Trifluoracetic anhydride

A General Method of Esterification using Trifluoracetic Anhydride, M. Stacey, E. J. Bourne, J. C. Tatlow, and J. M. Tedder, Nature, 164 (1949) 705. 

An effective reagent for the preparation1 of certain pyrophosphates from the hydrogen phosphates is trifluoracetic anhydride.2... 

Cyclisation of 2-mercaptoacetophenone with trifluoracetic anhydride affords 2-trifluoromethylthiochroman-4-one, from which the thione is available. Unlike the corresponding chromones, the S analogues undergo facile 1,2-additions with TV-nucleophiles... 

When carbanions are generated from the products of reaction between az.irines and foimamidine, a similar process also leads to imidazoles in moderate yields. Azirincs are, however, rather too exotic as substrates to make this an appealing synthetic approach [4]. Treatment of perhydro-l,3-thiazine-2-thione wilh trifluoracetic anhydride gives an imidazothiazine [5]. 

Whereas diiminosuccinonitrile is converted by trifluoracetic anhydride into 27/-imidazoles, these sometimes rearrange at fairly low temperatures (<80°C) to l,2-dialkyl-4,5-dicyanoimidazoles [17, 29, 30. ... 

Redox processes involving 178 have also been studied.Anodic oxidation of thianthrene has been eifected in a wide variety of solvents. Use of trifluoracetic acid gives stable solutions of 178 and, if perchloric acid is included, the solid perchlorate salt may be isolated on evaporation of the solvent after electrolysis. Dichloromethane at low temperatures has been used and, at the opposite extreme, fused aluminum chloride-sodium chloride mixtures. " Propylene carbonate permits the ready formation of 178, whereas the inclusion of water in solvent mixtures gives an electrochemical means of sulfoxidizing thianthrene. Reversible oxidation of 178 to thianthrenium dication may be brought about in customary solvents such as nitriles, nitro compounds, and dichloromethane if the solvent is treated with neutral alumina immediately before voltammetry addition of trifluoracetic anhydride to trifluoracetic acid equally ensures a water-free medium. The availability of anhydrous solvent systems which permit the reversible oxidation and reduction of 178 has enabled the determination of the equilibrium constants for the disproportionation of the radical and for its equilibria with other aromatic materials. ... 

The trifluoracetylation is initiated by deprotonation of the primary carbamate nitrogen, which increases its nucleophilicity compared to the secondary one. The lone pair then attacks the trifluoracetic anhydride. 

Trifluoracetic anhydride, 46,446,458 Trifluoroacetoxylation, 282-283 Trifluoromethanesulfonic acid, 532-533 Trifluoromcthanesulfonic anhydride, 533 Trifluoromethanesulfonic-carboxylic anhydrides, 534... 

The presence of the soft selenium atom and the hard oxygen however, make, the reaction of p-hydroxy selenides site selective. These have in fact been transformed selectively to vinylselenides 7) or olefins4-9,11 12), by selective activation of the hydroxy group, inter alia, with thionyl chloride alone or with thionyl, mesyl and phosphoryl chloride, trifluoracetic anhydride, phosphorus triiodide or diphosphorus tetraiodide in the presence of triethyl amine (Schemes 8Ab 8Bb). The formation of olefins from p-hydroxyselenides is regio- and stereoselective and occurs by formal removal of the hydroxyl and selenenyl moiety in an anti fashion. 

Diiminosuccinonitrile reacts with trifluoracetic anhydride to give 2/f-imidazoles <9iCBi5i7>. (b) Formation of the 1,5- and 4,5-bonds (Scheme 153) ... 

The mechanism of selective purine C(2)-nitration has been investigated and it was demonstrated that this reaction occurs in a three-step process. The reaction was developed with N-9-Boc protected 6-chloropurine 74 and a mixture of tetrabutylammonium nitrate and trifluoracetic anhydride. NMR studies at -50 °C demonstrated that it involved formation and... 

The electronic effects of various substituents in the 6-position are pronounced enough to allow selective monoacylation. Thus 1,2,3,4-tetrahydro-6-nitroquinoxaline is exclusively monoacylated with acetic anhydride or trifluoracetic anhydride at the 4-position. The corresponding 1,4-diacylated derivatives are conveniently prepared by nitration of 1,4-diacetyl- and l,4-bistrifluoroacetyl-l,2,3,4-tetrahydro-quinoxaline, respectively." ... 

A(-benzoylamino)-4,5-dihydro-l-methyl-3-methylthio-1 H-[ 1,2,4]triazole-5-thione (91) upon treatment with trifluoracetic anhydride and trifluoromethanesulfonic acid is converted into the [l,2,4]triazolo[3,4-()][l,3,4]thiadiazolium trifluoromethanesulfonate (92) (Equation (21)) <86LA1540>. 

The synthesis of benzazepines by the acid-catalyzed cyclization of 7 (-(2-arylethyl)-7 (-methyl-2-sulfinylacetamides is a convenient alternative to this acid-catalyzed cyclization. Thus treatment of the amide (172) (Equation (17)) with trifluoracetic anhydride affords the benz(. This method has been used in a first synthesis of the benzopyranobenzazepine alkaloid ( +)-clavizepine <94SL49>. 

Compound (48), 6-O-mycoloyl-MDP results from acylation of the primary hydroxyl group with natural mycolic acid isolated from mycobacterial cells. Its synthesis is illustrated in Fig. 6 (34, 66). The key intermediate (a), a partially protected N-acetyl-muramic acid derivative, can be substituted by a tosyl group at C-6, which can be exchanged with the potassium salt of the mycolic acid in the presence of 18-crown-6 following the method of Polonsky etal. (58). This mild acylation procedure avoids the use of the acid chloride or trifluoracetic anhydride method, which cannot be applied in the present instance because of the presence of a P-hydroxyl group in mycolic acid. The penta-... 

Trifluoroacetic anhydride is a most effective catalyst for the direct esterification of carboxylic acids by primary, secondary, and tertiary alcohols. Esterification proceeds under mild conditions via a mixed anhydride but is not successful with carboxylic acids of very low pKa and hydroxy acids when the reagent promotes lactonisation or polymerization [23, 24]. Dibasic acids may be esterified if they do not readily form cyclic anhydrides. Reagents such as trifluoromethane sulphonic anhydride [25], acetyl chloride [26], pyridine/p-toluene-sulphonyl chloride [27], sulphury chloride [28], thionyl chloride [29], and pyridine/phosphorus oxychloride [30] probably act in a similar way to trifluoracetic anhydride as reagents for direct esterification. 

HDPE [114], Derivatization of the treated PE samples by trifluoracetic anhydride (TFAA) shows that only a minor fraction of oxygen containing surface groups are hydroxyl groups. (It is well known that reaction between TFAA and hydroxyl groups introduces three fluorine atoms for each hydroxyl). A larger amount of fluorine was observed on HDPE [114]. 

In addition, trifluoracetic anhydride has been a useful acid catalyst for the esterification of phenols. The use of heavy metal salts as effective esterification catalysts has been widely reported. For example, BuSnOjH and BujSnO are equal or superior to p-MeC6H4S03H as esterification catalysts and do not effect appreciable dehydration of secondary alcohols. It has been reported that catalytic activities generally descend in the order Sn, Co" , Fe" , Al, Bi, Cr, Sn", Cu, Co Pb, Fe+ Zn, Ni, Mn, Cd, Mg, Ba, K, and CIO4, SO4, PhSOj, Cl, Zr, I, NO3. The use of 1 wt% of Fe2(S04)3 is recommended as a noncorrosive catalyst in steel. 

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