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Proton‐Exchange Equilibrium between Bases and [BMIm][BF 4 ]: An Electrochemical Procedure to Evaluate the Presence of Carbenes for Synthetic Applications
Author(s) -
Chiarotto Isabella,
Feroci Marta,
Forte Gianpiero,
Orsini Monica,
Inesi Achille
Publication year - 2014
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201402134
Subject(s) - ionic liquid , triethylamine , electrochemistry , tetrafluoroborate , chemistry , base (topology) , carbene , solvent , yield (engineering) , catalysis , proton , medicinal chemistry , inorganic chemistry , organic chemistry , electrode , materials science , mathematical analysis , mathematics , metallurgy , physics , quantum mechanics
The ability of a base to yield an N‐heterocyclic carbene (NHC) in a base–ionic‐liquid solution is investigated by using an electrochemical procedure. Accordingly, the equilibrium of proton exchange between different bases (1,5‐diazabicyclo[5.4.0]undec‐5‐ene, 1,1,2,3,3‐pentaisopropylguanidine, Cs 2 CO 3 , 2,4,6‐trimethylpyridine, and triethylamine) and the 1‐butyl‐3‐methylimidazolium (BMIm + ) cation was studied with the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm][BF 4 ]) as a solvent. The concentration of NHC, in the different base–[BMIm][BF 4 ] systems, is derivable from the anodic peak current (related to the oxidation of NHC) of the voltammograms recorded in base–[BMIm][BF 4 ] solutions. The electrochemical procedure allows utilisation of base–[BMIm][BF 4 ] solutions as a media that is capable of inducing NHC‐catalysed syntheses. The NHC‐catalysed oxidation of aldehydes to esters is selected as a model reaction. The results of the syntheses are in accordance with electrochemical forecasts.