Trifluoroacetic anhydride, use

A polar stationary phases such as ODS and TMS and polar such as CN, diol, or NO2 have been successfully applied to the separation of monosaccharides Separation of maltodextrin derivatized with trifluoroacetic anhydride using FID and a CN packed column Capillary supercritical fluid chromatography-MS is well suited to confirm the identity of the TMS derivative of inositol triphosphate Chiral analytes Enantioseparation... 

SAMs of OH-terrninated alkanethiols have been used in many surface modification reactions (Fig. 14). These reacted with OTS to yield a weU-ordered bdayer (322), with octadecyldimethylchlorosilane (323,324), with POCI3 (325—327), with trifluoroacetic anhydride (328), epichlorohydrin (329), with alkyhsothiocyanate (330), with glutaric anhydride (331), and with chlorosulfonic acid (327). 

Bistrifluoroacetamide [407-24-9] M 209.1, m 85 , b 135-136 /744mm, 141 /760mm. Major impurity is trifluoroacetamide. Add trifluoroacetic anhydride, reflux for 2h and fractionate using a Vigreux column at atmospheric pressure. [J Chromatogr 7S 273 1973.]... 

The checkers purchased trifluoroacetic acid from Aldrich Chemical Company, Inc., and distilled it from phosphorous pentoxide. The submitters point out that some trifluoroacetic anhydride, whose effects have not been fully investigated, is obtained under these conditions. The submitters prefer to use trifluoroacetic acid which has been distilled through a glass packed column without the use of a drying agent. 

Carboxylic acids react with trifluoroacetic anhydride to give mixed anhydrides that are especially useful for the acylation of hindered alcohols and phenols ... 

Acylation of various oxygen functions by use of common and commercially available fluonnated carboxylic acid denvatives such as trifluoroacetic anhydride or the corresponding acyl halides have already been discussed sufficiently in the first edition [10] Therefore only exceptional observations will be described in this section In the past 15 years, many denvatizations of various nonfluonnated oxygen compounds by fluoroacylation were made for analytical purposes. Thus Mosher s acid chlorides for example became ready-to-use reagents for the determination of the enantiomeric purity of alcohols and amines by NMR or gas-liquid chromatographic (GLC) techniques [//] (equation 1)... 

A very common oxidizing reagent is peroxytrifluoroacetic acid, which is usually generated in situ from trifluoroacetic acid [29, 30, 31] or trifluoroacetic anhydride [32, 33, 34] and hydrogen peroxide Peroxytrifluoroacetic acid is one of the most efficient epoxidizing reagents [35] It can be used to prepare epoxides... 

Tetrabutylammonium iodide in trifluoroacetic anhydride is an effective reducing reagent [dS] This system can be used for direct reduction of arenesulfonic acids to the corresponding thiols or disulfides m moderate yields under mild conditions (equation 18) Alkanesulfonic acids are reduced by this system to disulfides with 30-57% yields [dfi]... 

Dimethyl sulfoxide reacts with trifluoroacetic anhydride at low tempera ture to give a complex that is an efficient reagent for the oxidation of alcohols to carbonyl compounds [40 41] This reagent can be used to oxidize primary and secondary aliphatic alcohols, cycloalkyl alcohols, and allylic, homoallylic, ben-zylic, acetylenic, and steroidal alcohols (equation 19)... 

In an alternate synthesis of the intermediate ketone, the benzylic halide, 69, is used to alkylate sodium phenoxide. Cyclization of the acid (70) obtained on hydrolysis of the ester by means of trifluoroacetic anhydride again gives 67... 

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. 

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)... 

Using sulfur trioxide a nucleophilic aliphatic carbon and an aromatic nucleus may be connected by a sulfonyl bridge479 (equation 93). Instead of sulfur trioxide, sulfuric acid or chlorosulfonic acid is utilized mostly. The procedures differ mainly by the manner in which the water is eliminated480 e.g., a mixture of sulfuric acid and trifluoroacetic anhydride was used recently481. Similarly to equation 93,3-oxo-2,3-dihydrobenzothiophene 1,1-dioxide is available from acetophenone and chlorosulfonic acid482 (equation 94). 

Using Sodium Iodide with Trifluoroacetic Anhydride or Sulfur Trioxide-Pyridine... 

Using Nitric Acid-Sulfuric Acid-Trifluoroacetic Acid-Trifluoroacetic Anhydride... 

As a general rule, peracetylation is most useful for compounds below Mr 2000, particularly those that have been reduced with sodium borohydride and still contain some salt. The best procedure for peracetylation is based on the method of Bourne and coworkers. Samples are dissolved in 2 1 (v/v) trifluoroacetic anhydride-acetic acid and the solutions kept for 10 min at room temperature. Reagents are removed under a stream of nitrogen, and a solution of the product in chloroform is washed with water to remove salts, and dried the peracetylated sample is dissolved in methanol for the f.a.b. analysis. 

Several alternative procedures have been developed in which other reagents replace carbon monoxide as the migration terminus.11 The most generally applicable of these methods involves the use of cyanide ion and trifluoroacetic anhydride (TFAA). In this reaction the borane initially forms an adduct with cyanide ion. The migration is induced by N-acylation of the cyano group by TFAA. Oxidation and hydrolysis then give a ketone. 

Acetic anhydride and trifluoroacetic anhydride have both been used in conjunction with nitric acid and zeolite (3. This system give excellent para selectivity in many cases.4 The improved selectivity is thought to occur as a result of nitration within the zeolite pores, which may restrict access to the ortho position see, e.g., Entry 7 in Scheme 11.1. 

Entry 5 is an example of nitration in acetic anhydride. An interesting aspect of this reaction is its high selectivity for the ortho position. Entry 6 is an example of the use of trifluoroacetic anhydride. Entry 7 illustrates the use of a zeolite catalyst with improved para selectivity. With mixed sulfuric and nitric acids, this reaction gives a 1.8 1 para ortho ratio. Entry 8 involves nitration using a lanthanide catalyst, whereas Entry 9 illustrates catalysis by Sc(03SCF3)3. Entry 10 shows nitration done directly with N02+BF4, and Entry 11 is also a transfer nitration. Entry 12 is an example of the use of the N02—03 nitration method. 

Scheme 11.4 shows some other representative Friedel-Crafts acylation reactions. Entries 1 and 2 show typical Friedel-Crafts acylation reactions using A1C13. Entries 3 and 4 are similar, but include some functionality in the acylating reagents. Entry 5 involves formation of a mixed trifluoroacetic anhydride, followed by acylation in 85% H3PO4. The reaction was conducted on a kilogram scale and provides a starting material for the synthesis of tamoxifen. Entry 6 illustrates the use of bismuth triflate as... 

Preparatively useful procedures based on acetic anhydride,25 trifluoroacetic anhydride,26 and oxalyl chloride27 have been developed. The last method, known as the Swern oxidation, is currently the most popular. 

In method B, iV-trifluoroacetylimidazole and carboxylic acids are the acylating reagents. This method is also thought to proceed via a carboxylic trifluoroacetic anhydride. This second system is a very convenient reagent for obtaining aromatic ketones because of the use of free carboxylic acids [97]... 

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