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.     

Double- and triple-consecutive O-insertion into tert-butyl and triarylmethyl structures

[reaction: see text] The concecutive Criegee rearrangement reactions were studied for tert-butyl trifluoroacetate, triarylcarbinols, and benzophenone ketales with trifluoroperacetic acid (TFPAA) in trifluoroacetic acid (TFA). The formation of methyl acetate and methyl trifluoroacetate indicates that the consecutive double-O-insertion process has taken place for tert-butyl trifluoroacetate. The intermediate dimethoxymethylcarbonium ion was detected below 5 degrees C. A consecutive triple-O-insertion process has been observed for triarylmethanols and benzophenone ketals. A new high yield method of corresponding diaryl carbonates synthesis was developed.     

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.     

On the mechanism of the palladium(II)-catalyzed decarboxylative olefination of arene carboxylic acids. Crystallographic characterization of non-phosphine palladium(II) intermediates and observation of their stepwise transformation in Heck-like processes

Mechanistic studies of a palladium-mediated decarboxylative olefination of arene carboxylic acids are presented, providing spectroscopic and, in two instances, crystallographic evidence for intermediates in a proposed stepwise process. Sequentially, the proposed pathway involves carboxyl exchange between palladium(II) bis(trifluoroacetate) and an arene carboxylic acid substrate, rate-determining decarboxylation to form an arylpalladium(II) trifluoroacetate intermediate (containing two trans-disposed S-bound dimethyl sulfoxide ligands in a crystallographically characterized form), then olefin insertion and beta-hydride elimination. Because of the unique mode of generation of the arylpalladium(II) trifluoroacetate intermediate, a species believed to be substantially electron-deficient relative to phosphine-containing arylpalladium(II) complexes previously studied, it has been possible to gain new insights into those steps that are common to the Heck reaction, namely, olefin insertion and beta-hydride elimination. The present results show that there are notable differences in reactivity between arylpalladium(II) intermediates generated by decarboxylative palladation and those produced in conventional Heck reactions. Specifically, we have found that more electron-rich alkenes react preferentially with an arylpalladium(II) trifluoroacetate intermediate formed by decarboxylative palladation, whereas an opposite trend is found in conventional Heck reactions. In addition, we have found that the aralkylpalladium(II) trifluoroacetate intermediates that are formed upon olefin insertion in the present study are stabilized with respect to beta-hydride elimination as compared to the corresponding phosphine-ligated aralkylpalladium(II) complexes. We have also crystallographically characterized an aralkylpalladium(II) trifluoroacetate intermediate derived from arylpalladium(II) insertion into norbornene, and this structure, too, contains an S-bound dimethyl sulfoxide ligand; the ipso-carbon of the transferred aryl group and trifluoroacetate function as the third and fourth ligands in the observed distorted square-planar palladium(II) complex.     

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.     

Synthesis and Properties of Cadmium-containing Quinolinium and Pyrilium Salts

Consecutive treatment of methyl-substituted quinolinium and 2,6-diarylpyrilium perchlorates with sodium ethylate and equimolar amount of anhydrous cadmium(II) trifluoroacetate gives 2- and 4-methylenecadmium-containing salts of the above heterocyclic cations in 80-97% yields. The reactions of the cadmium-containing quinolinium and pyrilium salts with hydrochloric acid, acetic anhydride, mercuric trifluoroacetate, SnCl₂, and nickel(II) trifluoroacetate, resulting in substitution of the CdOCOCF₃ group by hydrogen, Ac, HgOCOCF₃, SnCl, and NiOCOCF₃, respectively, were studied.     

Abraham model correlations for ionic liquid solvents: computational methodology for updating existing ion-specific equation coefficients

The computational methodology for updating existing values of Abraham model ion-specific equation coefficients is illustrated using published experimental solubility and partition coefficient for solutes dissolved in 1-ethyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium trifluoroacetate and 1-hexyl-3-methylimidazolium trifluoroacetate. The updated Abraham model ion-specific equation coefficients that are reported for the trifluoroacetate anion are based on 51 experimental values.     

温和条件下甲烷在熔盐介质中的催化转化

利用硝酸根-硝酸钾(摩尔比0.62:0.38)的熔盐体系作反应介质,以CeO~2,Ce(SO~4)~2,Cu(CF~3CO~2)~2,Co(CF~3CO~2)等为催化剂,在160℃和6.0MPa条件下甲烷被氧化成丙酮和/或三氟醋酸甲酯。甲烷的氯化则可在含氯化铜的氯化铝-氯化钠(摩尔比1:1)的熔盐介质中进行,硫酸银的引入可提高甲烷转化率和一氯甲烷的选择性。     

Reaction of perfluoro carbanions with mercury trifluoroacetate and trifluoromethylmercury trifluoroacetate

Conclusions The reaction of fluoroolefins and alkali metal fluorides with mercury trifluoroacetate and trifluoromethylmercury trifluoroacetate in polar aprotic solvents is a convenient method for the preparation of symmetrical and unsymmetrical bis(perfluoroalkyl)mercury compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1642–1643, July, 1974.     

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.     

Hydration and dielectric properties of aqueous solutions of protonated diallylmethylammonium polymer: transition from monomer to polymer

Abstract

The high-frequency dielectric relaxation of aqueous solutions of protonated diallylammonium polyelectrolyte, namely poly(diallylmethylammonium trifluoroacetate) has been studied at the maximum water dispersion frequencies, 7.5–25?GHz, and temperatures of 288, 298, and 308?K. Dielectric relaxation parameters have been calculated and compared with similar characteristics of aqueous solutions of monomer, diallylmethylammonium trifluoroacetate, and pyrrolidinium trifluoroacetate salt simulated structure of pyrrolidinium polymer link. It has been concluded that although the monomer features hydrophobic hydration, its polymer exhibits hydrophilic hydration properties. This change is related to conformation of hydrophilic-hydrophobic polycations in aqueous solutions and the change in the structure of polymer links.     

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.     

Trifluoroacetate ion-selective electrode

The trifluoroacetate ion-selective electrode was prepared by using the organic solvent solution of trifluoroacetate salt of crystal violet or tris(bathophenanthroline) iron(II) chelate.The response is linear over the activity range 10^?1 to 3 × 10^?5M, with a Nernstian slope 60 mV/activity decade at 29 °C. The interferences of divalent ions, chloride, fluoride and acetate ions are extremely low. Iodide interferes greatly.     

Antarafacial mediation of oxygen delivery by a phenylsulfinyl group in the epoxidation of proximal double bonds: intramolecular trapping of an early Pummerer intermediate with stereoelectronic control

Stereospecific intramolecular antarafacial epoxidation of a double bond via an early Pummerer reaction intermediate has been demonstrated. The intermediate is presumably generated via trifluoroacetylation of a sulfoxide precursor. Ionization of trifluoroacetate would formally generate a dipositive "sulfenium" equivalent. This species attacks an otherwise unactivated, proximal olefinic linkage in an antiperiplanar fashion, with trifluoroacetate serving as the nucleophile. Proposed mechanistic intermediates were characterized structurally (in several cases by crystallographic means) and shown to serve as precursors en route to the final antarafacial epoxides. The sense of the cyclization seems to be driven by principles inherent in Markovnikov's rule.     

Reaction of copper(II) fluoro- and chloroacetates with triphenylphosphine oxide

Triphenylphosphine oxide adducts of copper(II) dichloro-, trichloro- and trifluoroacetate were prepared. Electronic, IR and EPR spectra as well as magnetic data over the temperature range 81–301 K have been mainly used for the determination of the stereochemistry and electronic structure of the adducts. The spectral and magnetic behaviours of the adducts are similar to that of copper(II) acetate hydrate. Some correlations between the magnetic and spectral data as well as the acidity of the respective acids are discussed. Cu(F₃CCOO)₂Ph₃PO, represent the first example of a stable binuclear copper(II) trifluoroacetate adduct.     

Synthesis of 8,9-dioxabicyclo[5.2.1]decane derivatives from cyclooctene

Singlet oxygenation of cyclooctene gives 2-cyclooctenyl hydroperoxide which affords isomeric 2, $\text{cis}$-10-dibromo-8,9-dioxabicyclo[5.2.1]decanes on treatment with mercury(II) trifluoroacetate then bromine, and yields $\text{cis}$-10-bromo-8,9-dioxabicyclo[5.2.1]decane on treatment with bromine then silver trifluoroacetate.     

Anion‐Exchange Properties of Trifluoroacetate and Triflate Salts of N‐Alkylammonium Resorcinarenes

The synthesis of N‐benzyl‐ and N‐cyclohexylammonium resorcinarene trifluoroacetate (TFA) and triflate (OTf) salt receptors was investigated. Solid‐state analysis by single‐crystal X‐ray diffraction revealed that the N‐alkylammonium resorcinarene salts (NARSs) with different upper substituents had different cavity sizes and different affinities for anions. Anion‐exchange experiments by mixing equimolar amounts of N‐benzylammonium resorcinarene trifluoroacetate and N‐cyclohexylammonium resorcinarene triflate, as well as N‐benzylammonium resorcinarene triflate and N‐cyclohexylammonium resorcinarene trifluoroacetate showed that the NARS with flexible benzyl groups preferred the larger OTf anion, whereas the rigid cyclohexyl groups preferred the smaller TFA anions. The anion‐exchange processes were confirmed in the solid state by single‐crystal and powder X‐ray diffraction experiments and in the gas phase by electrospray ionization mass spectrometry.     

离子液体的阴离子三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根的离子对色谱-直接电导检测法分析

建立了同时测定离子液体的阴离子三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根的反相离子对色谱-直接电导检测方法。采用Diamonsil C18分离柱,以离子对试剂-苹果酸-乙腈水溶液为流动相,从流动相组成和色谱柱温度两方面讨论并确定了优化的色谱条件,即以0.15 mmol/L氢氧化四丁铵-0.099 mmol/L苹果酸-20%(v/v)乙腈混合水溶液(pH 6.5)为流动相,柱温25 ℃。在此条件下,三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子均达到基线分离,且不受其他常见阴离子氟离子、氯离子、溴离子、硝酸根、硫酸根的干扰。三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子的检出限(信噪比为3)分别为0.21、0.07、0.36、0.12 mg/L。将方法应用于测定离子液体中三氟乙酸根、硫氰酸根、四氟硼酸根和三氟甲磺酸根离子,加标回收率为95.0%～104.6%。该法简便、快速、灵敏度较高,可满足离子液体样品的检测要求。     

Orientation of nucleophilic substitution in π-cation radicals or π-dications from meso-substituted metalloporphyrins

Treatment of meso-substituted metalloporphyrins [meso -substituent = OCOCF₃, OCOCH₃, OMe, CHO, CN, Cl; metal = Zn(II) or Cd(II)] with thallium(III) trifluoroacetate, followed by an acidic work-up, gives the corresponding β-substituted α-oxophlorins which were either characterised as such or else further derivatised. In all cases the major (or only) disubstitution product has the αβ orientation at the meso positions, indicating that the existing meso substituent directs the incoming one (trifluoroacetate) into the flanking, rather than opposite, meso position of the intermediate π-cation radical or π-dication. In contradistinction, meso substituted zinc(II) porphyrins which are able to lose protons (e.g. α-oxophlorins or α-aminoporphyrins) react with thallium(III) trifluoroacetate, and after a work-up with HCl the corresponding γ-chloro-α-oxophlorin or γ-chloro-α-aminoporphyrin is obtained.     

Two new betaines from the Australian bryozoan Amathia lamourouxi

A chemical investigation of the eastern Australian endemic bryozoan Amathia lamourouxi led to the isolation of two unique betaine molecules, lamouroic acid trifluoroacetate and lamourimidazolinium trifluoroacetate. The structures of these molecules were determined using (+)-HRESIMS, 2D NMR and ECD analyses. The new compounds were screened for antiplasmodial, cytotoxic and antibacterial activity but were inactive at 40 μM. Lamouroic acid trifluoroacetate is structurally related to the ubiquitous marine compound homarine, that has previously been shown to possess feeding deterrent properties, and this suggests that the new compound may also have an ecological role in the bryozoan.