Peroxytrifluoroacetic acid in oxidation

Peroxytrifluoroacetic acid, in oxidation, of hexamethyl benzene, 48, 87 of polyalkylarenes, 48, 89, 90 Peroxyvanadic acid, 45, 27 Phenanthrene, 9-phenyl-, 46, 91... 

Anhydrous peroxytrifluoroacetic acid is not easy to handle, but the procedure has recently been revised.121 Namely, reaction of urea-hydrogen peroxide complex (UHP) with tri-fluoroacetic anhydride in acetonitrile at 0 °C gives solutions of peroxytrifluoroacetic acid, which oxidize aldoximes to nitroalkanes in good yields (Eqs. 2.58 and 2.59). Ketoximes fail to react under these conditions, the parent ketone being recovered. 

Triketone (57), a key intermediate in the synthesis of 4,4,7,7,11,11-hexanitropentacyclo [6.3.0.0 .0 °.0 ]undecane (61) (Zlj-hexanitrotrishomocubane), has been synthesized independently by both Marchand and co-workers, and Fessner and Prinzach. Marchand and co-workers prepared the trioxime (58) from the corresponding triketone (57). Oxidation of (58) with peroxytrifluoroacetic acid in acetonitrile provides a direct route to the trinitro derivative (59) in 35 % yield, this yield reflecting an efficiency of 70 % for the oxidation of each oxime group. Subsequent oxidative nitration of (59) with sodium nitrite and potassium ferricyanide in aqueous sodium hydroxide yields the target T>3-hexanitrotrishomocubane (61). 

Trifluoroacetic acid (CF3CO3H) sits between peroxyacetic acid and peroxydisulfuric acid in oxidizing potential. Anhydrous solutions of peroxytrifluoroacetic acid in methylene chloride can be prepared by the addition of 90 %+ hydrogen peroxide to a solution of trifluoroacetic anhydride in methylene chloride containing a trace of sulfuric acid. Solutions of peroxytrifluoroacetic acid prepared from less concentrated hydrogen peroxide solution or trifluoroacetic acid are less reactive to arylamines. 

Peroxytrifluoroacetic acid in the presence of sulfuric acid can be employed for the selective one-step oxidation of the saturated side chain of cholestenone [55] (equation 17)... 

Epoxidations and Baeyet Villiger oxidations. This peroxy acid resembles peroxytrifluoroacetic acid in activity, but buffers are not necessary. The report includes two successful epoxidations with the new peroxy acid (and also p-nitro-peroxybenzoic acid) for which peroxytrifluoroacetic acid was of no value. 

Nitroso compounds are formed selectively via the oxidation of a primary aromatic amine with Caro s acid [7722-86-3] (H2SO ) or Oxone (Du Pont trademark) monopersulfate compound (2KHSO KHSO K SO aniline black [13007-86-8] is obtained if the oxidation is carried out with salts of persulfiiric acid (31). Oxidation of aromatic amines to nitro compounds can be carried out with peroxytrifluoroacetic acid (32). Hydrogen peroxide with acetonitrile converts aniline in a methanol solution to azoxybenzene [495-48-7] (33), perborate in glacial acetic acid yields azobenzene [103-33-3] (34). 

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... 

Mesitylene, condensation with dichloro-methyl methyl ether, 47, 1 oxidation with peroxytrifluoroacetic acid and boron trifluoride, 48, 90 Methallyl chloride in alkylation of 2,4-pentanedione with potassium carbonate, 47, 87... 

Some recent advances have been reported in oxime oxidation, including the in situ generation of peroxytrifluoroacetic acid from the reaction of urea hydrogen peroxide complex with TFAA in acetonitrile at 0 °C This method gives good yields of nitroalkanes from aldoximes but fails with ketoximes. 

Olah and co-workers reported the synthesis of 3,3,7,7-tetranitro-cw-bicyclo[3.3.0]octane (139) from the diketone (137).Inthis synthesis treatment of the dioxime of (137) with abuffered solution of peroxytrifluoroacetic acid gives 3,7-dinitro-cw-bicyclo[3.3.0]octane (138), which on oxidative nitration yields (139) in 76 % yield. 

Some substrates show limited solubility in sulfuric acid solutions and this can affect the rate of oxidation. However, the main factor for slow amine oxidation is due to the high concentration of protonated amine under these highly acidic conditions. Under these conditions only weakly basic amines have a high enough concentration of unprotonated form to permit oxidation to occur. As a result, sulfuric acid solutions of peroxydisulfuric acid are only useful for the oxidation of very weakly basic amines. Peroxydisulfuric acid oxidizes trinitrotoluidines to tetranitrotoluenes (Table4.1, Entry 3) but leaves the more basic dinitrotoluidines unaffected. The opposite is true of peroxyacids like peroxytrifluoroacetic acid and so the reagents are very much complementary. 

Tertiary alkyl primary amines can be oxidized to nitro compounds in excellent yields with KMn04.39S This type of nitro compound is not easily prepared in other ways. All classes of primary amine (including primary, secondary, and tertiary alkyl as well as aryl) are oxidized to nitro compounds in high yields with dimethyldioxirane.399 Other reagents that oxidize various types of primary amines to nitro compounds are dry ozone,4,111 various peracids,401 including peracetic and peroxytrifluoroacetic acids, f-butyl hydroperoxide in the presence of certain molybdenum and vanadium compounds,402 F7-H20-MeCN,41123 and sodium perborate.403... 

Dimethyldioxirane in wet acetone oxidizes isocyanates to nitro compounds (RNCO —> RN02).404 Oximes can be oxidized to nitro compounds with peroxytrifluoroacetic acid, among other ways.398 Primary and secondary alkyl azides have been converted to nitro compounds by treatment with Ph3P followed by ozone.405 Aromatic nitroso compounds are easily oxidized to nitro compounds by many oxidizing agents.4416 OS III, 334 V, 367, 845 VI, 803. 

Similar oxidative rearrangements to produce carbonyl compounds have been carried out with thallium(III) nitrate557 or peroxytrifluoroacetic acid-BF3.558 The Jones reagent (Cr03—H2S04) in the presence of a catalytic amount of Hg(II) is also effective.559 Chromyl chloride oxidation, when combined with reductive workup, is a simple, convenient one-step method to convert 2,2-disubstituted 1-alkenes to aldehydes.560,561... 

---