CF3SO3H

Perchloric acid (HCIO4 Ho —13.0), fluorosulfuric acid (HSO3F Ho — 15.1), and trifluoromethanesulfonic acid (CF3SO3H Ho —14.1) are considered to be superacids, as is truly anhydrous hydrogen fluoride. Complexing with Lewis acidic metal fluorides of higher valence, such as antimony, tantalum, or niobium pentafluoride, greatly enhances the acidity of all these acids. 

CF3SO3H, PhSMe, 0-25°. ° In this case O-methyltyrosine was depro-tected without evidence for O C migration, which is often a problem when removing protective groups from tyrosine. 

Isobutylene, CF3SO3H, CH2CI2, —78°, 70-90% yield. These conditions will protect a phenol in the presence of a primary alcohol. 

Sulfobenzyl esters were prepared (cesium salt or dicyclohexylammonium salt, Na03SC6H4CH2Br, DMF, 37-95% yield) from A -protected amino acids. They are cleaved by hydrogenolysis (H2/Pd), or hydrolysis (NaOH, dioxane/water). Treatment with ammonia-or hydrazine results in formation of the amide or hydrazide. The ester is stable to 2 M HBr/AcOH and to CF3SO3H in CF3CO2H. The relative rates of hydrolysis and hydrazinolysis for different esters are as follows ... 

M CF3SO3H, PhSCH3 or Tl(OCOCF3)3. The 5-adamantyl group is less prone to sulfoxide formation than is the 5-4-methoxybenzyl group. It is also more stable to CF3COOH. 

The 5-(A -methyl-N -phenylcarbamoyl)sulfenyl group (Snm group) produced under these conditions is stable to HF or CF3SO3H. Since there are few acid-stable — SH protective groups, the Snm group should prove to be useful where strong acids are encountered in synthesis. 

The Troc group on tryptophan is stable to CF3COOH, CF3SO3H, and H2 Pd, but can be cleaved with 0.01 M NaOH/MeOH, hydrazine/Me0H/H20, Cd/AcOH/DMF. Cleavage with Zn/AcOH is only partially complete. 

Amino acids were protected by reductive alkylation with salicylaldehyde (NaBH4, KOH, aq. EtOH). The amine is released by treatment with CF3SO3H (TFA, EDT, PhSMe, 2 h, >75% yield). ... 

CF3SO3H Sulfonated and cation exchange Various alcohols and acids 81-94,... 

Sulfonic acid catalysts can also be used to prepare poly(arylene ether sulfone)s, such as (CF3C0)20, polyphosphoric acid (PPA),26 MeS03H-P205 mixture,33 and CF3SO3H.34... 

Mohanty et al. were the first to introduce pendent r-butyl groups in die polymer backbones. The resulting material was quite soluble in aprotic dipolar solvents.83 The PEEK precursors were prepared under a mild reaction condition at 170°C. The polymer precursor can be converted to PEEK in die presence of Lewis acid catalyst A1C13 via a retro Friedel-Crafts alkylation. Approximately 50% of die rerr-butyl substitutes were removed due to die insolubility of the product in die solvent used. Later, Risse et al. showed diat complete cleavage of f< rf-butyl substitutes could be achieved using a strong Lewis acid CF3SO3H as both die catalyst and the reaction medium (Scheme 6.15).84... 

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