Polystyrene-Bound Tetrafluorophenylbis(triflyl)methane as an Organic-Solvent-Swellable and Strong Brønsted Acid Catalyst

Abstract

Perfluororesinsulfonic acids such as Nafion are highly acidic solid catalysts, and they are superior to conventional resinsulfonic acids such as Dowex-50, Amberlite IR-112, and Permutit-Q with regard to catalytic activity, thermal stability, and chemical resistance. [1, 2] However, like inorganic solid acids such as zeolites, they are not effectively swollen by most aprotic organic solvents. [3] A resin-bound superacidic Brùnsted acid that is effectively swollen by such solvents may offer several advantages over Nafion, including a broader range of applications, improved yields, improved selectivity, and milder reaction conditions.The trifluoromethanesulfonyl (triflyl, Tf) group is one of the strongest neutral electron-withdrawing groups. [4] In particular, it greatly increases the acidity of a-hydrogen atoms. [5±7] For example, phenylbis(triflyl)methane (1, pK a 7.83 in MeCN) [6] is a strong nonoxidizing acid. The steric and electronic effects of the aromatic ring in arylbis(triflyl)methanes are expected to greatly influence their Brùnsted acidity and their catalytic activity and selectivity for organic reactions. We report here on concise syntheses of the new strong organic Brùnsted acids pentafluorophenylbis(triflyl)methane (2) and polystyrene-bound tetrafluorophenylbis(triflyl)methane (3) and their catalytic applications in organic synthesis.

Trimethylsilyl Pentafluorophenylbis(trifluoromethanesulfonyl)methide as a Super Lewis Acid Catalyst for the Condensation of Trimethylhydroquinone with Isophytol

“…The use of 1 limited the yield of byproducts (two diastereomers of dihydrobenzofuran 5 ) to less than 2 %. In addition, we demonstrate that the reusable super Brønsted acids polystyrene‐bound 2,3,5,6‐tetrafluorophenylbis(trifluoromethanesulfonyl)methane ( 6 )6a, b and 4‐(1 H ,1 H ‐perfluorotetradecanoxy)‐2,3,5,6‐tetrafluorophenylbis(trifluoromethanesulfonyl)methane ( 7 ),6c and their trimethylsilyl derivatives are also effective for the regioselective synthesis of 4 . …”

Atomic hydrogen cleaning of In0.53Ga0.47As studied using synchrotron radiation photoelectron spectroscopy

“…Among these attempts, we found that carbon acids that contain a Tf 2 CH functionality work as better promoters for this transformation. For instance, the use of Tf 2 CHC 6 F 5 5a or Tf 2 CHCH 2 CHTf 2 12 brought about a slight improvement of the product yield (Table 1, entries 5 and 6).…”

Enolizable Carbonyls and N,O‐Acetals: A Rational Approach for Room‐Temperature Lewis Superacid‐Catalyzed Direct α‐Amidoalkylation of Ketones and Aldehydes

“…In accordance with our previous observation on relative transformations with silicon‐based nucleophiles, tin(IV) triflimidate appeared by far superior to a set of triflate and triflimidate salts. Interestingly, use of 5 and 2 mol %, respectively, of the Brønsted superacids Tf 2 NH and C 6 F 5 CH(Tf) 2 gave promising conversions, but Sn(NTf 2 ) 4 displayed substantially better catalytic efficiency, reliably furnishing approximately 70 % conversion into the desired compound 4 aa (Table ).…”