Aromatic compounds trifluoromethanesulfonic acid

A number of aromatic compounds, such as benzene, toluene, ethylbenzene, o-xylene, mesitylene, chlorobenzene and napthalene have been reacted with the UHP/triflic acid system. A typical procedure for the hydroxylation of aromatics with urea-hydrogen peroxide/ trifluoromethanesulfonic acid involved slowly adding urea-hydrogen peroxide over a period of 3-5 hours to a solution of large excess of aromatic and trifluoromethanesulfonic acid maintained at -10 °C and then allowed to react for... 

In order to achieve high yields, the reaction usually is conducted by application of high pressure. For laboratory use, the need for high-pressure equipment, together with the toxicity of carbon monoxide, makes that reaction less practicable. The scope of that reaction is limited to benzene, alkyl substituted and certain other electron-rich aromatic compounds. With mono-substituted benzenes, thepara-for-mylated product is formed preferentially. Super-acidic catalysts have been developed, for example generated from trifluoromethanesulfonic acid, hydrogen fluoride and boron trifluoride the application of elevated pressure is then not necessary. 

Diaryl sulfones can be formed by treatment of aromatic compounds with aryl sulfonyl chlorides and a Friedel-Crafts catalyst. This reaction is analogous to Friedel-Crafts acylation with carboxylic acid halides (11-14). In a better procedure, the aromatic compound is treated with an aryl sulfonic acid and P2O5 in polypho-sphoric acid. Still another method uses an arylsulfonic trifluoromethanesulfonic anhydride (ArS020S02CF3) (generated in situ from ArS02Br and CF3S03Ag) without a catalyst. ... 

Attempts of further nitration of dinitro derivative 83 under usual conditions failed. Using 100% nitric acid in fluorosulfonic acid or trifluoromethanesulfonic acid, reagents useful for nitration of deactivated aromatic systems led to the formation of moisture-sensitive nitration products, which undergo further oxidation to give o-quinone-like species 84 and 85. Using the latter conditions, compound 86 can be isolated in 20% yield and converted into the tetraoxo derivative 85 by heating at 220°C (Scheme 4) <1996JOC1898>. 

A new synthetic approach to polycyclic aromatic compounds has been developed based on double Suzuki coupling of polycyclic aromatic hydrocarbon bis(boronic acid) derivatives with o-bromoaryl aldehydes to furnish aryl dialdehydes. These are then converted to larger polycyclic aromatic ring systems by either (a) conversion to diolefins by Wittig reaction followed by photocyclization, or (b) reductive cyclization with trifluoromethanesulfonic acid and 1,3-propanediol (Eq. (12)) [30]. 

Bronsted acids stronger than pure (100%) sulfuric acid Hq = —11.9) are classified as super acids [131, 132]. Thus, perchloric acid (HCIO4), fluorosulfonic acid (F—SO3H), and trifluoromethanesulfonic acid (CF3—SO3H) are considered as super acids. Even exceedingly weak basic solvents e.g. carbonyl compounds aromatic, ole-finic, and saturated hydrocarbons) are protonated by these super acids to give the corresponding carbocations [131]. 

Izumi, J. and Mukaiyama, T. 1996. The catalytic Friedel-Crafts acylation reaction of aromatic compounds with carboxylic anhydrides using combined catalysts system of titanium(IV) chloride tris(trifluoromethanesulfonate) and trifluoromethanesulfonic acid. Chem. Lett. 739-740. 

The electrophilic substitution is the most characteristic reaction for these classes of compounds. Compound (21) undergoes standard electrophilic aromatic substitution reactions. Thus it forms the 6-bromo compound (58) with A7-bromosuccinimide and 6,7-dibromo compound (72) with the excess of the same reagent. It also forms the 6-nitro compound (67) with copper(II) nitrate trihydrate and 6,7-dinitro compound (68) with excess of nitronium tetrafluoroborate. The bis(trifluoro-acetoxy)thallium derivative (73) was formed from trithiadiazepine (21) and thallium(III) trifluoro-acetate in refluxing acetonitrile. Without isolation, (73) was directly converted into the pale yellow 6-iodo compound (74) with aqueous potassium iodide, into the 6-cyano compound (75) with copper(I) cyanide, and into methyl trithiadiazepine-6-carboxylate (76) with carbon monoxide and methanol in the presence of palladium chloride, lithium chloride, and magnesium oxide. Compound (21) is acetylated in the presence of trifluoromethanesulfonic acid (Scheme 7) <85CC396,87JCS(P1)217, 91JCS(P1)2945>. 

High-molecular-weight poly(ketone)s and poly(ketone sulfone)s can be prepared by reacting dicarboxylic acids with aromatic compounds in the presence of trifluoromethanesulfonic acid and phosphorus pentoxide for water binding. 

BuUen, J. V. Ridd, J. H. The rearrangement of aromatic nitro compounds. Part 2 the rearrangement of substituted nitrophenols in trifluoromethanesulfonic acid. J. Chem. Soc., Perkin Trans. 2 1990, 1675-1679. 

Friedel-Crafts Reactions. Aluminum trifluoromethanesulfonate has been used for the Friedel-Crafts alkylation reaction of toluene with isopropyl and tert-butyl chlorides (eq 1), and for the acylation of benzene and toluene with acetyl and benzoyl chlorides in low to moderate yields. Intramolecular Friedel-Crafts acylation of an aromatic compound with Meldrum s acid has also been reported using catalytic amounts of Al(OTf)3. Acylation of 2-methoxynaphthalene with acetic anhydride has been reported using Al(OTf)3 and lithium perchlorate as an additive to afford the corresponding 6-acetylated adduct in 83% yield. Effective acylation of arenes with carboxylic acids has also been disclosed using polystyrene-supported Al(OTf)3. ... 

The combination of a secondary benzyl alcohol with Hf(OTf)4 in nitromethane was a highly effective secondary benzylation system. Secondary benzylation of carbon (aromatic compounds, olefins, an enol acetate), nitrogen (amide derivatives), and oxygen (alcohols) nucleophiles was carried out with a secondary benzyl alcohol and 1 mol % of Hf(OTf)4 in the presence of water. Secondary benzyl alcohols and nucleophiles bearing acid-sensitive functional groups (e.g.,icri-butyldimethylsilyloxy and acetoxy groups and methyl/benzyl esters) could be used for alkylation. Hf(OTf)4 was the most active catalyst for this alkylation, and trifluoromethanesulfonic acid (triflic acid, HOTf) also proved to be a good catalyst. In such cases, the catal)fiic activity of metal triflates and HOTf increased in the order La(OTf)3 [Pg.346]

The rare-earth salts of trifluoromethanesulfonic acid (triflic acid) are popular reagents for lanthanide-mediated organic reactions. Especially scandium(III) triflate, Sc(CF3S03)3, and ytterbium(lll) triflate, Yb(CF3S03)3, are often used as mild Lewis acids for reactions in water (Kobayashi et al., 2002). It is therefore surprising that only very few studies of cerium(IV)-mediated reactions describe the use of cerium(IV) triflate, Ce(CF3 803)4 or Ce(OTf)4, as a reagent. This salt was first reported by Kreh et al. (1987), who prepared a solution of cerium(lV) in aqueous triflic acid by electrochemical oxidation of a cerium(III) triflate solution. They illustrated the use of this reagent for oxidation of alkylaromatic and polycyclic aromatic compounds. Imamoto et al. (1990) prepared cerium(IV) triflate by reaction... 

Takeuchi H, Adachi T, Nishiguchi H, Itou K, Koyama K (1993) Direct aromatic amination by azides reactions of hydrazoic acid and butyl azides with aromatic compounds in the presence of both trifluoromethanesulfonic acid and trifluoroacetic acid. J Chem Soc Perkin Trans 1 867-870... 

N-Tfa- and iV-Fmoc-a-amino ketones have been synthesized56 by reaction of some N -heterocycles or benzene with chiral AM Tfa- and Fmoc-a-aminoacyl)benzotriazoles [e.g. (49)] in the presence of aluminium trichloride. Full preservation of chirality was reported. Aromatic side-chains in some of the (a-amineacyl)benzotriazole compounds gave a competitive intramolecular cyclization, again with retention of chirality [e.g. (49) to (50)]. A full report57 on the intramolecular acylation of aromatics with Meldrum s acid derivatives catalysed by metal trifluoromethanesulfonates under mild reaction conditions has appeared [e.g. (51) to (52)]. The method tolerates many functional groups and was extended to the synthesis of 1-tetralones, 1-benzosuberones and donepezil (53). 

On the other hand, rare-earth trifluoromethanesulfonates (rare earth triflate, RE(OTf)3) have been found to work efficiently as Lewis acids even in aqueous media or in the presence of amines [4], A catalytic amount of RE(OTf)3 enables several synthetically useful reactions, for example aldol, Michael, allylation, Mannich, Diels-Alder reactions, etc., to proceed. It has also been demonstrated that a small amount of RE(OTf)3 is enough to complete the reactions and that RE(OTf)3 can easily be recovered from the reaction mixture and can be reused. A key to accomplishing the catalytic processes was assumed to be the equilibrium between Lewis acids and Lewis bases, for example water, carbonyl compounds, and amines, etc. A similar equilibrium was expected between Lewis adds and aromatic ketones, and, thus, RE(OTf)3-catalyzed Friedel-Crafts acylation was investigated [5]. 

Germain A, Conuneyras A (1973) Mechanism of the C-acylation of aromatic and ethylenic compounds. XV. Kinetic study of the formation of acetylium ion in acetic anhydride solutions in the presence of trifluoromethanesulfonic and fluorosulfonic acids. Bull Soc Chim (France)... 

Ketalization. Aluminum trifluoromethanesulfonate efficiently catalyzes the formation of acetals from various aromatic and ahphatic aldehydes and ketones in low catalyst loadings (1 mol%) and in short reaction times in neat conditions (eq 2). The title compound appears to be a mild catalyst for this reaction. Acid-sensitive sUyl ether of sahcylaldehyde was stable in these conditions. Notably, the catalyst could be recycled up to four times without loss of activity. An efficient method for thioacetaUzation of carbonyl compounds has also been described. ... 

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