Issue 3, 2020

Electroactivated alkylation of amines with alcohols via both direct and indirect borrowing hydrogen mechanisms

Abstract

A green, efficient N-alkylation of amines with simple alcohols has been achieved in aqueous solution via an electrochemical version of the so-called “borrowing hydrogen methodology”. Catalyzed by Ru on activated carbon cloth (Ru/ACC), the reaction works well with methanol, and with primary and secondary alcohols. Alkylation can be accomplished by either of two different electrocatalytic processes: (1) in an undivided cell, alcohol (present in excess) is oxidized at the Ru/ACC anode; the aldehyde or ketone product condenses with the amine; and the resulting imine is reduced at an ACC cathode, combining with protons released by the oxidation. This process consumes stoichiometric quantities of current. (2) In a membrane-divided cell, the current-activated Ru/ACC cathode effects direct C–H activation of the alcohol; the resulting carbonyl species, either free or still surface-adsorbed, condenses with amine to form imine and is reduced as in (1). These alcohol activation processes can alkylate primary and secondary aliphatic amines, as well as ammonia itself at 25–70 °C and ambient pressure.

Graphical abstract: Electroactivated alkylation of amines with alcohols via both direct and indirect borrowing hydrogen mechanisms

Supplementary files

Article information

Article type
Paper
Submitted
31 Okt 2019
Accepted
24 Dis 2019
First published
03 Jan 2020

Green Chem., 2020,22, 860-869

Author version available

Electroactivated alkylation of amines with alcohols via both direct and indirect borrowing hydrogen mechanisms

B. Appiagyei, S. Bhatia, G. L. Keeney, T. Dolmetsch and J. E. Jackson, Green Chem., 2020, 22, 860 DOI: 10.1039/C9GC03747K

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