Trifluoroacetic anhydride TFAA

When 2-lithio-2-(trimethylsilyl)-l,3-dithiane,9 formed by deprotonation of 9 with an alkyllithium base, is combined with iodide 8, the desired carbon-carbon bond forming reaction takes place smoothly and gives intermediate 7 in 70-80% yield (Scheme 2). Treatment of 7 with lithium diisopropylamide (LDA) results in the formation of a lactam enolate which is subsequently employed in an intermolecular aldol condensation with acetaldehyde (6). The union of intermediates 6 and 7 in this manner provides a 1 1 mixture of diastereomeric trans aldol adducts 16 and 17, epimeric at C-8, in 97 % total yield. Although stereochemical assignments could be made for both aldol isomers, the development of an alternative, more stereoselective route for the synthesis of the desired aldol adduct (16) was pursued. Thus, enolization of /Mactam 7 with LDA, as before, followed by acylation of the lactam enolate carbon atom with A-acetylimidazole, provides intermediate 18 in 82% yield. Alternatively, intermediate 18 could be prepared in 88% yield, through oxidation of the 1 1 mixture of diastereomeric aldol adducts 16 and 17 with trifluoroacetic anhydride (TFAA) in... 

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. 

The synthesis of 4,5-diaryl-6-phenylsulfanyl-2,3-benzo-l,3a,6a-triazapentalenes 239 through Pummerer-type reactions of (benzotriazol-l-yl)allylic sulfoxides 238 with trifluoroacetic anhydride in THF has been reported (Equation 35) <2002EJ0493>. Similarly, unstable solid imines 240 treated without purification with trifluoroacetic anhydride (TFAA) provide 241 (Equation 36) <2003TL7507>. 

In 1983, Groves and Takahashi demonstrated that a nitrido-Mnvporphyrin underwent a nitrogen-transfer reaction via a tV-trifluoroacetylnitrenoid species to give an aziridine, when it was treated with trifluoroacetic anhydride (TFAA) in the presence of olefins (Scheme 31).141... 

The reduction of (2,3)-q - and (2,3)-jS-methylenepenam j6-sulfoxides to the corresponding sulfides using potassium iodide and trifluoroacetic anhydride (TFAA) is found to be much faster than for bicyclic jS-lactam jS-sulfoxides.- In the proposed mechanism, initial attack of the sulfoxide oxygen on TFAA is followed by rate-limiting, nucleophilic displacement of trifluoroacetate by iodide ion nucleophilic attack of iodide on the iodine atom then yields the sulfide and iodine. The rate enhancement is accounted for by the stabilization of the transition state in the rate-limiting step by interaction of the p-like orbital of sulfur and the cyclopropane a orbital. 

The A-nitration of the furazan-based heterocycle (29) has been reported. The corresponding tetranitramine (30) is an unstable substance, but obtained on treating (29) with either trifluoroacetic anhydride (TFAA) in nitric acid or dinitrogen pentoxide in nitric acid. In this case the furazan rings stabilize the 1,4,5,8-tetraazadecalin structure and further reduce the basicity of the amidine amino groups. A number of other furazan and nitrogen-rich nitramines... 

A number of reagents derived from nitrate salts and acid anhydrides have been reported for the V-nitration of amides and related compounds. Crivello first reported the use of metal nitrates in trifluoroacetic anhydride (TFAA) for the nitration of aromatic systems. Chapman... 

Miki and Hachiken reported a total synthesis of murrayaquinone A (107) using 4-benzyl-l-ferf-butyldimethylsiloxy-4fT-furo[3,4-f>]indole (854) as an indolo-2,3-quinodimethane equivalent for the Diels-Alder reaction with methyl acrylate (624). 4-Benzyl-3,4-dihydro-lfT-furo[3,4-f>]indol-l-one (853), the precursor for the 4H-furo[3,4-f>]indole (854), was prepared in five steps and 30% overall yield starting from dimethyl indole-2,3-dicarboxylate (851). Alkaline hydrolysis of 851 followed by N-benzylation of the dicarboxylic acid with benzyl bromide and sodium hydride in DMF, and treatment of the corresponding l-benzylindole-2,3-dicarboxylic acid with trifluoroacetic anhydride (TFAA) gave the anhydride 852. Reduction of 852 with sodium borohydride, followed by lactonization of the intermediate 2-hydroxy-methylindole-3-carboxylic acid with l-methyl-2-chloropyridinium iodide, led to the lactone 853. The lactone 853 was transformed to 4-benzyl-l-ferf-butyldimethylsiloxy-4H-furo[3,4- 7]indole 854 by a base-induced silylation. Without isolation, the... 

C-aryl glycals in 75-92% yields. It consisted in the addition of aryllithium reagents to variously protected 2-deoxy-aldono-l,5-lactones, followed by treatment with a mixture of pyridine (Py), 4-(Dimethylamino)pyridine (DMAP), and trifluoroacetic anhydride (TFAA). 

Lastly, a formal synthesis of almotriptan (5) has been published by the Bosch group in Spain using an intramolecular Heck approach (Scheme 23). lodination of aniline 58 with bis(pyridine)iodonium(I) tetrafluoroborate followed by reaction with trifluoroacetic anhydride (TFAA) gave the o-iodotrifluoroacetanilide 66. Alkylation of 66 with methyl 4-bromocrotonate afforded 67, which underwent palladium catalyzed... 

Since the distillate contains 1-3% of the starting acids, P20,j is added to prevent the reaction of TFA and TFAT, which gives trifluoroacetic anhydride (TFAA) and TfOH. 

The activation of DMSO by electrophilic reagents such as oxallyl chloride or trifluoroacetic anhydride (TFAA) (among many others) produces an oxidant capable of oxidizing primary alcohols to aldehydes in high yields. This oxidation is called the Swern oxidation and yields the aldehyde (oxidized product) by reductive elimination of dimethylsulfide (reduced product) and proceeds under mild, slightly basic conditions. It is a second widely used and effective oxidative method for the production of aldehydes from primary alcohols. 

Figure 8. Reaction of oxydemeton methyl with trifluoroacetic anhydride (TFAA) and the GC characteristics of the two products fcis- and tram-dehydro-oxydemeton methyl) on 3% OV-17 at 190°C (34)...

Derivatization of OH Groups. Samples with OH groups at the surface were exposed to trifluoroacetic anhydride (TFAA) vapour for 10-15 min after evacuation to 103 Pa in order to transform the hydroxyl groups into a fluorinated derivate that can much better detected and quantified ... 

The [l,2,4]triazolo[l,5- ]pyridine system is usually constructed by the closure of the triazole ring either by oxidative formation of the NN bond or by condensation of the N-aminopyridine derivatives . Various compounds 78 were obtained by the oxidation of the amidine 77 with Mn02 (Scheme 47) <2003IJB2901, 2005ARK(xiii)21>. A dehydrative cyclization by treatment of formamidoximes 79 with trifluoroacetic anhydride (TFAA) has been used in the synthesis of 80 (Scheme 48), which are key building blocks in the preparation of DPP (IV) inhibitors <2005EJ03761, 2006JME3614>. 

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