Synthesis and applications of superacids. 1,1,2,2-Tetrafluoroethanesulfonic acid, supported on silica

Abstract

In this paper we focus on the synthesis and use of superacids, in particular 1,1,2,2tetrafluoroethanesulfonic acid (TFESA), and describe how these can be optimized for reactions of key industrial importance. One area of considerable interest is the field of superacid catalysis and, specifically, the development of safer and more cost-effective acid catalysts. We report a new simplified route for preparation of these acids, making these more readily available and opening up a large number of opportunities. Partially fluorinated superacids offer several advantages over the acids commonly used in catalysis (sulfuric, hydrofluoric acid and aluminium chloride): lower loadings, lower reaction temperatures (leading to increased selectivity), fewer by-products, shorter reaction times and higher throughput. TFESA and its longer chain analogs are much less volatile than triflic acid (CF 3 SO 3 H). We tested these superacids in several processes (aromatic alkylation, acylation of arenes, isomerization, oligomerization and the Fries rearrangement). These materials are excellent acid catalysts, comparable to triflic acid, and yet easier to handle. We have also prepared supported versions of these catalysts and introduced the ability to recycle.

Cellobiose hydrolysis using acid-functionalized nanoparticles

“…PFS nanoparticles lost their acid groups to a larger extent than AS nanoparticles did. Fluoroalkyl-sulfonic acids have superacidic character but they are also water sensitive [17,42,43,51]. The anchorage of PFS acids on SiMNPs was not enough to improve its stability.…”

“…Nanoporous solids with acid sites have shown high catalytic activity in gas and liquid phase reactions [17]. Efficient catalysis of cellulose hydrolysis was observed using amorphous carbon with surface sulfonic acid, carboxylic acid, and hydroxyl groups [18].…”

Trifluoromethanesulfonic Acid as Acylation Catalyst: Special Feature for C- and/or O-Acylation Reactions

“…Therefore, it is categorized as a superacid and expected to be an effective catalyst for Friedel-Crafts C-acylation. A comparative study using sulfuric acid, TfOH, and three other perfluorinated sulfonic acids synthesized by Harmer et al [15] in the acylation of anisole 1 (Figure 2a) proved this expectation. Moreover, the Fries rearrangement of phenyl acetate 2 ( Figure 2b) also shows high efficiency of TfOH utilization as a catalyst as it is 100 times stronger than sulfuric acid [13,16] and is a commercially available reagent which can be readily used for these reactions.…”

Superacid Systems

“…Harmer et al 29 have applied the sol-gel technique to prepare 1,1,2,2-tetrafluoroethanesulfonic acid supported on silica, which proved to be an excellent catalyst for several processes such as alkylation and acylation of aromatics, isomerization, oligomerization, and Fries rearrangement. This material has activity similar to that of triflic acid but is much easier to handle.…”

“…Harmer et al 28,29 have reported the synthesis of 1,1,2,2-tetrafluoroethanesulfonic acid, CF 2 HCF 2 SO 3 H, and 1,1,2,3,3,3-hexafluoropropanesulfonic acid, CF 3 CFHCF 2 -SO 3 H, by the addition of sulfite to fluorinated double bonds [Eq. (2.12)].…”