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The oxidation of both N -substituted hydroxylactams and isoindolinones to the corresponding phthalimides using catalytic iron/ tert -butylhydroperoxide (TBHP) reagent systems is detailed. The 2-substituted-3-hydroxyisoindolin-1-one (hydroxylactam) to imide oxidation constitutes a rather straightforward hydroxyl → carbonyl group conversion while the latter process is a methylene → carbonyl transformation. The iron oxidant Fe (TFA) 3 (10 mol%), prepared by the treatment of iron (III) chloride with trifluoroacetic acid, is used in conjunction with TBHP (one equivalent). For the hydroxylactam substrates, the oxidation system was effective in providing the corresponding phthalimides in isolated yields ranging from 41 to 88% within a reaction time of 24 h. For the N-substituted isoindolinone to phthalimide conversions, the imide products were obtained in isolated yields of 53–96% while using the same catalyst/oxidant system. For comparison, oxidations were run with catalytic iron (III) chloride (10 mol%) and TBHP and the yields were comparable to the reactions using the trifluoroacetate-based reagent. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract A straightforward method to synthesize imidazole derivatives from amidines and sulfoxonium ylides catalyzed by acids is reported in this study. Specifically, catalyzed by trifluoroacetic acid in DCE solvents can improve synthesis efficiency under metal-free conditions. A series of imidazole scaffolds were produced in good to excellent yields. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Simultaneously incorporating heteroatoms and nonbenzenoid aromatic hydrocarbons, such as azulene, into polycyclic aromatic hydrocarbons, offers a robust strategy for designing molecules with aesthetic appeal and unique properties. This study presents the successful synthesis and characterization of a series of azulene-based BO-doped heteroaromatics. Investigation into their optical and electrochemical properties, through UV–vis absorption, cyclic voltammetry, and DFT calculations, reveal their sensitivity to fluoride ions, making them promising candidates for chemosensor applications. Notably, unlike the parent azulene, which is sensitive to acid, these new compounds show negligible changes in absorption and NMR spectra when exposed to excess trifluoroacetic acid. This observation suggests that the introduction of BO unit effectively restrains the protonation of azulene moiety. [Display omitted] • The BO-embedded fused heteroaromatics BOAz-1 , BOAz-2 and BOAz-3 were synthesized. • BOAz-1 , BOAz-2 and BOAz-3 display a selective response to fluoride ion. • The corporation of BO can prevent the azulene moieties from protonation. [ABSTRACT FROM AUTHOR]

1,3-Indandione reacts with 8-quinolinecarbaldehyde to give, depending on the conditions, 2,2'-(quinolin-8-ylmethylene)bis(1 H -indene-1,3(2 H)-dione) 3 or 2-(quinolin-8-ylmethylene)-1 H -indene-1,3(2 H)-dione 4. The 2:1 adduct 3 exhibits dynamic behavior distinct from that of the 2-pyridyl analogue. On cooling, the singlets of the central CH and 2-CH protons resolve into a triplet and doublet, respectively. On heating, all aromatic protons of the two indandione moieties in 3 are averaged due to reversible gear-like rotation of the quinoline fragment driven by the keto-enol tautomerization. In strongly basic DMSO, adduct 3 is reversibly fragmented into 1,3-indandione and 1:1 adduct 4 , the first example of 1:1 adduct of indanones with electron-deficient hetaryl aldehydes. Protonation with trifluoroacetic acid at low temperature reveals the presence of several protonated forms differing by the configuration of the central carbon. Theoretical DFT calculations of adduct 3 , its tautomers, rotamers, transition states and protonated forms were performed to support the experimental results. [Display omitted] [ABSTRACT FROM AUTHOR]

An enamide-based 9-fluorenylmethoxycarbonyl (Fmoc) solid-phase peptide synthesis (SPPS) method was recently disclosed for the synthesis of peptide thioesters. In this manuscript, density functional theory (DFT) calculations were performed to provide deeper mechanistic insights into this reaction. The calculation results clarified the detailed mechanisms of the relevant N-to-S acyl transfer and hydrolysis, the overall rate-determining step, the role of trifluoroacetic acid (TFA), as well as the influence of the stereo-configuration of amide bond and C C bond on reaction rate. [ABSTRACT FROM AUTHOR]

Diversely substituted arylsilyl triflates, as aryne precursors for aryne cycloaddition reactions, were accessed from benzodioxasilines. Catalytic reductive C H ortho- silylation of phenols with traceless acetal directing groups was exploited to prepare benzodioxasilines. Sequential addition of MeLi and then trifluoromethanesulfonic anhydride to benzodioxasilines provided arylsilyl triflates in a single pot. Notably, this approach was successfully utilized to prepare sterically hindered 1,2,3-trisubstituted arylsilyl triflates, which ultimately underwent fluoride-mediated aryne cycloaddition. [ABSTRACT FROM AUTHOR]

The protonation behavior of bicyclo[2.2.2]octadiene (BCOD)-fused thiaporphyrin and thiabenzoporphyrin was examined by titration with trifluoroacetic acid. Neutral, monorotonated, and diprotonated species of thiaporphyrins were easily detected by UV–vis spectral measurement. The first ( K 1 ) and second ( K 2 ) equilibrium constants were found to be K 1 = 520 and K 2 ≈ 7.1 for BCOD-fused thiaporphyrin and K 1 = 1.4 × 10 4 and K 2 ≈ 1.4 for thiabenzoporphyrin. The difference between K 1 and K 2 values of thiaporphyrins is larger than that observed for porphyrins (N 4 -porphyrins). The main contributing conjugation pathways for thiaporphyrins in both protonated species were investigated by NICS and AICD quantum calculations using their atomic geometries obtained by X-ray structural analysis. The 18π-conjugation pathways of the neutral, monoprotonated, and diprotonated species thiaporphyrins were found to contain 18, 19, and 20 atoms, respectively. Results of 1 H NMR studies also support the major contributing pathways. [ABSTRACT FROM AUTHOR]

A novel approach to 2,3,4,5-tetrahydro-1 H -1,4-benzodiazepines starting from N -Boc-protected 2-aminobenzyl alcohols and N -nosyl-protected 2-aminoacetaldehyde dimethyl acetal is presented here. After connection of both building blocks under Mitsunobu conditions, a one-pot cyclization is accomplished with triethylsilane and trifluoroacetic acid. This conversion involves Boc deprotection and an intramolecular reductive N-alkylation. A consecutive methylation at N-1 can be accomplished by adding 1,3,5-trioxane to the reaction mixture. The resulting N4-monoprotected 1,4-benzodiazepines are versatile building blocks for the synthesis of variously substituted drug candidates. [ABSTRACT FROM AUTHOR]

Methods for generating tert -alkyl organoboron species are in high demand as they are invaluable intermediates for the synthesis of quaternary carbon centres. Herein we report investigations into generation of tert -alkyl organoboron species using imidoyl chlorides as reagents in the organoboron cyanidation reaction. Although alkenyl side-products predominate in particularly hindered cases, tert -alkyl organoboron species can be successfully generated for less hindered examples. [ABSTRACT FROM AUTHOR]

Trifluoroacetic acid was found to be effective in intramolecular hydroamination of unfunctionalized olefins bearing electron-rich amino groups, and the corresponding N-heterocycles were obtained in good isolated yields. The scope of the substrates was investigated, and a possible reaction mechanism was proposed. Substituents on CC double bonds and amino groups of the substrates showed drastic effects on the course of the reactions. [ABSTRACT FROM AUTHOR]

Abstract: A highly selective and atom efficient ‘trifluoroacetic ester/ketone metathesis’ has been sincerely witnessed. Enolizable alkyl (at least two non-hydrogen atoms) aryl ketones were found to react readily with ethyl trifluoroacetate under the promotion of NaH to afford trifluoroacetic ester/ketone exchange products, trifluoromethyl ketones (TFMKs), and aromatic acid esters, which were quite different from the general Claisen condensation products, 1,3-diketones. The outcome of the reaction between ketone and ethyl trifluoroacetate is strongly related to the structures of substrates, the steric congestion caused by alkyl group is in favor of the C–C bond cleavage. DFT investigation further disclosed that the metathesis reaction was a kinetically favored pathway. Using only a slight excess of cheap trifluoromethylation reagent, simple operation and mild conditions make it a practical method for preparation of TFMKs on large scale, as well as a new choice of converting aryl alkyl ketones to aromatic acid esters. [Copyright &y& Elsevier]

Abstract: A facile synthesis of 3-hydroxy-3-(trifluoromethyl)-1H-pyrrol-2(3H)-ones based on trifluoroacetic acid-catalyzed condensation–cyclization reactions of β-enamino esters and ethyl trifluoropyruvate is described. These reactions afford a series of α-trifluoromethylated γ-lactam compounds in good to excellent yields under mild conditions. A preliminary trial of an asymmetric catalytic version with chiral BINOL-derived phosphoric acid as enantioselective catalyst was conducted and showed promising enantioselectivity of the desired product. [Copyright &y& Elsevier]

Abstract: A practical three-component copper-mediated oxidative trifluoromethylthiolation of aryl boronic acids with cheap and readily available sodium trifluoroacetate and elemental sulfur is reported. A variety of trifluoromethylthio-substituted aromatics are synthesized in moderate yields under mild reaction conditions. [Copyright &y& Elsevier]

Abstract: Eleven C19-diterpenoid alkaloids reported in Shi's paper were isolated or synthesized. Their 13C NMR and DEPT spectra were recorded using (CD3)2CO+TFA as solvents. Comparison of the acquired NMR data with those reported in Shi's paper, in combination with the fact that all alkaloids, expect for 8, 27, and 28, reported in Shi's paper were isolated using TFA as part of solvent system, led to the following revisions of Shi's paper: (1) compounds 1–4, 6, 7a, 9–26 should be their respective trifluoroacetates. Their structures were revised as 1a–4a, 6a, 7a′, 9a–26a; (2) compounds 7, 27a, and 28a are trifluoroacetates of free bases 8, 27, and 28, respectively; compound 7 should be corrected as 7b; (3) ring A of free bases (such as 8, 27, and 28) exists as chair conformation; while ring A of the protonated versions (such as 7, 27a, 28a, 6a, 9a–26a) exists as boat conformation. Consequently, compounds 7 and 8 are apparently not a pair of conformational isomers, instead, they are indeed a free base and its protonated version existing as a trifluoroacetate, respectively; (4) ‘new’ compounds 6, 13, and 15 are the protonated versions 6a, 13a, and 15a, respectively, of the corresponding known alkaloids, aconifine, deoxyaconitine, 14-benzoylaconine. In addition, all 1H (13C) NMR data for the free bases of new compounds 8, 9, 10, 17, and 24 (Tables 3 and 4) were also assigned based on their 2D NMR spectra. [Copyright &y& Elsevier]

Abstract: In this paper we report the synthesis and crystal structures of emissive organic molecule (1a) based on pyrido[3,4-g]isoquinoline framework as well as its isomers 1b and 1c. The emission quantum yields decrease after transformation of pyridine moieties in 1a into the cyclic-amides in 1b and 1c. The fluorescent spectral results reveal that 1a, 1b, and 1c exhibit no AIE behavior. This is tentatively attributed to intramolecular weak C⋯H interactions, which may impede the intramolecular rotations based on the crystal structures of 1a and 1c. Interestingly, 1a, 1b, and 1c are emissive in the solid state, and among them 1a possesses the highest emission quantum yield (0.22). Moreover, the fluorescence of 1a in solution and solid state can be reversibly tuned by reactions with trifluoroacetic acid and triethylamine. Microarea PL studies reveal that microrods of 1a and these after exposure to HCl gas show typical waveguide behavior. [Copyright &y& Elsevier]

Abstract: An efficient TFA-catalyzed cleavage of C–N bonds in alkylation of indoles by tertiary enamides was described. A variety of bisindolylalkane derivatives, especially 3,3-bisindolylpropanoates, were expeditiously synthesized in good yields. [Copyright &y& Elsevier]

Abstract: Dibenzo[b,f][1,5]diazocines, a class of potential building blocks for novel electrochemical actuators, were synthesized via a novel, efficient acid-catalyzed reaction of 2-acylbenzoisocyanate at room temperature. Real-time NMR analysis and the captured intermediate showed the mechanism was an unprecedented cyclization of the isocyanate with the neighboring acyl group, followed by the dimerization. [Copyright &y& Elsevier]

Abstract: A new, very efficient, and selective preparation method of peralkylated pillar[5]arenes is presented. By replacing typical Lewis acids with trifluoroacetic acid (TFA) we were able to eliminate the need of anhydrous conditions without a loss of effectiveness. The method is highly practical: a) it is moisture-insensitive, b) starting from simple and cheap reagents and reactants, and c) allows for chromatography-free isolation of the products. The results indicate that the interactions with solvent molecules can modulate stability of the products and influence the reaction outcome. Dichloromethane (DCM) and dichloroethane (DCE) are complexed within the cyclopentamer cavity with association constants of 120 M−1 and 600 M−1, respectively (CDCl3). The interactions involve a combination of hydrogen–pi and halogen–pi bonds. [Copyright &y& Elsevier]

Abstract: Enantiopure N β-Fmoc-amino alkyl isonitriles and amino acid esters have been employed as building blocks in Ugi four-component reaction (U-4CR) to yield 1,1′-iminodicarboxylated peptidomimetics. By employing trifluoroacetic acid as one of the components, a different outcome has been observed and rationalized. Ugi products are obtained as trifluoroacetamide adducts, which on further reaction under mild acidic conditions lead to the title compounds. The method has also been proven to be useful for the preparation of ethyl, benzyl and tert-butyl esters. [Copyright &y& Elsevier]

Abstract: The use of zinc salts as cocatalysts in aldol condensations catalyzed by single prolinamide (and in the extension by other more complex prolinamides) can prevent the formation of the parasitic intermediate imidazolidinone, with faster and also more stereoselective reactions than those catalyzed by the free amine. This new finding, together with this ion’s already known properties, make zinc salts highly suitable additives for aldol reactions catalyzed for prolinamide derivatives. [Copyright &y& Elsevier]

Abstract: Efficient synthetic approaches to functionalized 5-(3-R-1-adamantyl)uracils and related compounds (R=OH, COOH, NH2, etc.) are described. The selective hydroxylation of the adamantane tertiary C–H bonds in 5-(1-adamantyl)uracils with H2SO4 in trifluoroacetic anhydride is used as the key step. Subsequent electrophilic reactions of 5-(3-hydroxy-1-adamantyl)uracils with N- and C-nucleophiles in CF3COOH, H2SO4 or H2SO4/AcOH media yielded derivatives with amide, amino, aryl, carboxy and thiourea groups in the adamantane core. The preliminary evaluation of the antiviral activity revealed that some of the synthesized species display moderate antiviral activity against HSV-1 (SI∼20) in Vero cells. [Copyright &y& Elsevier]

Abstract: 2-Arylazo-1-vinylpyrroles 1–6 react with CF3CO2H (benzene, reflux, 5h) in a peculiar way: instead of expected electrophilic addition of CF3CO2H to the N-vinyl group, the latter is transferred to the azo group followed by Neavage to afford substituted 2-methylquinolines 10–12 in up to 56% yields. The reaction was shown (1H, 13C, and 15N NMR) to start with the protonation of the azo group with further inter- and intramolecular involving of two protonated N-vinyl groups to finally build up the quinoline cycle over the aryl moiety. [Copyright &y& Elsevier]

Abstract: Synthesis of coumarins from phenols and propiolic acids was examined by using a Pt catalyst such as PtCl2/AgOTf, K2PtCl4/AgOTf, and K2PtCl4/AgOAc. Propiolic acid reacted even with less reactive phenols in trifluoroacetic acid to give coumarins and dihydrocoumarins. In the case of substituted propiolic acids, phenylpropiolic acid and 2-octynoic acid, the reactions proceeded selectively to afford coumarins in good to high yields. [Copyright &y& Elsevier]

Abstract: Diaryliodonium triflates have been directly prepared by reaction of some iodoarenes with aromatic substrates in good yields by using K2S2O8/CF3COOH/CH2Cl2. Treatment of a variety of iodoarenes with iodobenzene under the same conditions resulted in ligand transfer, and (4-iodophenyl)(phenyl)iodonium triflate was obtained. This procedure avoids the use of high temperature and severe reaction conditions. [Copyright &y& Elsevier]

Abstract: A facile procedure for synthesis of dihydrocoumarin derivatives was described. Although the yield of the products in the reaction of phenols with acrylates in trifluoroacetic acid in the presence of Pd(OAc)2 giving coumarins was found to be very low, dihydrocoumarin derivatives were obtained in good to high yields in the absence of Pd(OAc)2 when ethyl cinnamates bearing electron-donating groups were employed in this reaction. [Copyright &y& Elsevier]

Fusion of aromatic subunits onto porphyrin chromophores produces variable results and in some cases only minor bathochromic shifts are observed. In order to extend these observations, a series of oxa-, thia- and selenaporphyrins with fused acenaphthylene or phenanthrene units have been synthesized. Phenanthro[5,6- b ]porphyrins were previously prepared via conventional '2 + 2' MacDonald condensations, but a more versatile '3 + 1' synthesis is now reported. Phenanthrotripyrranes reacted with a pyrrole dialdehyde in the presence of trifluoroacetic acid, followed by an oxidation step, to give phenanthroporphyrins. However, this chemistry initially gave products that were contaminated with isomeric impurities. Fortunately, good yields of isomerically pure phenanthroporphyrins were obtained when the reactions were carried out under relatively concentrated conditions, and a diphenanthroporphyrin was also obtained using this strategy. An alternative '3 + 1' synthesis was performed where a phenanthropyrrole dialdehyde was condensed with a tripyrrane and this also afforded a phenanthroporphyrin in good yields. Furan, thiophene and selenophene dialdehydes similarly reacted with phenanthro- and acenaphthotripyrranes to give a series of heteroporphyrins with fused phenanthrene and acenaphthylene rings. All of these porphyrinoids retained highly diatropic characteristics. As is the case for tetrapyrrolic porphyrins, the presence of a fused acenaphthylene unit leads to highly modified UV–vis spectra with multiple Soret bands and relatively strong Q bands above 650 nm. However, the longest wavelength absorptions for the acenaphthylene series were only red shifted by 12–15 nm compared to the phenanthrene-fused heteroporphyrin series, which is a somewhat reduced effect compared to previously reported phenanthroporphyrins and acenaphthoporphyrins. Nevertheless, the combined effects of core modification and acenaphthylene ring fusion affords potentially valuable strongly red shifted absorption bands between 677 and 684 nm. [Display omitted] [ABSTRACT FROM AUTHOR]

The sialylation using sialyl donor with 2,6-dimethylbenzyl (DMBn) ester at C-1 carboxy group rapidly proceeded with good α-selectivity to yield sialyl- N -acetylgalactosaminylated 9-fluorenylmethoxycarbonyl (Fmoc) serine unit. The unit was used for the solid-phase peptide synthesis (SPPS) of the sialyl glycopeptide. The DMBn group was removed during the final deprotection by the trifluoroacetic acid (TFA) treatment keeping the sialyl bond intact and the desired sialyl glycopeptide was successfully obtained. This protecting group strategy provided easier access to sialyl glycoamino acids for sialyl glycopeptides synthesis. [Display omitted] [ABSTRACT FROM AUTHOR]

Condensation of methyl 2-acylbenzoates with 2-arylethanamines or 2-acylanilines in the presence of trifluoroacetic acid resulted in the formation of isoindolo[1,2- a ]isoquinolines or isoindolo[2,1- a ]quinolines, respectively, in moderate to excellent isolated yields. [Display omitted] [ABSTRACT FROM AUTHOR]

Reported here is a large oligopyrrole macrocycle, a calix[10]phyrin bearing two diformyl substituents. The combination of conjugation provided by two pentapyrrolic subunits and flexibility resulting from the presence of sp 3 hybridized meso bridges allows the system to adopt a double tailed, scorpiand-like structure with two near-symmetric binding pockets. In methanol solution, this macrocycle was found to interact with a number of test acids, including sulfuric acid, trifluoroacetic acid, phosphoric acid, hydrochloric acid, and fluoroboric acid, via a combination of protonation and counter anion binding. Species specific behavior was seen, allowing for the colorimetric-based discrimination between the acids. Efforts to model the underlying binding equilibria led to the conclusion that upon treatment with excess H 2 SO 4 , up to four protons and two counteranions are bound, whereas in the case of HCl the dominant species is a monoanionic complex. The responses of several other acids were rationalized in terms of these limiting scenarios. [Display omitted] [ABSTRACT FROM AUTHOR]

Spiro[indolizidine-1,3′-oxindole] compounds have been synthesized in enantiomerically pure form from l -glutamic acid. The key oxidative ring contraction of chiral indolo[2,3-a]quinolizidinone was achieved by treatment with N -bromosuccinimide in tetrahydrofuran/water in the presence of catalytic trifluoroacetic acid. The stereochemistry of the reaction was controlled by the dibenzylamino group which could be subsequently removed using Cope elimination. Image 1 • Synthesis of spiro[indolizidine-1,3′-oxindole] in enantiomerically pure form from l -glutamic acid. • Enantio- and diastereodivergent synthesis of four diastereomers of spiro[indolizidine-1,3′-oxindole]. • Synthetic spiro[indolizidine-1,3′-oxindole] with functionalities suitable for further manipulations. [ABSTRACT FROM AUTHOR]