Trifluoroperacetic acid

The syntheses of perhalogenated dithiethanes and their oxidation products (214-219) have been recently reported247. The method is based on the photochemical dimerization of thiophosgen or its fluoro- and bromo-analogues followed by partial oxidation with trifluoroperacetic acid to the desired sulfoxides (or sulfones)248 as shown in equation 84. 

Substitution of the 4-nitro group in 3,4-dinitrofuroxan 1176 by ammonia occurs readily, even at low temperature. Subsequent treatment of the obtained amine, product 1177, with r-butylamine results in formation of 4-amino-2-(/-butyl)-5-nitro-l,2,3-triazole 1-oxide 1178. However, there must be some additional side products in the reaction mixture, as the isolated yield of compound 1178 is only 17%. Upon treatment with trifluoroperacetic acid, the r-butyl group is removed. The obtained triazole system can exist in two tautomeric forms, 1179 and 1180 however, the 1-oxide form 1179 is strongly favored (Scheme 195) <2003CHE608>. 

Some of the important per acids are perbenzoic acid, m-chloroperbenzoic acid, peracetic acid and the powerful trifluoroperacetic acid. Here we shall deal with only perbenzoic acid. 

Baeyer-Villiger reaction of 57 with H3PO5 gives the phenol 59. However, the peracetic acid or trifluoroperacetic acid gives the carboxylic acid 58 (equation 93). Oxidation of V,V-dimethylaniline in aqueous CH3CN at 30 °C affords the V-oxide in 82% yield . 

The oxidation of 3,4-di-/i m-butylthiophene 1,1-dioxide with peracids (MCPBA or trifluoroperacetic acid) affords the corresponding sultone in only moderate yield <1991JOC4001>, though the sultine intermediate could be isolated and characterized structurally. 

N-Nitrosamines have been oxidized to the corresponding N-ni-tramines. Trifluoroperacetic acid and nitric acid/ammonium persulfate are the reagents of choice for this purpose. 

The oxidation of a fluorinated aromatic azo compound has been carried out with a mixture of 89% hydrogen peroxide and trifluoroacetic anhydride it may be considered a trifluoroperacetic acid oxidation [29],... 

CAUTION Due precautions must be taken when handling 89 % hydrogen peroxide and when carrying out this trifluoroperacetic acid oxidation. 

There have been only a few reports of direct hydroxylation362 by an electrophilic process (see, however, 2-26 and 4-5).363 In general, poor results are obtained, partly because the introduction of an OH group activates the ring to further attack. Quinone formation is common. However, alkyl-substituted benzenes such as mesitylene or durene can be hy-droxylated in good yield with trifluoroperacetic acid and boron trifluoride.364 In the case of mesitylene, the product is not subject to further attack ... 

Azaaromatic systems are usually oxidized to their A-oxides. Peracetic acid is the oxidant most used though for unstable substrates perbenzoic or perphthalic acids are preferable. They permit the use of non-polar solvents and milder conditions. Heterocycles relatively inert to oxidation can be converted to N-oxides by the more active performic or trifluoroperacetic acids. m-Chloroperbenzoic acid (MCPBA) also gives good results, especially when other easily oxidizable groups are present in heterocyclic molecule and therefore the question of selectivity is important. Thus, 2-aminopyridine was successfully converted with MCPBA into 2-aminopyridine A-oxide. 

The oxidation of thiazoles by peroxy acids leads to the corresponding A-oxides. Peracetic, MCPBA, permaleic, and trifluoroperacetic acid have been employed for this reaction. Chemical yields range from 4% to 50%, the more basic thiazoles producing higher yields. Thus, thiazole, 2,4-dimethyl- and 4,5-dimethylthiazoles, and 2-phenylthiazole can be oxidized in moderate to good yields. However, neither 4-chloro-2-phenylthiazole nor 5-chloro-2-phenylthiazole could be oxidized. 3-Oxides were also obtained by oxidation of 1,2,3-thiadiazoles and 5-phenylthiatriazole (121—>122) (75T1783). 

Several peroxy acids are need in the conversion of olefins into epoxides. Their properties and preparations have been described by Swem.1<78>1878 Included among them are performio acid, peracetic arid, parbenzoio acid, monoperphthalic acid, and percamphoric acid, Mere recently trifluoroperacetic acid has attained some promi-nenee.S01>1I4fl-1778 Certain desirable features have been discovered in y-nitroperbenzoic arid as well.1 ... 

Conjugated perfluorocyclohepta-1,3-dicne gives by the same epoxidation a mixture of monoepoxide 14 and diepoxycyclohcptane 15.74 Dichlorinated perfluorocyclohexa-1,3-diene 16 is selectively epoxidized to 17 by trifluoroperacetic acid in 22% yield.107 A bicyclic diene, synthesized from perfluorobenzene and 1,2-dichloroethene, is monoepoxidized to give 18 by the same oxidizing agent in 20% yield.108... 

The transformation of carboxylic acids and their functional derivatives to the corresponding peroxycarboxylic acids or diacyl peroxides are generally known reactions.200-201 Among the hydroperoxy derivatives, trifluoroperacetic acid is a frequently used epoxidizing reagent in organic chemistry and is usually prepared in situ.200-201... 

Perfluoronitrosobenzene can be prepared by the oxidation of perfluoroaniline with performic acid in moderate yield.223,226 The same reagent oxidizes 4-bromotetrafluoroaniline (7, X = Br) to the nitroso compound 8 in 64% yield.227 On the other hand, the oxidation of 7 (X = F) with trifluoroperacetic acid in dichloromethanc leads to perfluoronitrobenzene (9) in high yield.228... 

It is possible to oxidize the amino group of 2,3,4.5-tetrafluoro-6-nitroaniline to give the dinitro compound 2.229 The oxidation is successfully accomplished with peroxydisulfuric acid on a scale of 100 mg. but on a 1-g scale violent gassing occurs and most of the product is lost. However, the oxidation is successfully achieved on a 10-g scale, and with a better yield, using trifluoroperacetic acid.229... 

Sodium ra-chloroperbenzoate, 73 Trifluoroperacetic acid, 258 Triphenylsilane-Di-f-butyl peroxide, 334 Phase-transfer catalysts Adogen 464, 258, 281... 

Epoxidation of allylic alcohols with trifluoroperacetic acid offers significantly higher levels of stereocontrol than perbenzoic acid17 (Table 1). 

Oxaadamantane and its derivatives are molecules of considerable interest to chemists and biologists, but until recently there was no convenient route to such compounds. Such a route has now been discovered, starting from the readily accessible 2-hydroxy-2-methyladamantane 1. Thus, oxidation of 1 by trifluoroperacetic acid in TFA at 20°C for one hour gave a mixture (actual yield not given merely described as "a good yield") of three products oxaadamantane 2 (56%), exo-4-hydroxy-2-oxaadamantane 3 (40%) and the lactone 4 (4%). 

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