Trifluoracetic acid

Spirooxyphosphoranes 166 were obtained by the cyclodehydration of ortho-carboxyarylmethyl phosphine oxides under acidic conditions (Equation 15) to give 166 (X = Y = 0) in which the oxygens occupy the axial positions. Related spirocyclic azoxyphosphoranes 166 (X = NH, NMe) were synthesized from amidoarylmethyl phosphine oxides and trifluoracetic acid <1996PS241>. 

Olivetol 4.74 g (or equimolar amount of analog), 4.03 g (+) cis or trans p-methadien (2,8)-ol-l (the racemic compound can be used but yield will be one-half), 0.8 g p-toluenesulfonic acid in 250 ml benzene reflux two hours (or use 0.004 Moles trifluoracetic acid and reflux five hours). Cool, add ether, wash with NaHC03 and dry, evaporate in vacuum/to get about 9 g of mixture (can chromatograph on 3 50 g silica gel-benzene elutes the THC benzene ether 98 2 elutes an inactive product then benzene ether 1 1 elutes unreacted olivetol evaporate in vacuum to recover olivetol). 

Nakagami and Yokota (1983) impregnated wood with a solution containing methacrylic acid, trifluoracetic acid and sulphuric acid, to form a covalent bond with the cell wall polymers. The methacrylic-reacted wood was then impregnated with styrene, or methylmethacrylate, to form cross-links with the reacted cell wall polymers. Improved dimensional stability was obtained, although degradation of the wood was also observed. 

Solid-phase [2-i-2-i-2] cycloaddihon was also catalyzed by the Ir complex (Scheme 11.6) [14]. Here, the reachon of a resin-bound dipropargylamine and various monoalkynes proceeded under heating by microwave-irradiation, and isoindoline derivatives were obtained in moderate yield after trifluoracetic acid (TFA)-cleavage of the resin-bound intermediates. 

Methylation analysis was run by the method of Hakomori ( ), followed by hydrolysis with trifluoracetic acid, sodium borohydride reduction, and acetylation. 6LC was performed on a Hewlett-Packard 5970, used as an inlet for a mass spectrometer. Molecular weight was determined on a Sephacryl S-500 column (2.6 x 70 cm), using deionized water as solvent, upward flow, 2.75 ml/min, and detection by refractive index monitor. Model R-401 (Waters Associates). 

Alkanes are functionalised by anodic oxidation in acetonitrile, methanol, acetic acid and more acidic solvents such as trifluoracetic acid and fluorosulphuric acid. Reaction requires very positive electrode potentials (see Table 2.1) and platinum has generally been used as anode materials in laboratory scale experiments. On a larger scale carbon is used as anode material. The first stage in these reactions in-... 

Aliphatic ketones are oxidised in both acetonitrile [1,2] and trifluoracetic acid [3] at potentials less positive than required for the analogous hydrocarbons. The oxidation process is irreversible in both solvents and cyclic voltammetry peak potentials are around 2.7 V V5. see. Loss of an electron from the carbonyl oxygen lone pair is considered to be the first stage in the reaction. In acetonitrile, two competing processes then ensue. Short chain, a-branched ketones cleave the carbon-carbonyl bond to give the more stable carbocation, which is then quenched by reaction with... 

The stability of the uracil dimer is the subject of conflicting reports. Ishihara reports33 that it is destroyed by IN NaOH at 100°C, and Wacker states that it is unstable in acid, alkali, or even in boiling water. Setlow et al.46 report that 50% of the uracil dimer is destroyed by formic acid hydrolysis (presumably at 175°C). But Smith32 found it to be stable to boiling water, IN NH4OH, IN HC1, and trifluoracetic acid both at room temperature and at 155°C. 

TBR widely used for all sorts of hydrotreatments in petro and commodity chemicals, it is now adopted in finer chemicals. Intermediates hydrogenation includes quinones, sugars, lactones, functional aromatics, etc... Despite continuous operation, small size TBR can be adapted to batch-wise synthesis by multiple recycling of L product. Example trifluoracetic acid hydrogenation [28]. 

Dissolve 20 g (0.13 mol) of the cyano ester in 100 ml of rectified spirit and add a solution of 19.2g (0.295 mol) of pure potassium cyanide (CAUTION) in 40 ml of water. Allow to stand for 48 hours, then distil off the alcohol on a water bath. Add a large excess of concentrated hydrochloric acid and heat under reflux for 3 hours. (CAUTION hydrogen cyanide evolved.) Dilute with water, saturate the solution with ammonium sulphate and extract with four 75 ml portions of ether. Dry the combined ethereal extracts with anhydrous sodium sulphate, and distil off the ether. Recrystallise the residual acid from excess concentrated hydrochloric acid, and dry in the air. The yield of pure 2,2-dimethylsuccinic acid, m.p. 141-142 °C, is 12 g (63%). The p.m.r. spectrum is recorded in trifluoracetic acid and reveals signals at S 1.48 (s, 6H, Me2) and 2.92 (s, 2H, CH2) the hydroxyl proton is not observed. 

Discussion In principle, acetals are cleaved by acid-catalyzed hydrolysis. In most cases aqueous acetic acid, aqueous trifluoracetic acid, dilute HC1 in THF or DOWEX 50W (H+) resin are used. Thus, treatment of 6 with DOWEX ion exchange resin in methanol rapidly furnishes the corresponding 1,2-diol without any further chromatographic purification steps. Generally, polymer supported reagents benefit from the ease of removal from the reaction mixture just by filtration of the insoluble resin. The resulting diol is acetylated by addition of acetic anhydride and pyridine. Final acetal exchange is achieved by acetic anhydride and catalytic amounts of concentrated sulfuric acid. A mixture (2 1) of anomers is obtained. 

In order to illustrate this problem, it is interesting to analize the unsubstituted polyamides prepared from aliphatic diamines and aromatic diacids or from aliphatic diamines and aliphatic diacids. They are only soluble in solvents such as sulphuric acid, trifluoracetic acid, m-cresol, etc. 

Figure 5.5 Tryptic digest of extracellular superoxide dismutase separated by (a) reversed-phase HPLC, using 0.1% (v/v) trifluoracetic acid in an acetonitrile/water gradient, and (b) CZE, using a 100 mM phosphate buffer, pH 2.5. (Reprinted from Ref. 15 with permission.)...

Trifluoracetic acid-promoted cyclization/dehydration is used to construct a dihydropyran-4-one ring during the total synthesis of (—)-maurenone, establishing the relative stereochemistry of the natural product <2006JOC117>. A double aldol reaction forms two dihydropyran-4-one rings during the total syntheses of (—)- and (+)-membrenone C <20030L1729>. 

Fig. 9.3. Tryptic maps of cyctochrome c by (a) nano-LC (250 bar) and (b) pressurized electrochromatography (12 kV, 250 bar (at the inlet vial)). Column 6 cm (20 cm overall length) x 100 pm I.D. packed with ODS (1.5 pm 100 A) eluent 0.1 % v/v trifluoracetic acid in water (pH 2) containing (A) 0 % and (B) 50 % acetonitrile gradient, 0-100 % B in 10 min. Reproduced from [32], with permission.

The same electron transfer mechanism was proposed by Heiba et a/.242 247 and was supported by the observation by ESR of the radical cations of several arenes when they were treated with Co(III) acetate in trifluoracetic acid.248 Cobalt(III) is a stronger oxidant in trifluoracetic acid than in acetic acid217,249 (see later). In some cases (with electron-rich aromatics), radical cations were observed in acetic acid.242 Further evidence for the radical cation mechanism was obtained in the oxidation of p-methoxybenzyl phenyl sulfide.242 The pro-... 

All the recorded derivatives of these systems have the sulfur atom in the fully oxidized state, the N—S02—N grouping being introduced by the use of sulfamide or a substituted derivative. The 3-unsubstituted 2,2-dioxopyrazolo[3,4-c][l,2,6]triazines (176) and (177 R = H) are formed by heating with sulfamide. With the substituted sulfamides, cyclization of the intermediate is achieved with either alcoholic sodium hydroxide or trifluoracetic acid in moderate yields (Scheme 17) <85S190>. In a similar synthesis (Equation (25)) the tetrahydro-2,2-dioxopyrazolo[4,3-c][l,2,6]thiadiazine (179) is formed from the aminopyrazole (178) <76IJC(B)766>. 

Bellott and Wilson72 studied H-bonded dimers formed by trifluoracetic acid with various other carboxylic adds and amides. 

However, the products may also be trifluoroacetates of the hydroxy compounds. Trifluoroacetates are favored with hydroxy compounds such as nonpolar alcohols, which are better nucleophiles than the more acidic alcohols containing polar groups such as trifluoromethyl, or phenols whose acidity is higher than that of nonpolar alcohols by as much as six or seven orders of magnitude. In addition, formation of trifluoroacetates is enhanced by addition of carbon tetrachloride, trifluoroacetic acid, or both. The presence of trifluoracetic acid may affect the reaction equilibrium between the trifluoroacetate of the hydroxy compound and the carboxylic acid by reacting with the byproduct of the reaction, carboxylic acid, and thus increase the formation of the trifluoroacetate (Guldberg-Waage s law). 

Benzo[h]quinoline. In contrast to the case of acridine, the hydrogenation of benzo /t quinolinc over platinum oxide in trifluoracetic acid afforded a mixture of two octahydro derivatives together with a small amount of the 7,8,9,10-tetrahydro derivative, although the octahydro compound hydrogenated in the benzene rings was the major product (eq. 12.56).37... 

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