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Download fileElectrochemical Reductive N‑Methylation with CO2 Enabled by a Molecular Catalyst
journal contribution
posted on 2021-11-16, 19:04 authored by Conor
L. Rooney, Yueshen Wu, Zixu Tao, Hailiang WangThe development of benign methylation
reactions utilizing CO2 as a one-carbon building block
would enable a more sustainable
chemical industry. Electrochemical CO2 reduction has been
extensively studied, but its application for reductive methylation
reactions remains out of the scope of current electrocatalysis. Here,
we report the first electrochemical reductive N-methylation reaction
with CO2 and demonstrate its compatibility with amines,
hydroxylamines, and hydrazine. Catalyzed by cobalt phthalocyanine
molecules supported on carbon nanotubes, the N-methylation reaction
proceeds in aqueous media via the chemical condensation of an electrophilic
carbon intermediate, proposed to be adsorbed or near-electrode formaldehyde
formed from the four-electron reduction of CO2, with nucleophilic
nitrogenous reactants and subsequent reduction. By comparing various
amines, we discover that the nucleophilicity of the amine reactant
is a descriptor for the C–N coupling efficacy. We extend the
scope of the reaction to be compatible with cheap and abundant nitro-compounds
by developing a cascade reduction process in which CO2 and
nitro-compounds are reduced concurrently to yield N-methylamines with high monomethylation selectivity via the overall
transfer of 12 electrons and 12 protons.
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nucleophilic nitrogenous reactantselectrode formaldehyde formedaqueous media viasustainable chemical industryelectrophilic carbon intermediatecomparing various aminescascade reduction processmethylation reaction proceeds2 </ submethylation reactionchemical condensationcarbon nanotubessubsequent reductionreduced concurrentlyoverall transfern </molecular catalystextensively studiedelectron reductioncurrent electrocatalysisamine reactant>- methylamines12 protons12 electrons