Trifluoroacetic propionic anhydride

Rate constants and Arrhenius parameters for the reaction of Et3Si radicals with various carbonyl compounds are available. Some data are collected in Table 5.2 [49]. The ease of addition of EtsSi radicals was found to decrease in the order 1,4-benzoquinone > cyclic diaryl ketones, benzaldehyde, benzil, perfluoro propionic anhydride > benzophenone alkyl aryl ketone, alkyl aldehyde > oxalate > benzoate, trifluoroacetate, anhydride > cyclic dialkyl ketone > acyclic dialkyl ketone > formate > acetate [49,50]. This order of reactivity was rationalized in terms of bond energy differences, stabilization of the radical formed, polar effects, and steric factors. Thus, a phenyl or acyl group adjacent to the carbonyl will stabilize the radical adduct whereas a perfluoroalkyl or acyloxy group next to the carbonyl moiety will enhance the contribution given by the canonical structure with a charge separation to the transition state (Equation 5.24). 

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... 

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 ... 

Like silylation, acetylation is effective as a means to substitute exchangeable hydrogens in alcohols, phenols, and primary and secondary amines. The reagents used for acetylation are acid anhydrides such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride. The reaction temperatures vary between 50 and 150°C and the reaction time from 15 minutes to 2 hours. As for silylation, all traces of water must be avoided. As an example, dopamine acetylation by trifluoroacetic anhydride is presented in Figure 1.5. °... 

The early work was done with acetyl chloride catalyzed with lead acetate [2], propionic and butyric anhydrides in xylene without catalyst [49], and several unsaturated carboxylic acids in the presence of trifluoroacetic anhydride (TFAA) [62,63]. 

The main reasons for derivatization of steroids are to decrease heat sensitivity of steroids to avoid irreversible adsorption of steroids onto the stationary phase to increase volatihty of steroids to increase the separation efficiency to achieve enhanced selectivity of the separations, and to improve the sensitivity of the detectors. Segura et al. described some important general requirements for derivatization reactions, i.e., a single derivative should be formed for each analyte the reaction should be simple and rapid, and they should occur under mild conditions the derivate should be stable, reproducible, and produced with high yield in quantitative analyses, the calibration curve should be linear. The main derivatization method for steroids is silylation, but other derivatization methods using, for example, acetic acid anhydride, trifluoroacetic anhydride (TFA), pentafluoro-propionic acid (PFPA), or heptafluoroabutyric anhydride (HFBA) could also be used. " For anabolic steroids... 

Heating a 3-(2-hydroxyphenyl)propionate ester in diphenyl ether with palladium-charcoal induces a combined cyclization and dehydrogenation [3437], Simultaneous de-O-benzylation and cyclization of a 2-(benzyloxy)acrylic acid by heating with acetyl chloride containing phenyltrimethylammonium iodide gives good yields of a fused pyran-2-one [3836]. In contrast, an o-methoxy-benzylidenemalonic acid (as its potassium salt) cyclizes in the cold when treated with trifluoroacetic acid-trifluoroacetic anhydride [3938]. 

It is interesting that ethane can be converted to propionic acid and its mixed anhydride and trifluoromethyl ethyl ketone under the action of hydrogen peroxide in trifluoroacetic anhydride at 80 °C in the absence of a metal compound [49], The addition of palladium trifluoroacetate resulted in simple oxidation to ethanol and acetaldehyde. 

To evaluate the effects on biological activity of variations in structure of the ester moiety, several semisynthetic esters of maytansinol were prepared. The propionate (230), bromoacetate (231), crotonate (232), and trifluoroacetate (233) esters of maytansinol (229) were made by procedures involving either anhydride-pyridine (230-232) or anhydride-acid (233) treatment. Fig. (58). TTie esters 228, and 230-232 were found to show antileukemic activity comparable to those of the naturally occurring substituted alanyl esters. The trifluoroacetate ester 233 showed no antileukemic activity, possibly because of ready solvolysis in vivo to inactive maytansides. 

For nonpolar and volatile compounds, GC-MS is indeed one of the best online detection techniques, which ideally combines the advantages of the high separation efficiency of capillary GC with high sensitivity and selectivity of the MS detector. GC-NPD and GC-MS techniques have been applied to determine a few HCAs, which require a derivatization step prior to the analysis. A number of derivatizing agents, such as acetic, trifluoroacetic, pentafiuoro-propionic, and heptafiuoro-butyric anhydrides, pentafluoro-benzyl bromide, 3,5-bistrifiuoro-methylbenzyl bromide, and 3,5 bistrifluoro-methylbenzoyl chloride have been tested for the analysis of some HCAs [116],... 

Acetic, propionic, and butyric anhydrides were obtained from Eastman Chemical Company. The purity of each anhydride was greater than 99.9%. Methanesulfonic acid (MSA) and trifluoroacetic anhydride (TFAA) were obtained from Aldrich and were used as received. 

Obtained by acylation of 2-ethyl-l,4-dime-thoxybenzene with propionic acid in the presence of trifluoroacetic anhydride [7605]. 

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