Acetic trifluoro

The resolution of methyl ethers of D-glucitol as their acetates, trifluoro-acetates, or trimethylsilyl derivatives was examined. For the last compounds, it was found that 2,6- and 3,6-dimethyl ethers are only partly separated, and that the 2- and 3-monomethyl ethers are not separated at all. This result accords with the observation that trimethylsilyl ethers of alditols are often poorly resolved. 

Cellulose acetate / trifluoro acetate / left -> right trifluoroacetic acid... 

It may be necessary to add a small amount of triefhylamine to the mobile phase if basic analytes need to be separated. Similarly, a trace of acetic, trifluoro-acetic or formic acid can be useful for acidic analytes. However, additives should only be used when necessary (simple eluents are less prone to handling errors). 

TABLE in-32. PHENYLATION OF THIAZOLE AND ALKYL-THIAZOLES IN TRIFLUORO ACETIC ACID SOLUTION WITH BEN20YLPEROXIDE (COM-PEirnON WITH BENZENE) AT 80°C (196). 

The greater positive character hence the increased acidity of the O—H proton of 2 2 2 tnfluoroethanol can be seen m the electrostatic potential maps displayed m Figure 1 8 Structural effects such as this that are transmitted through bonds are called indue tive effects A substituent induces a polarization m the bonds between it and some remote site A similar inductive effect is evident when comparing acetic acid and its trifluoro derivative Trifluoroacetic acid is more than 4 units stronger than acetic acid... 

BBr3, CH2CI2, -10°, 1 h -> 25°, 2 h, 80-100% yield. Benzyl carbamates of larger peptides can be cleaved by boron tribromide in trifluoro-acetic acid, since the peptides are more soluble in acid than in methylene chloride. ... 

Z) -4-CHL0R0-4-HEXENYL TRIFLUOROACETATE [Acetic acid, trifluoro-, (Z)-4-chloro-4-hexenyl ester]... 

When acetic anhydride is used in the CF3CCI3 and zinc reaction with aldehydes, the initial addition product undergoes an elimination reaction to give 2-chloro-l,l,l-trifluoro-2-alkenes exclusively [60, 63] (equation 51)... 

The reaction of hippuric acid with a three-fold excess of trifluoro-acetic anhydride gives a 90% yield of 2-phenyl-4-(2, 2, 2 -trifluoro-l -hydroxyethylidene)-5-oxazolone (2). This compound is also obtained... 

Several alternative routes can be used in order to derivatize the carboxy function (Fig. 7-7). Ketones can be transferred by hydrazines and diols to the corresponding hydrazines or acetals. 2,2,2-Trifluoro-l-phenylethylhydrazine [19] is an example of the first group, while 2,3-butanediol or l,4-dimethoxy-2,3-butanediol can be used to form diastereomeric acetals. 

Figure 3 Reversed-phase chromatography of products after alkaline hydrolysis of /3-poly(L-malate), Discrete polymer products are formed, which differ in length by several units of L-malate. The absorbance at 220-nm wavelength was measured, (a) /3-Poly(L-malate) before hydrolysis, (b) After 10-min incubation in 20 mM NaOH at 37°C. (c) After 15 h in 20 mM NaOH at 37°C. (d) After I h in 500 mM NaOH at 100°C. High pressure chromatography (HPLC) on Waters reversed-phase Ci8- i-Bondapak. The methanol gradient (in water-trifluoro acetic acid, pH 3.0) was programmed as follows 0-40 min 0.3-23%, 40-47 min 23-40%, 47-49 min 40%, 49-54 min 40-0%. (d) Inset size exclusion chromatography after 3-min alkaline hydrolysis at pH 10.2. BioSil SEC 250 column of 300 mm x 7.8 mm size, 0.2 M potassium phosphate buffer pH 7.0.

Amino groups are often protected as their tert-butoxycarbonvl amide, or Boc, derivatives. The Boc protecting group is introduced by reaction of the amino acid with di-fert-butyl dicarbonate in a nucleophilic acyl substitution reaction and is removed by brief treatment with a strong organic acid such as trifluoro-acetic acid, CF3C02H. 

Cholane-24-ol, oxidation with dimethyl sulfoxide, dicyclohexylcarbo-di-imide, and pyridinium trifluoro-acetate, 47, 25... 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

The original procedure for the trifluoroacetylation of amino acids used trifluoroacetic anhydride [Acetic acid, trifluoro-, anhydride].4 This reagent, although inexpensive and readily available, has certain disadvantages it is a highly reactive compound and thus has caused undesired reactions such as the cleavage of amide or peptide bonds,5 unsymmetrical anhydrides are formed between the newly formed A-trifluoroacetylamino acids and the by-product trifluoroacetic acid, and excess trifluoroacetic anhydride has caused racemization of asymmetric centers. 

ACETAMIDE, 2,2,2-TRIFLUORO-A -PHENYL [404-24-0],122 Acetic acid, mercuiy(2+) salt [1600-27-7], 11... 

Acetic acid, methoxy- [625-45-6], 70 Acetic acid, phenoxy- [122-59-8], 68 Acetic acid, trifluoro-, anhydride [407-25-0], 125... 

Abietylamine, dehydro-, A tnfluoro- [Acetamide, 2,2,2-trifluoro-/V-[ [1,2,3,4,4a, 9,10,1 Oa-octahydro-l, 4a-dtmethyl-7-(l-methylethyl)-l -phenanthrenyl ] -methyl]-, [17 (la,4ad,10aa))-, 125 Acetamides, A-arylalkyl-, 7 Acetanilide, 2,2,2-tnfluoro- [Acetamide, 2,2,2-tnfluoroTV-phenyl-], 122 Acetic acid, cyano-, methyl ester, 63 Acetic acid, methoxy-, 70 Acetic acid, phenoxy-, 68 Acetic acid, phenyl- [Benzeneacetic acid],... 

For lab prepns, and occasionally in industrial use, more expensive nitrating agents may be employed, as for example solns of nitric acid in inert organic solvents (chlf, carbon tetrachloride, eth, nitromethane, etc), or a soln of nitric acid in phosphoric or acetic acids or in acetic anhydride, trifluoroacetic anhydride or trifluoro-me thane sulfonic acid (Ref 94)... 

Finally, rates of mercuration have been measured using mercuric trifluoro-acetate in trifluoroacetic acid at 25 °C450. The kinetics were pure second-order, with no reaction of the salt with the solvent and no isomerisation of the reaction products rate coefficients (10 k2) are as follows benzene, 2.85 toluene, 28.2 ethylbenzene, 24.4 i-propylbenzene, 21.1 t-butylbenzene, 17.2 fluorobenzene, 0.818 chlorobenzene, 0.134 bromobenzene, 0.113. The results follow the pattern noted above in that the reaction rates are much higher (e.g. for benzene, 690,000 times faster than for mercuration with mercuric acetate in acetic acid) yet the p factor is larger (-5.7) if the pattern is followed fully, one could expect a larger... 

Acetic acid, nitro-, methyl ester, 55, 77, 78 Acetic acid, trifluoro-, 55 70 Acetonitrile, diphenyl-, 55, 94, 102 Acetonitrile, diphenyl-2-(l-ethoxyethenyl)-[ Acetonitrile, diphenyl-2-(l-ethoxy-vinyl)-, 55, 102... 

Following a similar strategy, trifluoro acetyl ketene diethyl acetal was successively condensed with 2-aminothiophenol in the presence of toluene in a multimode microwave oven (8 min at 980 W) to give the 2-(l,l,l-trifluoro-acetonyl)benzothiazole ring in an excellent yield (93%) [14] (Scheme 13). hi this work, the temperature reached during reaction was not controlled reducing the reproducibility of the process. 

This method has been extended to include imines other than A -thia-zolines, hence enabling the synthesis of multi ring-fused 2-pyridones (28,30, and 33, Scheme 8). Thus, by reacting dihydroisoquinoUnes 27 or /1-carboUnes 29 with acyl Meldrum s acid derivatives 24, a set of new ring-fused heterocycles was prepared in moderate to excellent yields (a and b. Scheme 8). These systems were prepared by using trifluoro acetic acid (TFA) as a proton source instead of solutions saturated with HCl (g). The switch of acid proved to be advantageous since it reduced the formation of by-products and increased the isolated yields. From a practical point of view, TFA is also su-... 

When double bonds are reduced by lithium in ammonia or amines, the mechanism is similar to that of the Birch reduction (15-14). ° The reduction with trifluoro-acetic acid and EtsSiH has an ionic mechanism, with H coming in from the acid and H from the silane. In accord with this mechanism, the reaction can be applied only to those alkenes that when protonated can form a tertiary carbocation or one stabilized in some other way (e.g., by a OR substitution). It has been shown, by the detection of CIDNP, that reduction of a-methylstyrene by hydridopenta-carbonylmanganese(I) HMn(CO)5 involves free-radical addition. ... 

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