Trifluoroacetate compounds structure

The ketone shown was prepared in a three step sequence from ethyl trifluoroacetate The first step in the sequence involved treating ethyl tnfluoroacetate with ammonia to give a compound A Compound A was in turn converted to the desired ketone by way of a compound B Fill in the missing reagents in the sequence shown and give the structures of compounds A and B... 

The methacrylic backbone structure makes the spherical Toyopearl particles rigid, which in turn allows linear pressure flow curves up to nearly 120 psi (<10 bar), as seen in Fig. 4.45. Toyopearl HW resins are highly resistant to chemical and microbial attack and are stable over a wide pH range (pH 2-12 for operation, and from pH 1 to 13 for routine cleaning and sanitization). Toyopearl HW resins are compatible with solvents such as methanol, ethanol, acetone, isopropanol, -propanol, and chloroform. Toyopearl HW media have been used with harsh denaturants such as guanidine chloride, sodium dodecyl sulfate, and urea with no loss of efficiency or resolution (40). Studies in which Toyopearl HW media were exposed to 50% trifluoroacetic acid at 40°C for 4 weeks revealed no change in the retention of various proteins. Similarly, the repeated exposure of Toyopearl HW-55S to 0.1 N NaOH did not change retention times or efficiencies for marker compounds (41). 

Many carbamates have been used as protective groups. They are arranged in this chapter in order of increasing complexity of structure. The most useful compounds (not necessarily the simplest structures) are /-butyl (BOC), readily cleaved by acidic hydrolysis benzyl (Cbz or Z), cleaved by catalytic hydrogenol-ysis 2,4-dichlorobenzyl, stable to the acid-catalyzed hydrolysis of benzyl and /-butyl carbamates 2-(biphenylyl)isopropyl, cleaved more easily than /-butyl carbamate by dilute acetic acid 9-fluorenylmethyl, cleaved by /3-elimination with base isonicotinyl, cleaved by reduction with zinc in acetic acid 1-adamantyl, readily cleaved by trifluoroacetic acid and allyl, readily cleaved by Pd-catalyzed isomerization. 

The pyrrolonaphthyridines 208 and 209 can be prepared from rearrangement of the pentacycle 207 upon treatment with trifluoroacetic acid (TFA) (Scheme 52). These products are of interest as they have the same structural skeleton as the indole alkaloid (—)-goniomitine, isolated from the root bark of Gonioma Malagasy <1995JOC3282>. Compound 208 has since been used in the synthesis of further derivatives which show cytotoxic activity against leukemia cells <2001BML79>. 

Combs and coworkers have presented a study on the solid-phase synthesis of oxa-zolidinone antimicrobials by microwave-mediated Suzuki coupling [38], A valuable oxazolidinone scaffold was coupled to Bal resin (PS-PEG resin with a 4-formyl-3,5-dimethoxyphenoxy linker) to afford the corresponding resin-bound secondary amine (Scheme 7.18). After subsequent acylation, the resulting intermediate was transformed to the corresponding biaryl compound by microwave-assisted Suzuki coupling. Cleavage with trifluoroacetic acid/dichloromethane yielded the desired target structures. 

The conversion of alcohols directly into the structurally related hydrocarbons by ionic hydrogenation can provide a means of synthesis for compounds that would be extremely difficult or impossible to obtain by other methods. A good example is the synthesis of 2-terr-butyladamantane (12, R = Me). This interesting, highly strained compound may be synthesized in moderate overall yield by a conventional multiple-step route.149 Alternatively, it is obtained in 90% isolated yield upon treatment of a dichloromethane solution of the readily available 2-/c/7-bulyI -2-adamantanoI (11, R = Me)150 and one equivalent of either tri-n-hexylsilane151152 or triethylsilane153 with trifluoroacetic acid at room temperature (Eq. 16). 

Compound 402 has been prepared in the course of a structure-activity study of new antibacterials <1999BML1339>. The key step for its synthesis relies on an intramolecular Sj Ar reaction from 401, to close the six-membered ring. The yield of this reaction is, however, not mentioned. Dimerization of 2-alkenylthiazolines such as 403 in the presence of trifluoroacetic anhydride provides a straightforward access to 404 <2001TL4937> (Scheme 105). 

To probe the effects of HCFC structure on toxicity the metabolism of three penta-haloethanes, HCFC-123, HCFC-124, and HCFC-125 were studied. The three compounds differ one from the other by the number of fluorine atoms present in the /3-carbon (Fig. 4.64). It was found that the enthalpies of activation, AHact, for hydrogen atom abstraction paralleled the rate of trifluoroacetic acid excretion suggesting that the more difficult it was... 

Rate constants and Arrhenius parameters for the reaction of Et3Si radicals with various carbonyl compounds are available. Some data are collected in Table 5.2 [49]. The ease of addition of EtsSi radicals was found to decrease in the order 1,4-benzoquinone > cyclic diaryl ketones, benzaldehyde, benzil, perfluoro propionic anhydride > benzophenone alkyl aryl ketone, alkyl aldehyde > oxalate > benzoate, trifluoroacetate, anhydride > cyclic dialkyl ketone > acyclic dialkyl ketone > formate > acetate [49,50]. This order of reactivity was rationalized in terms of bond energy differences, stabilization of the radical formed, polar effects, and steric factors. Thus, a phenyl or acyl group adjacent to the carbonyl will stabilize the radical adduct whereas a perfluoroalkyl or acyloxy group next to the carbonyl moiety will enhance the contribution given by the canonical structure with a charge separation to the transition state (Equation 5.24). 

In these latter compounds, the hypervalent iodine may be associated with oxyanions such as perchlorate, trifluoroacetate, and triflate, as verified by the crystal structure of the trifluoroacetate derivative (41). It seems likely that the mode of binding of... 

Although it was first prepared by Verma et al. in 1983 starting from Bi(III) trifluoroacetate [58], our group developed another strategy for the preparation of Bi(OTf)3 [32]. The key point of our synthetic strategy is based on the acidic cleavage of the three carbon-bismuth bonds of triphenylbismuth by triflic acid in dichloromethane (Scheme 1). A study of the hydration of Bi(0Tf)3xH20 revealed that this compound can exist as three different hydrates, the nonahydrate, the tetrahydrate, and the dehydrate [35], The structures of the nona- and tetrahydrate forms have been determined by ab-initio calculations [35] and XRD [36]. 

The gross structural features, presence of a tetramic acid and E-decenoyl side chain, could be inferred from NMR studies. Methanolysis (HCl/MeOH) of 47 and pentane extraction of the quenched reaction mixture gave two compounds that were determined to be the methyl esters of decenoic acid and N-(2-decenoyl)leucine. The nature of the 3-acyl tetramic acid was deduced from the identification of 48 and 49 in the aqueous portion of the methanolysis reaction mixture following treatment with trifluoroacetic acid anhydride. The unusual C-C bond fragmentation under acidic conditions, and the structure of the antibiotic was confirmed by synthesis of racemic 47 [86]. The configuration at the lone chiral centre was established as R by chiral GC. The carbon NMR spectrum of 47 indicated an equilibrium between three tautomers in which the A2-pyrrolin-4-one form is preferred (60%) and the two internal tautomers (50, 51) make equal contributions (20% each). 

Compound (159) has an IR band at 1070 cm-1, in neutral solution or the solid state, consistent with the tetrazole structure. In trifluoroacetic acid this band is replaced by a typical azide absorption at 2140 cm-1. Only in this solvent will photolysis give a good yield (91%) of the pyrimidinoindole (160) (72JOC3216). 

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