Nitration Trifluoroacetyl nitrate

A very convenient synthetic procedure for nitration involves the mixing of a nitrate salt with trifluoroacetic anhydride. This presumably generates trifluoroacetyl nitrate. 

Nitration of the potassium enolates of cycloalkanones with pentyl nitrate81 or nitration of silyl enol ethers with nitronium tetrafluoroborate82 provides a method for the preparation of cyclic a-nitro ketones. Trifluoroacetyl nitrate generated from trifluoroacetic anhydride and ammonium nitrate is a mild and effective nitrating reagent for enol acetates (Eq. 2.41).83... 

Nitric acid-trifluoroacetic anhydride mixtures are used extensively for nitrolysis and N-nitration reactions (see Chapters 5 and 6). The same is not true for aromatic nitrations. This reagent contains trifluoroacetyl nitrate, which can ionize to nitronium and trifluoroacetate ions in the presence of strong acid. 

This reagent tends to give high ortho para ratios for some nitrations.2 Another convenient procedure involves reaction of the aromatic compound in chloroform or dichloromethane with a nitrate salt and trifluoroacetic anhydride.3 Presumably, trifluoroacetyl nitrate is generated under these conditions. 

The successful nitration of purines by trifluoroacetyl nitrate was originally presumed to proceed through hetero-lytic dissociation of the reagent into nitroso and trifluoroacetyl radicals, followed by radical attack on the purine <1995TL7875>. However, detailed investigation has shown the reaction mechanism to be a combination of electrophilic and radical steps (see Section 10.11.5.2.3). 

Cerium(IV) ammonium nitrate, 67 Trifluoroacetyl nitrate, 324 Nitroaldol reaction (see Aldol-type reactions)... 

Nitration of 1-arylpyrroles with acetyl nitrate and 1-arylpyrroles and l-(2-ethoxycarbonylbenzyl)pyrrole with trifluoroacetyl nitrate gave 2- and 3-nitro products. 

Exposure of l-acetyl-2-azetine 586 to a point light source resulted in a 1 1 mixture of two adducts in 52% yield, and no other adducts were observed (Equation 229). The conformation of these adducts was confirmed by X-ray analysis of their corresponding iV-nitro analogues after treatment of adducts 587 and 588 with trifluoroacetyl nitrate <1998TL5481>. 

Trifluoroacetyl nitrate is more reactive than acetyl nitrate, and it has been successfully used for the nitration of deactivated aromatics such as nitrobenzene and bromobenzene[31] using fuming nitric acid and trifluoroacetic anhydride in equimolar proportion at 45-55°C. The reaction between trifluoroacetic anhydride and nitric acid gives the nitrating agent trifluoroacetyl nitrate according to Scheme 5.3. 

After our success in nitrating moderately active monosubstituted benzenes with acetic anhydride and nitric acid over zeolite p,11 we decided to try the use of trifluoroacetic anhydride and nitric acid over zeolite p for nitration of deactivated substrates. Although trifluoroacetyl nitrate is known to be more active than acetyl nitrate, it has not been widely used in nitration reactions.15 Nitrobenzene has been successfully nitrated using fuming nitric acid and trifluoroacetic anhydride in equimolar proportions at 45-55 °C.16 However, no dinitration of toluene was reported. 

Such carbamates can be further nitrated, e.g., W-pentafluorosulfanyl-3,3,3-trinitropropyl carbamate is nitrated with trifluoroacetyl nitrate [a mixture of (CF3C0)20 + 100% HN03] to produce AT-pentafluorosul-fanyl-./V-nitro-3,3,3-trinitropropyl carbamate in 43% yield 159). 

In this reaction, considerable nitration of the tosyl groups was observed. The bicycle 89 was obtained in better yield (36%) from 88 by reaction with trifluoroacetyl nitrate in DCM <1996JOC8897, 1998LJSP5831099>. Swern oxidation of the dihydroxy diazocine 90a led to the oxygen-bridged hydroxyl diazocine 91 by transannular hemi-ketalization (Scheme 16) <1996JOC8897>. 

Trifluoroacetyl nitrate, CF3COONO2 (1). The reagent is prepared in situ from ammonium nitrate (NH4NO3) and trifluoroacetic anhydride. 

The reactions of acetyl nitrate, trifluoroacetyl nitrate, and nitronium tetrafluoroborate with enol acetates and trimethylsilyl enol ethers are described in Section 7.2.1.11. 

It has been demonstrated that a mixture of ammonium nitrate and trifluoroacetic anhydride is a very effective system for the nitration of enol acetates. It is assumed that trifluoroacetyl nitrate is produced, which is a much more powerful nitrating agent than acetyl nitrate. So, 2-methyl-2-nitrocyclohexanone... 

A procedure for the efficient synthesis of 1-nitro-1,3-dienes in two steps involves the in situ preparation of trifluoroacetyl nitrate from ammonium nitrate and trifluoioacetic anhydride, and addition to 1,3-dienes to give mixtures of adducts. A mixture of the adducts on treatment with base eliminates to afford... 

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