Trifluoroacetic acid anhydride

The trifluoromethyl derivative 146 has been obtained as a minor product from the reaction of (l-methyhndol-3-yl)methanol with trifluoroacetic acid anhydride (TFAA), the major product (22% yield) being 6-trifluoromethylindolo[3,2-()]-carbazole [98LTC(B)841]. Several substituted indolo[2,3-()]carbazoles have also been encountered during studies on the reaction of 4,6-dimethoxyindole with... 

The initial 6,ll-dihydrodibenz[b,e]oxepin-ll-one (7.1.9) is synthesized from the ethyl ester of 2-phenoxymethyl benzoic acid (7.1.7), which is easily synthesized by reacting ethyl 2-bromomethylbenzoate with phenol in the presence of a base. The resulting ester (7.1.5) is hydrolyzed into 2-phenoxymethylbenzoic acid (7.1.8), which is cyclized to 6,11-dihydrodibenz[b,e]oxepin-ll-one (7.1.9) by trifluoroacetic acid anhydride. 

A suspension of potassiumperoxodisulfate in a mixture of trifluoroacetic acid and trifluoroacetic acid anhydride at a methane pressure of 20-30 atmospheres methane and 80-100 °C in the presence of catalytic amounts of 18 and 20 leads to the formation of the trifluoroacetic acid methylester. Scheme 23 shows the oxidative character of the reaction which formally can be described as CH4 [CH3]" -1- H -l- 2e". 

For the catalytic functionalization of methane 0.21 mmol of compoimd 18 and 100 equivalents K2S2O8 are suspended in a mixture of 60 mL trifluoroacetic acid and 10 mL trifluoroacetic acid anhydride and are transferred into an autoclave. With an initial methane pressure of 20 atmospheres and a temperature of 80 °C the only product is trifluoroacetic acid methylester (510% yield relative to palladium). 

The gross structural features, presence of a tetramic acid and E-decenoyl side chain, could be inferred from NMR studies. Methanolysis (HCl/MeOH) of 47 and pentane extraction of the quenched reaction mixture gave two compounds that were determined to be the methyl esters of decenoic acid and N-(2-decenoyl)leucine. The nature of the 3-acyl tetramic acid was deduced from the identification of 48 and 49 in the aqueous portion of the methanolysis reaction mixture following treatment with trifluoroacetic acid anhydride. The unusual C-C bond fragmentation under acidic conditions, and the structure of the antibiotic was confirmed by synthesis of racemic 47 [86]. The configuration at the lone chiral centre was established as R by chiral GC. The carbon NMR spectrum of 47 indicated an equilibrium between three tautomers in which the A2-pyrrolin-4-one form is preferred (60%) and the two internal tautomers (50, 51) make equal contributions (20% each). 

There is an interesting difference in properties between fluoro compounds and the corresponding hydrogen compounds that can be explained by the assumption of the formation of C—H---X bonds. For example, trifluoroacetyl chloride, F CC0C1, has a boiling point below 0°C, whereas that of acetyl chloride is 51°C similarly, trifluoroacetic acid anhydride, (FjCCO O, boils at 20°C and acetic acid anhydride at 137°C. 

The selective oxidation of C—H bonds in alkanes under mild conditions continues to attract interest from researchers. A new procedure based upon mild generation of perfluoroalkyl radicals from their corresponding anhydrides with either H2O2, m-CPBA, AIBN, or PbEt4 has been described. Oxidation of ethane under the reported conditions furnishes propionic acid and other fluorinated products.79 While some previously reported methods have involved metal-mediated functionalization of alkanes using trifluoroacetic acid/anhydride as solvent, these latter results indicate that the solvent itself without metal catalysis can react as an oxidant. As a consequence, results of these metal-mediated reactions should be treated with caution. The absolute rate constants for H-abstraction from BU3 SnH by perfluorinated w-alkyl radicals have been measured and the trends were found to be qualitatively similar to that of their addition reactions to alkenes.80 a,a-Difluorinated radicals were found to have enhanced reactivities and this was explained as being due to their pyramidal nature while multifluorinated radicals were more reactive still, owing to their electrophilic nature.80... 

Acylation reagents (e.g., trifluoroacetic acid anhydride) for amines and alcohols... 

Wear nitrile rubber gloves, laboratory coat, goggles, a face shield, and, if necessary, a self-contained breathing apparatus. Cover the spill with a 1 1 1 mixture by weight of soda ash or calcium carbonate, clay cat litter (bentonite), and sand. When the trifluoroacetic acid (anhydride) has been absorbed, scoop the mixture into an appropriately labeled container for recycling or disposal by burning.4-6... 

To a solution of 2.55 g (12.9 mmol) of daunosamine in 64 ml of dry diethylether under an argon atmosphere 5 ml (4.8 eq.) of pyridine was added. The reaction mixture was cooled to -20°C and 3.63 ml of trifluoroacetic acid anhydride was added. After stirring overnight at room temperature, the mixture was filtered and the filtrate was washed with diethylether. The filtrate was subsequently washed with 10% citric acid solution, saturated NaHC03 and brine. The combined extracts were dried over MgS04, filtrated and evaporated in vacuo. The residue was purified by flash column chromatography (5%... 

Jung and Schurig [7] have investigated enantiomeric separations using capillary SFC and an immobilized cyclodextrin stationary phase of film thickness 0.25 /tm. The authors found no loss in selectivity and column performance after several months. Many NSAID enantiomers could be separated, but amine-containing drugs such as ephedrine or synephrine had to be derivatized with trifluoroacetic acid anhydride prior to assay (see Fig. 

Reaction of antimony pentafluoride with trifluoroacetic acid anhydride yields a binu-clear antimony complex323 ... 

The following class of N-oxide compounds is considerably more stable than the above mentioned peroxides. For example, the oxidation of 3,3 -azobis(6-amino-1,2,4,5-tetrazine) in H202/ CH2C12 in the presence of trifluoroacetic acid anhydride yields the corresponding N-oxide (Fig. 1.16). This compound has a desirable high density and only modest impact and friction sensitivity. 

Phosphoric acid ester amides suffer insertion into the N—H bond (770). Dehydration of 42 with trifluoroacetic acid anhydride and triethylamine yields the ketimide 43. Decomposition of 42 at 170°C leads to recovery of the starting material. 

Carbon disulfide has been found to be inert toward attack of HFA even at elevated temperatures (195). Thiocarboxamides react with two molecules of HFA. The intermediates with the likely structure 134 can be dehydrated with phosphorus oxychloride, pyridine (44), or trifluoroacetic acid anhydride (49) to yield A -l,3,5-oxathiazines 135. A retro Diels-Alder reaction takes place with evolution of HFA when 135 is heated to 140°C (44, 45). The heterobutadienes 136 are in equilibrium with the thiazetes 137, which are more stable at ambient temperature (45). 

Trifluoroacetic acid or trifluoroacetic acid anhydride reacts with hydrox-amic acid amides, thiosemicarbazide, and 1,2-diaminopyridine to yield herbicidal active 1,2,4-oxadiazoles [78GEP(0)2801509], fungicidal-active 1,3,4-thiadiazoles (80USP4264616), and 2-trifluoromethyltriazolo[l,5-alpyridines [80JFC(15)179. 2-Trifluoromethyl-L-histidine was obtained from L-histidine on treatment with benzoyl chloride/sodium hydroxide and subsequent ring closure with trifluoroacetic anhydride (78JOC3403) (Scheme 41). 

The specimens were treated according to the method of Nakagami and coworkers [17,18]. Japanese linden Tilia japonica Smik.) was treated with trifluoroacetic acid anhydride and the fatty acids (TFAA method), which included acetic acid, propionic acid, valeric acid, hexanoic acid, decanoic acid, lauric acid, and palmitic acid. Dynamic measurements were made with a torsion pendulum apparatus under a vacuum. An increasing temperature rate was 2°C/min. The amount of introduced side chain per gram of wood is about 4-6 mmol/g [16]. The chemical structure of the treated wood is presented by the formula ... 

Trifluoroacetic acid anhydride (TFAA) reacts with free amino groups to give the corresponding trifluoroaectamides. For example. 4-aminotetrafluoropyridine (1) is transformed in good yield into the trifluoroacylated product... 

Trifluoroacetic acid anhydride reacts exclusively with the amino moiety of the amino alcohol 5, The trifluoroacetyl group has long been known as a valuable protecting group. ... 

Furthermore, trifluoroacetic acid anhydride treatment of allylic, propargylic, homopropargylic, and some benzylic tertiary 2,4-dimethoxybenzyl amines 7 leads to highly selective cleavage of their benzylic C —N bonds. The resultant trilluoroacetamides (e,g 8a) can then be readily converted into the corresponding secondary amines. ... 

In practice, however, esters are used more often than trifluoroacetic acid anhydride for acylating the amino group, because they are easier to handle. A typical example is the trifluoroacetyla-lion of azelidine (9). ... 

Compound Cu(C0)(02CCF3) CF3C02H is obtained by reacting copper(I) oxide with a trifluoroacetic acid- anhydride mixture under an atmosphere of carbon monoxide the acid solvate molecule may be removed by pumping at room temperature and further such treatment then affords Cu(02CCF3) 219). 

Methanesulfenyl trifluoroacetate, formed in situ by treatment of 5-methyl methanethiosulfi-nate with trifluoroacetic acid anhydride at — 20 °C, undergoes stereoselective addition to a variety of alkenes affording the franj-product 1025. 

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