On the reactivity and stability of electrogenerated N-heterocyclic carbene in parent 1-butyl-3-methyl-1H-imidazolium tetrafluoroborate: Formation and use of N-heterocyclic carbene-CO2 adduct as latent catalyst

A simple electrolysis (under galvanostatic conditions) of the room temperature ionic liquid 1-butyl-3-methyl-1H-imidazolium tetrafluoroborate, BMIm-BF4, yields, after bubbling CO2 into the catholyte, the adduct NHC-CO2. The considerable stability of this NHC-CO2 adduct, at room temperature, in the parent ionic liquid as solvent, has been compared with the one of free NHC in the same BMIm-BF4. The BMIm-BF4 solution containing NHC-CO2 adduct, suitably triggered (US irradiation or 120 degrees C), is able to release free NHC. The NHC-CO2 adduct usefulness has been demonstrated using it as efficient latent catalyst, in BMIm-BF4 as solvent, in the benzoin condensation and in the oxidative esterification of cinnamaldehyde with benzyl alcohol. (C) 2013 Elsevier Ltd. All rights reserved.