The facile addition of fluorosulfuric acid to an epoxide

Fluorosulfuric acid, a very poor nucleophile, was found to add to several epoxides, yielding 1,3,2-dioxathiolane 2,2-dioxides. These cyclic sulfates could also be obtained by reacting the epoxides with sulfur trioxide. The intermediacy of the fluorosulfate of a 1,2-diol, which readily cyclized in base, has been demonstrated in one case.     

Cleavage of peptides from benzhydrylamine resins using trifluoromethanesulfonic acid

A general method is described for forming peptide amides by cleavage from benzhydrylamine resin using a mixture of trifluoromethanesulfonic acid, thioanisole and trifluoroacetic acid. This procedure gives comparable results to cleavage by liquid hydrogen fluoride.     

The solubility of group I and group II fluorosulfates in fluorosulfuric acid

The solubilities at 25° of some Group I and Group II fluorosulfates in fluorosulfuric acid have been determined. The solubilities (g fluorosulfates/100 g fluorosulfuric acid) are LiSO₃F, 38.78; NaSO₃F, 80.21; KSO₃F, 63.83; RbSo₃F, 89.43; CsSO₃F, 132.4; MgSo₃F, 0.12; CaSO₃F, 16.39; SrSO₃F, 14.52 and BaSO₃F, 4.67.These results can be rationalized on the basis of lattice and solvation energy considerations. These solubility trends are consistent with those of the corresponding fluorides in hydrogen fluorides.     

Reaction of Carbodiimides with trifluoromethanesulfonic acid

Carbodiimides RN=C=NR (R = i-Pr, c-C₆H₁₁, Ph) react with trifluoromethanesulfonic acid with successive formation of O-triflyl isoureas RNHC(OTf)=NR, the isomeric N-triflyl ureas RN(Tf)C(O)NHR, and symmetrically substituted ureas RNHC(O)NHR. Carbodiimide Me₃SiN=C=NSiMe₃ in the reaction with TfOH undergoes desilylation to afford ester CF₃SO₂OSiMe₃ and unsubstituted carbodiimide (cyanamide), which gives the products of di- and trimerization and urea.     

The interpretion of electrical conductivity measurements of three monoprotonic acids in fluorosulfuric acid

The three metal fluorosulfates Au(SO₃F)₅ and Ta(SO₃F)₅ are soluble in fluorosulfuric acid and behave as monoprotonic acids, as is evident from electrical conductivity measurements and conductometric titrations against the base KSO₃F. Both the specific conductometric measurements in the concentration range of 0–0.050 mol-kg^–1 and the conductometric titration curves are compared to calculated curves. Best fits are achieved by assuming an average degree of association for the Lewis acids of 5 for the Nb-, 3 for the Ta- and 2 for the Au-fluorosulfato species in HSO₃F. Dissociation constants are calculated for various association models and a general order of acidity of Au(SO₃F)₃>Ta(SO₃F)₅>Nb(SO₃F)₅ is suggested, with association in solution occurring in the reverse order.     

Extraction-photometric determination of trifluoromethanesulfonic acid with Methyl Violet

Optimal conditions were found for the formation of ion associates of trifluoromethanesulfonic acid with Methyl Violet. A procedure was developed for the extraction-photometric determination of trifluoromethanesulfonic acid in the air of the working area and atmospheric air.     

Dimerization of methylstyrenes by acetyl perchlorate and trifluoromethanesulfonic acid

Ring-substituted methylstyrenes (p-, m-, and o-methylstyrenes) in conjunction with acetyl perchlorate (AcClO₄) or trifluoromethanesulfonic acid as catalysts gave their linear unsaturated dimer in high yield in benzene at temperatures from 50 to 70°C. In particular, the yield of o-methylstyrene dimer was as high as 90% in the AcClO₄ catalysis at 50°C. The dimer yield depended on solvent and catalyst. The terminal structures of the dimers and higher oligomers were analyzed by NMR spectroscopy. Oligomers with a cyclic terminal structure increased in the products at higher temperature. The dimer yield was improved by codimerizing p-methylstyrene with less reactive m-methylstyrene or styrene with AcClO₄ catalyst. The dimers obtained partly consisted of linear unsaturated codimers.     

Protonation and alkylation of organophosphorus compounds with trifluoromethanesulfonic acid derivatives

Protonation (alkylation) of triphenylphosphine, triethylphosphite, triphenylphosphine oxide, triethylphosphate, hexamethylphosporamide, and dimethylphosphite with trifluoromethanesulfonic acid, its bisimide, and methyl ester was studied and the corresponding ¹H, ¹³C, ¹⁹F, ³¹P NMR spectra were analyzed.     

Urea and thiourea complexes with trifluoromethanesulfonic acid and its derivatives

Urea and thiourea form complexes with trifluoromethanesulfonic acid, its monohydrate, and lithium salt CF₃SO₃Li. Urea complexes with trifluoromethanesulfonic acid are also formed as a result of hydrolysis in the reaction of N,N′-bis(trimethylsilyl)carbodiimide or cyanamide with trifluoromethanesulfonic acid in water.     

Electrophilic amination of methylbenzenes with sodium azide in trifluoromethanesulfonic acid

Russian Journal of Organic Chemistry -     

Reaction of 5-phenylpenta-2,4-dienoic acid with benzene in trifluoromethanesulfonic acid

The reaction of 5-phenylpenta-2,4-dienoic acid with benzene in CF₃SO₃H, depending on the reaction conditions, gives three products, namely, 5,5-diphenylpent-2-enoic acid and tetralone and indanone derivatives. These carbocyclic compounds are formed through the addition of two benzene molecules to the starting diene acid and subsequent intramolecular acylation.

     

The acidity constants of some pyrimidine bases in various water-organic solvent media

The acid ionization constants of some pyrimidine bases of nucleic acids were determined pH-metrically at 25 degrees C and at the constant ionic strength I = 0.10 mol l(-1) (KNO3) in pure water as well as in aqueous media containing variable mole percentages (5-30%) of organic solvents. The organic solvents used were methanol, ethanol, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetonitrile, acetone and dioxane. The results obtained indicated that the acidity constants are generally decreased as the content of an organic solvent in the medium is increased. It was deduced that the hydrogen bonding interactions and the solvent basicity in addition to the electrostatic effect are the major effects influencing significantly the acid ionization process of pyrimidine bases in the different water-organic solvent media. Some thermodynamic parameters (deltaH, deltaG degrees, deltaS degrees) of the ionization process over the temperature range 5-45 degrees C in pure water were also determined and discussed.     

A new organocatalyst derived from abietic acid and 4-hydroxy-l-proline for direct asymmetric aldol reactions in aqueous media

Enantioselective direct aldol reactions were carried out in aqueous media with a new organocatalyst that was derived from 4-hydroxy-l-proline and abietic acid via a simple and convenient synthetic protocol with a high overall yield (75%). The new organocatalyst was used for aldol reactions between substituted aromatic aldehydes and various ketones in the presence of several acid additives in aqueous media. The corresponding aldol products were obtained in high isolated yields (up to 99%) and with high anti-diastereoselectivities (up to 94%) and enantioselectivities (>99.9%). The catalyst loading can be efficiently reduced to only 1 mol %. The aldol reactions were found to be extremely fast which is very unusual in organocatalyzed reactions in water.     

The preparation of poly(aryl ether ketones) by the use of trifluoromethanesulfonic acid

Two synthetic routes were used for the preparation of aromatic poly(ether ketones): Friedel-Crafts acylation and aromatic nucleophilic substitution. The first route involved the reaction of diphenyl ether and terephthalic acid dichloride in trifluoromethane-sulfonic acid. The addition of trifluoromethanesulfonic anhydride or phosphorus pentoxide resulted in increased molecular weights. The second synthetic route involved the synthesis of an amorphous tert -butyl-substituted poly(ether ketone) prepolymer. Subsequently, the tert -butyl groups were removed by a reversed Friedel-Crafts alkylation reaction yielding the crystalline polymer PEEK. The dealkylation reaction was performed in trifluoromethanesulfonic acid. The addition of a tert -butyl group acceptor resulted in high dealkylation conversions.     

Spirocyclic systems derived from pyroglutamic acid

The synthesis and likely conformational structure of rigid spirocyclic bislactams and lactam-lactones derived from pyroglutamic acid, and their suitability as lead structures for applications in drug development programmes using cheminformatic analysis, has been investgated.