Chemistry of Fluorinated Carbon Acids: Synthesis, Physicochemical Properties, and Catalysis

Abstract

The bis[(trifluoromethyl)sulfonyl]methyl (Tf 2 CH; Tf SO 2 CF 3 ) group is known to be one of the strongest carbon acid functionalities. The acidity of such carbon acids in the gas phase is stronger than that of sulfuric acid. Our recent investigations have demonstrated that this type of carbon acids work as novel acid catalysts. In this paper, recent achievements in carbon acid chemistry by our research group, including synthesis, physicochemical properties, and catalysis, are summarized.

2‐(Pyridinium‐1‐yl)‐1,1‐bis(perfluoroalkylsulfonyl)ethan‐1‐ide: A Practical Reagent for Synthesis of Strongly Acidic 1,1‐Bis(perfluoroalkylsulfonyl)alkanes

“…The reaction of 4f with 2.0 equiv of p-cresol in acetonitrile went to completion within only 10 min at room temperature. 1 HNMR analysiso ft he crude material showed clean formation of the desired carbon acid 8a and 2-fluoropyridine (7). This resulte videncest hat 4f smoothly produces Tf 2 C=CH 2 (2a).…”

“…2017, 23,8203 -8211 www.chemeurj.org virtually nonbasic compound. In the synthesis of strongly acidic carbon acids and their derivatives, the fact that 2-fluoropyridine (7)c an be easily removed by evaporation playeda n important role. Secondly,n oa cidic speciesw ere present in this equilibrium mixture.…”

“…This structural featurei sa na dvantage for the development of novels trong acids. For instance, in several synthetic reactions, including the Mukaiyama aldol and relatedr eactions, higher catalytic performanceo fT f 2 CHR over conventional TfOH and Tf 2 NH has been reported by us, [7,8] Yamamoto, Ishiharae tal., [9] and List et al [10] However,f lexible molecular design of carbonacid catalysts is still difficult owning to alack of general and effectives ynthetic methods. [11] For example, a-alkylation reactions of commercially availableT f 2 CH 2 (1a)w ith alkyl halides gave unsatisfactory results owning to the remarkably low nucleophilicity of the bis(triflyl)methanidei on.…”

HFIP‐Mediated Desulfinative Friedel–Crafts Cyclobutenylation Reaction

“…In the original protocol by Alcaide and Almendros, [12] zwitterionic reagent 4 was adopted as a source for Tf 2 C=CH 2 . On the other hand, here we found that the desired molecular transformation smoothly proceeded by mixing Tf 2 CH 2 3 , paraformaldehyde, and diphenylacetylene in 1,2‐dichloroethane (DCE) under gently heating conditions to give the cyclobutene product 5 a in an excellent yield [18] . According to this precedure, we prepared several gem ‐bis(triflyl)cyclobutenes needed in this work ( vide infra ).…”

Development of Stable Carbanionic Substituents

“…[5] The author has studied synthesis, acidity evaluation and catalytic usage of such strong carbon acids. [6] The development of new strong acids leads to stable anionic species (Figure 1). In the first report by Haszeldine and co-workers, [3b] it was mentioned that bis(triflyl)methane 1 a produced the corresponding sodium and silver salts by neutralisation.…”