[120418-31-7] · C11H12F6N4O7S2 · 1,1´-Carbonylbis(3-methylimidazolium) Bis(trifluoromethanesulfonate) · (MW 490.36)
(versatile coupling reagent for aminoacylations2)
Alternate Name: 1,1-carbonylbis(3-methylimidazolium) bistriflate.
Physical Data: pale white solid mp 78-80 °C; 1H d (CDCl3) 8.86 (s, 2H), 7.44 (m, 2H), 7.16 (m, 2H), 4.00 (s, 6H).
Solubility: sol nitromethane, chloroform; insol ether; reacts with water.
Analysis of Reagent Purity: freshly prepared sample is treated with water: 200 mol % of N-methylimidazolium triflate is produced along with CO2.
Preparative Methods: fresh methyl triflate is added to 1,1-carbonylbisimidazole in nitromethane at 10 °C. Solvent is then removed in vacuo, or the reagent used in situ.2
Handling, Storage, and Precautions: usually prepared under anhydrous conditions and used immediately. Can be stored in dry nitromethane solution or in solid state in absence of moisture. Preparation using aged methyl triflate should be avoided, owing to possible contamination of the coupling reagent with triflic acid.2
When N-Cbz derived amino acids are exposed to a freshly prepared solution of carbonylbis(3-methylimidazolium) triflate in nitromethane, coupling ensues with loss of CO2 to give the derived amide and one equivalent of methylimidazolium triflate (eq 1).2
The acylated species so prepared can be coupled with Of particular note is the fact that sterically hindered alcohols (e.g. menthol) couple in nearly quantitative yield (eq 3).
Graham B. Jones & Robert S. Huber Clemson University, SC, USA
Of particular note is the fact that sterically hindered alcohols (e.g. menthol) couple in nearly quantitative yield (eq 3).
Graham B. Jones & Robert S. Huber
Clemson University, SC, USA