Esterification of carboxylic acids with alkyl halides using imidazolium based dicationic ionic liquids containing bis-trifluoromethane sulfonimide anions at room temperature

Abstract

Task-specific room temperature ionic liquids (RTILs) composed of symmetrical N-methylimidazolium rings linked with a short oligo (ethylene glycol) chain (cationic part) and bis-trifluoromethane sulfonimide (NTf 2 , anionic part) were successfully synthesized, and their physicochemical properties were determined by various modern analytical techniques. The catalytic activity of the synthesized RTILs was evaluated in the esterification reaction of acids with alkyl halides in solvent-free conditions at room temperature. From the screening test, all the synthesized RTILs showed a high yield with significant selectivity for respective esters in a very short reaction time. Especially, 0.1 equimolar of RTIL-1 ([tetraEG(mim) 2 ][NTf 2 ] 2 ) was found to be, the most efficient and reusable catalyst for this reaction. As a result, 100% conversion and up to a 94% yield of the respective ester product was obtained in a 30 min reaction time. This might be due to their synergetic effect of Lewis acidity, wide liquid range, and high miscibility compared to the other homogeneous and heterogeneous catalysts. Beside this, RTIL was easily separated from the reaction mixture and reused several times without any significant loss of catalytic activity and structural property.The present dicationic ionic liquids (ILs) under a solvent-free catalytic system were found to be kinetically fast, naturally benign, and achieved good yields for esterification of carboxylic acids with alkyl halides.

Probing the electronic structure of ether functionalised ionic liquids using X-ray photoelectron spectroscopy

“…21 Improved catalytic performance and reduced viscosities, when compared to alkyl substituted analogues, is also noted. 14,[22][23][24][25][26][27] Ether and PEG substituted systems now find application as alternative solvents or performance molecules across multiple aspects of science, technology and engineering, [28][29][30][31][32][33] including, for example, as catalyst for the synthesis of butyl acetate and subsequent esterification of carboxylic acid, 22,23 for selective CO 2 capture, 34 and as anti-wear additives to improve tribological performance. 32,33 Early XPS studies of PEG-functionalized systems have largely focused upon the orientation of surface structure of imidazolium-based systems, 7,10,35 and were completed out using nonmonochromatic X-ray sources which sometimes suffer from reduced resolution of primary XP photoemission envelopes.…”

A facile and sustainable protocol to the preparation of aryl iodides using stable arenediazonium bis(trifluoromethylsulfonyl)imide salts via the telescopic process

“…Over the past decade, bis(trifluoromethane)sulfonamide (TFSI‐H) and its salts have attracted much interest for their use as catalyst during the ring‐opening polymerization of octamethylcyclotetrasiloxane in the presence of hexamethyldisiloxane, the synthesis of various non‐reducing disaccharides via ketopyranosylation of 2,3,4,6‐tetra‐O‐benzyl‐1‐C‐methyl‐D‐hexopyranoses, esterification carboxylic acid with alkyl halides, reactant for preparing the N ‐fluoro‐bis[(trifluoromethyl)sulfonyl]imide (TFSI‐F) as an efficient fluorinating agent, and as a component of solid polymer electrolytes . Synthesis, properties, and reactions of TFSI‐H were previously studied .…”

Recent Advances in the Synthesis of Carboxylic Acid Esters

“…Since then, various reactions have been reported in these fields. Recent examples of this chemistry utilize the combination of bases (such as Huning's base, Et 3 N and KF) and various ionic liquids (such as imidazolium salts and phosphonium salts), summarized in Figure 1 [82][83][84][85][86][87][88][89][90]. The countercations of carboxylate ions are bulky cations such as imidazolium salts and phosphonium salts, which seem to increase the reactivity of the carboxylate ions toward electrophiles.…”