TFA group

CF3COO-succinimidyl, CH2CI2, 0°, 85% yield.These conditions selectively introduced the TFA group onto a primary amine in the presence of a secondary amine. 

Ammonia treatment removes the TFA group, which then releases the phosphate and pyrrolidine through intramolecular cyclization. The analogous pentyl derivative was also prepared. ... 

The synthesis of A-arylindoles from A,A-diaryl-A -trifluoroacetyl enehydrazines, a process analogous to the Fischer indole synthesis, has been studied in various solvents, including water, and in solvent-free conditions. Solvent polarity, or presence, appears to have had little influence on the reaction course. The A-TFA group has been found to be necessary for efficient reaction, with less electron-withdrawing substituents giving slower reactions, and triflyl diverting the reaction course after the... 

In 2006, Fukuyama and coworkers reported their independent synthesis of yatakemycin (150) [64]. The preparation of the left-hand fragment 165 started with dimethoxybenzene derivative 161. Dibromination of 161 in the presence of FeCls, removal of the TFA group, and oxidation provided a dihydroisoquinoline. Treatment with NsCl to form the hemiaminal, and reductive opening using NaBIl, gave cycUzatiOTi precursor 162. Amination using Cul to give the desired indoline. 

The reagent MBTFA was used first by Donike for introducing the TFA group under mild conditions [124]. 

Another approach to prepare polylysine dendrigrafts was reported by Tsogas et Here, TFA-Lys NCA was oligomerized in aqueous buffer, followed by removal of the TFA groups... 

The selective protection of secondary amines is accomplished by indirect methods after blocking of the primary amines. A typical procedure is shown in Scheme 7. Therein, Tfa (142) partially or fully protects spermine at its primary amines, while the remaining amines can eventually be saturated with Boc-groups (128). After cleavage of the Tfa group with aqueous NaOH, three different Boc-spermines are obtained. By choosing the excesses of ethyltrifluoroacetate the amounts of di- and tri-Boc-spermine can be controlled. Both are helpful synthetic building blocks for solution and solid phase chemistry. 

Scheme 7 Representative synthesis of di- and tri-Boc protected spermine (167b, 168b). The Tfa group (142) is used for temporary blocking the primary amines. Di- and tri-Boc-spermine are obtained in 18% and 43% yield after chromatographic purification by vacuum liquid chromatography. Reagents and conditions a 1.2 eq Tfa-OEt, MeOH, -50 °C b B0C2O, MeOH, 0 °C c NaOHconc/H20 [216].

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