Electrogenerated N-Heterocyclic Olefins: Stability and Catalytic Ability

N-Heterocyclic olefin (NHO) can be generated by simple cathodic reduction of BDMImBF-DMF solution or neat BDMImBF (BDMImBF=1-butyl-2,3-dimethyl-1H-imidazolium tetrafluoroborate; DMF=dimethylformamide). In the latter case, the use of any organic solvent and chemical base is avoided. To prove the presence of NHO, its adduct with benzaldehyde was isolated. The electrochemical behavior of NHO is very similar to that of the corresponding N-heterocyclic carbene (NHC, from 1-butyl-3-methyl-1H-imidazolium tetrafluoroborate), showing that it is electroactive at the anode, and this peculiarity can be exploited to verify its presence in a solution. The main difference between NHO and NHC is in the nucleophilic site (exocyclic for NHO, endocyclic for NHC). Electrogenerated NHO stability (evaluated by cyclic voltammetry) and its catalytic ability (evaluated in the transesterification reaction) were compared with those of electrogenerated NHC.