as published with the paper

The development of sustainable synthetic methods for converting alcohols to amines is of great interest due to their widespread use in pharmaceuticals and fine chemicals. In this work, we present an electrochemical approach by using green electrons for the selective oxidation of benzyl alcohol to benzaldehyde using a NiOOH catalyst, followed by its reductive amination to form benzyl-tert-butylamine. The number of Ni monolayer equivalents on the catalyst was found to significantly influence selectivity, with 2 monolayers achieving up to 90% faradaic efficiency (FE) for benzaldehyde in NaOH, while 10 monolayers performed best in a tert-butylamine solution (pH 11), yielding 100% FE for benzaldehyde. Reductive amination of benzaldehyde was optimized on Ag and Pb electrodes, with Ag achieving 39% FE towards the amine product, though hydrogen evolution remained a competing reaction. In situ FTIR spectroscopy confirmed the formation of benzaldehyde and its corresponding imine intermediate during oxidation, while reduction spectra supported the formation of the amine product. These results demonstrate the potential of paired electrolysis for alcohol-to-amine conversion, achieving an overall 35% FE for the synthesis of benzyl-tert-butylamine. This work paves the way for more efficient and sustainable electrochemical routes to amine synthesis.

Paper details

P. J. L. Broersen, V. Paschalidou and A. C. Garcia: Electrosynthesis of benzyl-tert-butylamine via nickel-catalyzed oxidation of benzyl alcohol. Green Chem., 2025, Advance article. DOI: 10.1039/D4GC05171H

See also

Amsterdam Centre for Electrochemistry (Amcel)