Chemistry trifluoroacetic anhydride

Trifluoroacetic Anhydride, A New Tool in Organic Chemistry, E. J. Bourne, M. Stacey, and J. C. Tatlow, Abstr. 12th Int. Congr. Pure Appl. Chem. (New York), (1951) 430. 

Abstract Synthesis methods of various C- and /V-nitroderivativcs of five-membered azoles - pyrazoles, imidazoles, 1,2,3-triazoles, 1,2,4-triazoles, oxazoles, oxadiazoles, isoxazoles, thiazoles, thiadiazoles, isothiazoles, selenazoles and tetrazoles - are summarized and critically discussed. The special attention focuses on the nitration reaction of azoles with nitric acid or sulfuric-nitric acid mixture, one of the main synthetic routes to nitroazoles. The nitration reactions with such nitrating agents as acetylnitrate, nitric acid/trifluoroacetic anhydride, nitrogen dioxide, nitrogen tetrox-ide, nitronium tetrafluoroborate, V-nitropicolinium tetrafluoroborate are reported. General information on the theory of electrophilic nitration of aromatic compounds is included in the chapter covering synthetic methods. The kinetics and mechanisms of nitration of five-membered azoles are considered. The nitroazole preparation from different cyclic systems or from aminoazoles or based on heterocyclization is the subject of wide speculation. The particular section is devoted to the chemistry of extraordinary class of nitroazoles - polynitroazoles. Vicarious nucleophilic substitution (VNS) reaction in nitroazoles is reviewed in detail. 

Iminium ion cycUzations such as the Pictet-Spengler reaction have been widely used in alkaloid chemistry to create a carbon-carbon bond between the carbon a to the basic nitrogen and an aromatic ring. The requisite iminium ions in these reactions are often readily available via the modified Polonov-ski reaction. Although two steps, IV-oxide formation and reaction with trifluoroacetic anhydride, are involved, this approach is often preferable to the reaction of a tertiary amine with mercury(II) acetate, in which it is necessary to destroy the amine-mercury complex at the end of the reaction. In this way the secoheteroyohimbinoidiV-oxide (34) was cyclized selectively to uammigine (35 equation 12). Using mercuiy(II) acetate a nearly equal mixture of (35) and its C-3 P-H epimer tetrahydroalstonine is obtained. 

Trifluoroacetic anhydride obtained by action of P203 on the acid is widely used in organic chemistry as an acylating agent in presence of acid. 

Mercury(II) trifluoroacetate [13257-51-7] M 426.6, m 171-173°. It is prepared from HgO and trifluoroacetic acid and is recrystallised from trifluoroacetic anhydride/trifluoroacetic acid. It is a useful reagent for mercuration of aromatic compounds [Lau Kochi J Am Chem Soc 108 6720 1986]. Store it in a tightly stoppered bottle away from light, [cf Aylett in Comprehensive Inorganic Chemistry (Bailer et al. eds) Vol 3 pl87 1973, Beilstein 2 IV 458.] It is very TOXIC and hygroscopic. 

Applications of trifluoroacetic anhydride in carbohydrate chemistry, T. G. Bonner, Adv. Carbohydr. Chem., 16 (1961). 

The synthesis of 3-nitro-l-substituted uracil derivatives 30 can readily be performed with trifluoroacetic nitric anhydride, and this procedure is used in nucleoside chemistry to convert the uracil 3-nitrogen to a good leaving group <1995JA3665, 1997JOC1547, 20020L1827>. 

Chemistry for the Automated C-Terminal Sequence Analysis of Proline Containing Polypeptides. Application of the acetic anhydride/TMS-ITC/TFA procedure, used for the synthesis of TH-proline, to the tripeptide, N-acetyl-Ala-Phe-Pro, in our laboratory, found that thiohydantoin proline was formed in low yield (approx. 1-2% of theoretical). Recovery of the peptide products after the reaction revealed that approximately half of the starting peptide was unchanged and the remaining hdf had been decarboxylated at the C-terminus, thereby blocking it to C-terminal sequence analysis. This was most likely caused by the high concentration of trifluoroacetic acid, the excess of acetic anhydride present, and the high temperature (80°C) at which the reaction was performed. 

---