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

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 22; no. 3; pp. 86 - 869
• Main Authors: Appiagyei, Benjamin, Bhatia, Souful, Keeney, Gabriela L, Dolmetsch, Troy, Jackson, James E
• Format: Journal Article
• Published: 10.02.2020
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/c9gc03747k

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. Aqueous electrocatalytic alkylation of amines with alcohol; water is the only byproduct.