Internal redox amidation of α,β-unsaturated aldehydes in ionic liquids. The electrochemical route

A simple, N-heterocyclic carbene (NHC) activated synthesis of amides has been performed via electrolysis, carried out under galvanostatic control, of an ionic liquid (Bmim-BF4) followed by addition to the catholyte of an α,β-unsaturated aldehyde and amine. Amides have been isolated, in good to elevated yields, in the absence of any base, co-catalyst and organic solvent. The selectivity of amidation, versus the formation of imine as by-product, has been related to the molar ratio electrogenerated NHC/aldehyde. The results, obtained using ionic liquids and electrochemical procedures, have been compared with those obtained using organic solvents and classical procedures.

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► NHC was easily obtained by galvanostatic reduction of Bmim-BF4.
► Electrogenerated NHC catalyzed the internal redox reaction of unsaturated aldehydes.
► Amidation has been obtained avoiding the formation of imine.