Interaction of bis(trimethylsilyl)acetylene complex of titanocene with mercury trifluoroacetate

The reaction of the bis(trimethylsilyl)acetylene complex of titanocene Cp₂Ti(Me₃SiC₂SiMe₃) with mercury trifluoroacetate (NF₃COO)₂Hg at 20 °C in a THF medium affords titanocene bis(trifluoroacetate) Cp₂Ti(OCOCF₃)₂ and metallic mercury. The structure of Cp₂Ti(OCOCF₃)₂ was established by the analytical and spectroscopic methods and X-ray diffraction analysis.     

Electrophilic cyclization of α- and β-geranyl acetates by mercury(II) trifluoroacetate

Electrophilic cyclization of β-geranyl acetate promoted by mercury(II) trifluoroacetate leads to mixtures of α- and γ-5αH-cyclogeranyl acetate derivatives and 6α-hydroxy-5αH-and 6α-hydroxy-5βH-cyclogeranyl acetate derivatives mercurated at the C-3 atom. The ratio of the unsaturated and hydroxymercurated products depends on the reaction conditions. α-Geranyl acetate reacts with mercury(II) trifluoroacetate to give a mixture of 6α-hydroxy-5αH-and 6α-hydroxy-5βH-geranyl acetates, mercurated at C-9, with an equatorial mercurated methylene group at C-4. The mercury-containing groups in mercurated cyclogeranyl derivatives can easily be reduced or replaced by an oxygen-containing functional group; this constitutes a convenient route to polyfunctional cyclogeranyl derivatives that are difficult to obtain. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1320–1324, July, 1997.     

Rearrangement and degradation of cephalosporins and penicillins in the presence of mercury(II) trifluoroacetate

[reaction: see text] Cephalosporins and penicillins rearrange under the influence of mercury(II) trifluoroacetate in methanol to non-beta-lactam products. The mechanisms of the rearrangements are different in the two cases. Whereas the open-chain aminoacrylic acid derivative 4 is produced from cephalosporins, the oxazole 7 and the propionamide 6 derivatives are the products from penicillins.     

Microwave dielectric permittivity and relaxation for aqueous potassium trifluoroacetate solutions

The results of microwave dielectric measurements in aqueous potassium trifluoroacetate solutions at seven frequencies (ranging within 7.5–25 GHz) at 288, 298, and 308 K are presented. Static dielectric constants, dielectric relaxation times and activation parameters are calculated. The H-bond network in potassium trifluoroacetate solutions is shown to experience molecular-kinetic stabilization and an increase in connectivity and structuring, which are similar to those experienced by water in potassium acetate solutions. These changes are associated with the hydrophobic hydration of trifluoroacetate ion, which was first determined by microwave dielectric spectroscopy and arises from the effect of the low-polarity CF₃ group of trifluoroacetate ion.     

Iodine labelled radiopharmaceuticals from arylthallium bis(trifluoroacetate) intermediates

A simple, one-step micro-synthesis of aromatic radioiodides which utilizes the in-situ formation of arylthallium bis (trifluoroacetate) intermediates has been developed. Thallium(III) trifluoroacetate was used in the thallation of aryl compounds to yield the intermediate arylthallium bis (trifluoroacetate). The latter was isolated, purified and used for radioiodination. Alternatively, in-situ radioiodination was accomplished by the addition of radioactive aqueous NaI plus excess non-radioactive iodide to complete the reaction. Yields of up to 81% of radiochemically pure compounds were obtained. Using the modified thallation-radioiodination method, aromatic radiopharmaceuticals can be easily and quickly labelled with¹²³I.     

X-ray photoelectron spectra of Rh(III) trifluoroacetate

A study was made of the x-ray photoelectron spectra of Rh(I) and Rh(III) trifluoroacetate complexes. It was shown by using the Cls bond energies of the carboxylate carbon atom as a basis that bridging and monodentate coordination of the trifluoroacetate group could be distinguished with high resolution.Institute of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1549–1551, July, 1992.     

Reaction between silver trifluoroacetate and quercetin in low-polarity organic media

CF₃COOAg-Qr-P systems, where Qr is quercetin and P is an organic solvent, have been studied by spectroscopic methods. The reaction between silver trifluoroacetate and quercetin has been shown to produce colloid solutions, whose destruction terminates with the precipitation of a silver phase. The kinetic characteristics of the reaction between silver trifluoroacetate and quercetin in ethyl acetate have been determined.     

Oxidative aromatization of olefins with dioxygen catalyzed by palladium trifluoroacetate

Molecular oxygen can replace sacrificial olefins as the hydrogen acceptor in the palladium trifluoroacetate catalyzed dehydrogenation of cyclohexene and related cyclic olefins into aromatics. One of the major drawbacks of the homogeneous system is the tendency of the palladium trifluoroacetate to precipitate as palladium(0) at elevated temperatures. The use of better ligands affords catalysts that can operate at higher temperatures, although they are less reactive than palladium trifluoroacetate.     

Fluorine NMR spectra of poly(vinyl trifluoroacetate)

Samples of poly(vinyl trifluoroacetate) with differing stereosequences have been prepared. The NMR signals at 56.4 Mc./sec. corresponding to the three types of triadstereosequences of the trifluoroacetate groups (isotactic, heterotactic, and syndiotactic) can be resolved. The results for specific polymers are discussed.     

GC–MS analysis of phenolic compounds in fuels after conversion to trifluoroacetate esters

The GC–MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported. The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 °C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric C₀-, C₁- and C₂-alkylphenol esters is readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits. In general, mass spectra of trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification. Example applications in analysis of coal-, shale- and petroleum-derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and thermal stress.     

Quantum-chemical study of the silver trifluoroacetate dimer

The results of quantum-chemical calculations of the formation energy, equilibrium structure, and potential surface sections along the nonrigid degrees of freedom of the silver trifluoroacetate dimer are presented. Calculations were performed by the B3LYP method with the cc-pVTZ correlation-coherent basis for C, O, and F atoms using the basis and relativistic effective core potentials Stuttgart 1997 RSC for Ag atoms, and, for comparison, by the HF method in the 6-31G(d) basis and MP2 method in the 6-311G(df) basis for C, O, and F atoms using the basis and relativistic effective core potentials SBKJC for Ag atoms. The eight-membered ring is a rigid planar fragment with a bond order of 0.2 between the silver nuclei. The nearly free internal rotation of the CF₃ group affects the geometrical parameters of the ring. It was substantiated that in electron diffraction experiments, the difficulties of interpretation could be explained not only by the presence of decomposition products in the sample, but also by possible oligomerization of silver trifluoroacetate.     

Nucleophilic trifluoromethylation of aryl halides with methyl trifluoroacetate

When associated with an alkaline halide, such as cesium fluoride or cesium chloride, and Cu(I) species, methyl trifluoroacetate (MTFA) constitutes a valuable trifluoromethylating agent for substituting aromatic (or heteroaromatic) iodides and bromides. The reaction can be carried out in DMF at 180 °C or, better, in sulfolane which allows he reaction to proceed at a lower temperature (from 140 °C).     

Transposition oxy-cope assistee par le trifluoroacetate mercurique en quantite stoechiometrique et en quantite catalytique

Tertiary 1,5-hexadien-3-ols are transformed at room temperature into δ-ethylenic ketones in 35-90%, yields under two sets of conditions: treatment with one molar equivalent of mercuric trifluoroacetate followed by demercuration of the intermediate α-mercuro ketone with sodium borohydride; and treatment with 0.2 molar equivalent of t of lithium trifluoroacetate or trifluorométhansulfonate. The reactions are highly stereoselective, the E isomer of the ketone forming 80-95% of the product. The highest selectivity was observed under the second conditions.     

Trifluoromethylation of carbonyl compounds with sodium trifluoroacetate

In the presence of copper(I) iodide as catalyst, a variety of carbonyl compounds, such as aldehydes, ketones and acid anhydrous, could be trifluoromethylated with sodium trifluoroacetate to give the corresponding alcohols in moderate to high yields, and a possible mechanism was proposed to explain the roles of catalyst and solvent in the reaction system.     

Efficient synthesis of phosphotyrosine building blocks using imidazolium trifluoroacetate

We have successfully employed imidazolium trifluoroacetate as a replacement for tetrazole for efficient synthesis of phosphotyrosine. This modification is compatible with the protecting groups commonly used in solution phase and Fmoc-solid phase peptide synthesis.     

L-arginine trifluoroacetate salt bridges in its solid state compound: the low-temperature three dimensional structural determination of L-arginine bis(trifluoroacetate) crystal and its vibrational spectral analysis

Structural varieties of L-arginine trifluoroacetate (abbreviated as LATF) and L-arginine bis(trifluoroacetate), LABTF, in the solid state compounds were observed and analyzed by the nuclear magnetic resonance (NMR) spectroscopy. The guanidinium-carboxylate interaction plays an important role involving in the crystal structure construction. Conformational changes of L-Arg(+) and L-Arg(2+) cations result from the intrinsic structural difference by hydrogen bonding and electrostatic interactions. The low-temperature structure of its crystalline salt, L-arginine bis(trifluoroacetate), was determined to describe the hydrogen bonding interactions. In comparison with the crystal structure at room temperature, the low-temperature L-Arg(2+) cations present tiny conformational difference and the rotational disorder of CF(3) group disappears. FT-IR and Raman spectra were investigated and hydrogen bonding interactions were analyzed on the basis of its vibrational spectra. Results indicate that this type interaction is greatly contributive to the structural features and vibrational spectral properties.     

Unexpected reaction of 1,1,1,10,10,10-hexafluorodecane-2,4,7,9-tetrone with methyl trifluoroacetate

Hexane-2,5-dione or 1,1,1,10,10,10-hexafluorodecane-2,4,7,9-tetrone react with methyl trifluoroacetate in the presence of LiH to give, upon treatment with diluted acid, 6-hydroxy-9-oxo-2,4,10-tris(trifluoromethyl)-3,11,12-trioxatetracyclo[5,2,1,0^2,6,0^4,10]dodecane. The structure of this compound was determined by X-ray diffraction study.     

Sodium trifluoroacetate: an efficient precursor for the trifluoromethylation of aldehydes

In a convenient and efficient procedure, the nucleophilic trifluoromethylation of aldehydes with sodium trifluoroacetate was achieved, using copper(I) halides as the catalyst.     

Explanation of the selectivity differences between reversed-phase ion-pair chromatographic systems containing trifluoroacetate or heptafluorobutyrate as pairing ion

The well documented selectivity differences found between reversed-phase ion-pair chromatographic systems containing trifluoroacetate or heptafluorobutyrate as pairing ion were explained after determining sorption isotherms for trifluoroacetate and heptafluorobutyrate on Nucleosil 100-5 C₁₈ from a solution similar to the eluents used for the separation of transmitteramines and peptides. Based on the isotherms and retention data obtained with reversed-phase, ion-exchange and reversed-phase ion-pair chromatographic systems, it is proposed that the selectivity differences between the systems studied are caused by the fact that trifluoroacetate and heptafluorobutyrate are not interchangeable in terms of their surface concentrations at the practical eluent concentrations of the pairing ions concerned.     

Reduction of rhodium(III) trifluoroacetate by norbornadiene

It was shown that the action of heat on rhodium(III) trifluoroacetate with norbornadiene (NBD) leads to its reduction and the formation of red crystals of [Rh(CF₃COO)NBD]₂. The formation of the complex was confirmed by elemental analysis and IR, electronic, and x-ray photoelectron spectra. The reaction shows that Rh-Rh compounds can disproportionate under the influence of NBD with the formation of Rh(I) and Rh(III).Institute of Chemical Physics at Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1438–1440, June, 1992.