Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4

• Elena N. Sigida,
• Yuliya P. Fedonenko,
• Alexander S. Shashkov,
• Nikolay P. Arbatsky,
• Evelina L. Zdorovenko,
• Svetlana A. Konnova,
• Vladimir V. Ignatov and
• Yuriy A. Knirel

Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62

• hydrolysis of the lipopolysaccharide isolated by the phenol–water extraction from the halotolerant soil bacteria Azospirillum halopraeferens type strain Au4. The polysaccharide was studied by sugar and methylation analyses, selective cleavages by Smith degradation and solvolysis with trifluoroacetic acid

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

• Julia Wappel,
• Roland C. Fischer,
• Luigi Cavallo,
• Christian Slugovc and
• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 154–165, doi:10.3762/bjoc.12.17

• stirred methanol and dried. Noteworthy, hydrochloric acid is the only acid which activates the preinitiators under investigation. Addition of other acids (or acid liberating reagents) such as acetyl chloride or trifluoroacetic acid, were not able to promote the polymerization. Also the addition of

Diastereoselective Ugi reaction of chiral 1,3-aminoalcohols derived from an organocatalytic Mannich reaction

• Samantha Caputo,
• Andrea Basso,
• Lisa Moni,
• Renata Riva,
• Valeria Rocca and
• Luca Banfi

Beilstein J. Org. Chem. 2016, 12, 139–143, doi:10.3762/bjoc.12.15

• , by additional crystallization, affording these key intermediates in high ee and de (syn relative configuration, see Supporting Information File 1). The tert-butyl urethane was then deblocked with trifluoroacetic acid. Neutralization and extraction afforded crude aminoalcohols 5a–e, that were directly

Copper-catalyzed intermolecular oxyamination of olefins using carboxylic acids and O-benzoylhydroxylamines

• Brett N. Hemric and
• Qiu Wang

Beilstein J. Org. Chem. 2016, 12, 22–28, doi:10.3762/bjoc.12.4

• efficiencies were observed in the reactions with more acidic benzoic acids, indicating a correlation of their reactivity to their acidity which remains to be further clarified [44]. Furthermore, when trifluoroacetic acid was employed as an oxygen source, the free 1,2-amino alcohol 4g was isolated, possibly due

Selectively fluorinated cyclohexane building blocks: Derivatives of carbonylated all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane

• Mohammed Salah Ayoup,
• David B. Cordes,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2015, 11, 2671–2676, doi:10.3762/bjoc.11.287

• trifluoroacetic acid (TFA) or 6 M HCl in dioxane [10] gave the corresponding benzoic acids 11, 12, and 13 as illustrated in Scheme 1. Direct palladium catalysed formylation of aryl iodides 6/7 as a mixture was explored using Pd(PPh3)4, Bu4SnH and CO [11]. This generated benzaldehyde derivatives 14 and 15 in a 1:3

Carbon–carbon bond cleavage for Cu-mediated aromatic trifluoromethylations and pentafluoroethylations

• Tsuyuka Sugiishi,
• Hideki Amii,
• Kohsuke Aikawa and
• Koichi Mikami

Beilstein J. Org. Chem. 2015, 11, 2661–2670, doi:10.3762/bjoc.11.286

• microreactor, a new protocol for scalable aromatic trifluoromethylation was developed. From a mechanistic aspect, Vicic and co-workers explored the direct generation of CF3Cu from CF3CO2Cu. The use of (N-heterocyclic carbene)copper-trifluoroacetates prepared from trifluoroacetic acid (TFA) was investigated in

• , such as perfluoroalkyl acetates, trifluoroacetic acid, chlorodifluoroacetates, trifluoromethyl ketones and hemiaminals of trifluoroacetaldehyde, are attractive perfluoroalkyl anion sources for aromatic perfluoroalkylation reactions. The generation of perfluoroalkylcopper from perfluoroalkyl carboxylic

• determined by 19F NMR analysis using CF3CH2OH as an internal standard. C–H trifluoromethylation of arenes using trifluoroacetic acid. CF3Cu generated from chlorofluoroacetate and CuI. [18F]Trifluoromethyation with difluorocarbenes for PET. aRadiochemical yield determined by HPLC. Trifluoromethylation with

Easy access to heterobimetallic complexes for medical imaging applications via microwave-enhanced cycloaddition

• Nicolas Desbois,
• Sandrine Pacquelet,
• Adrien Dubois,
• Clément Michelin and
• Claude P. Gros

Beilstein J. Org. Chem. 2015, 11, 2202–2208, doi:10.3762/bjoc.11.239

• trifluoroacetic acid, followed by oxidation under the action of DDQ. Cu and Ga complexes were prepared by the strategy outlined in Scheme 2. The insertion of Cu into corrole 1 was easily achieved with Cu(OAc)2·H2O in THF during 15 min. To obtain the gallium corrole 8b, free-base azidocorrole 1 was dissolved in a

• first dissolved in trifluoroacetic acid (TFA) and stirred at room temperature overnight. A brown oil was obtained upon concentration. The residue was then purified by flash chromatography. Chelation of Cu2+ with propargyl NOTA 4 was performed in aqueous solution by Cu(ClO4)2·6H2O. Purification of Cu

Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyl)oxazoles

• Kandasamy Rajaguru,
• Arumugam Mariappan,
• Rajendran Suresh,
• Periasamy Manivannan and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2015, 11, 2021–2028, doi:10.3762/bjoc.11.219

• Abstract The reaction of α-azidochalcones with carboxylic acids has been investigated resulting in the formation of α-amido-1,3-diketones under microwave irradiation via in situ formation of 2H-azirine intermediates. An interesting reaction is described wherein, with trifluoroacetic acid at lower

• two steps following a literature procedure [29]. Results and Discussion The investigation was initiated by treating α-azidochalcone 1a (R1 = 4-Br, R2 = 4-OMe) with trifluoroacetic acid (2a). This acid was allowed to react with the azidochalcone at room temperature for 30 minutes and a low yield of 3a

• -azidochalcone 1a (R1 = 4-Br, R2 = 4-OMe) with trifluoroacetic acid under microwave conditions [33] at 100 °C for 2 minutes to obtain diketone 3a (79%) as a solid without any side products (Scheme 1). The 1H NMR spectrum of 3a exhibits a methine proton doublet at 6.78 ppm. In the 13C NMR spectrum, two carbonyl

Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• , we proceeded to synthesize complex 4b, featuring the 5-bromo-2-picolinate moiety. Using a similar methodology, the desired complex was obtained with 42% yield. The activation of the new picolinic complex 4a was initially evaluated in the presence of trifluoroacetic acid (TFA), a Brønsted acid easy to

Synthesis and evaluation of the biostability and cell compatibility of novel conjugates of nucleobase, peptidic epitope, and saccharide

• Dan Yuan,
• Xuewen Du,
• Junfeng Shi,
• Ning Zhou,
• Abdulgader Ahmed Baoum,
• Khalid Omar Al Footy,
• Khadija Omar Badahdah and
• Bing Xu

Beilstein J. Org. Chem. 2015, 11, 1352–1359, doi:10.3762/bjoc.11.145

• chain from the resin with 95% trifluoroacetic acid (TFA) without N-protecting groups. Later, NAS was obtained by reacting D-glucosamine hydrochloride with the fully protected NA. After cleaving the protecting group on amino acids with 95% TFA, we used reversed-phase high-performance liquid

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• with trifluoroacetic acid (TFA) in the presence of pentamethylbenzene to generate mycocyclosin (135, 74%) (Scheme 19). Wurtz coupling: The Wurtz reaction is one of the oldest methods to form a C–C bond in organic synthesis. Baker and co-workers [138] have reported the synthesis of cyclophanes 137 and

• acetylenedicarboxylate (DMAD) to deliver compounds 332a,b (77%). These DA adducts were irradiated in diethyl ether/dichloromethane (5:1) to offer the corresponding bioxaquadricyclane 333, subsequent thermolysis gave the bioxepine 334 (81%). Finally, aromatization of bioxepine 334 with trifluoroacetic acid (TFA

Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

• Sultan Taskaya,
• Nurettin Menges and
• Metin Balci

Beilstein J. Org. Chem. 2015, 11, 897–905, doi:10.3762/bjoc.11.101

• reaction time, high yield, and easy isolation of the product 7 (entries 1 and 2, Table 1). We next investigated the isomerization of the double bond in 7, which was treated with trifluoroacetic acid (TFA) in chloroform at room temperature to give 3-methyl-1H-pyrrolo[2,1-c][1,4]oxazin-1-one (6) [27]. After

Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

• Mirko Lohse,
• Larissa K. S. von Krbek,
• Sebastian Radunz,
• Suresh Moorthy,
• Christoph A. Schalley and
• Stefan Hecht

Beilstein J. Org. Chem. 2015, 11, 748–762, doi:10.3762/bjoc.11.85

• . After deprotection of the termini of the attached axles with trifluoroacetic acid (TFA), protonation of the free amines with HCl, and anion exchange with sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate (NaBArF), the target compounds A2 and A4 were obtained. The weakly coordinating BArF counter-ion

Multivalent polyglycerol supported imidazolidin-4-one organocatalysts for enantioselective Friedel–Crafts alkylations

• Tommaso Pecchioli,
• Manoj Kumar Muthyala,
• Rainer Haag and
• Mathias Christmann

Beilstein J. Org. Chem. 2015, 11, 730–738, doi:10.3762/bjoc.11.83

• . Therefore, a constant number of catalytic units for each degree of functionalization was maintained. Initially, we decided to perform the reaction using trans-cinnamaldehyde (12) as a model substrate and trifluoroacetic acid (TFA) as an additive. In a preliminary survey on the water influence, a catalyst

Self-assembly of heteroleptic dinuclear metallosupramolecular kites from multivalent ligands via social self-sorting

• Christian Benkhäuser and
• Arne Lützen

Beilstein J. Org. Chem. 2015, 11, 693–700, doi:10.3762/bjoc.11.79

• (3, 1 g, 5.1 mmol) and paraformaldehyde (323 mg, 10.8 mmol, 2.1 equiv) were mixed in a round-bottomed flask in the dark and cooled with an ice bath. Trifluoroacetic acid (15.2 mL, 133.2 mmol, 26 equiv) was added and the resulting mixture was stirred for 18 h in the dark. After that time the reaction

Synthesis of tripodal catecholates and their immobilization on zinc oxide nanoparticles

• Franziska Klitsche,
• Julian Ramcke,
• Julia Migenda,
• Andreas Hensel,
• Tobias Vossmeyer,
• Horst Weller,
• Silvia Gross and
• Wolfgang Maison

Beilstein J. Org. Chem. 2015, 11, 678–686, doi:10.3762/bjoc.11.77

• = hydroxybenzotriazole; TFA = trifluoroacetic acid, KOTMS = potassium trimethylsilanolate, DIEA = N,N-diisopropylethylamine. Synthesis of tripodal catecholate platforms 11 and 13 for surface functionalization. Supporting Information Supporting Information File 192: Experimental procedures, additional analytical data

Synthesis of 1,2-cis-2-C-branched aryl-C-glucosides via desulfurization of carbohydrate based hemithioacetals

• Henok H. Kinfe,
• Fanuel M. Mebrahtu,
• Mandlenkosi M. Manana,
• Kagiso Madumo and
• Mokela S. Sokamisa

Beilstein J. Org. Chem. 2015, 11, 583–588, doi:10.3762/bjoc.11.64

• Hz coupling constants, respectively. The assignment of the glucoside 5a and mannoside 5a’ was based on a prolonged treatment of the aldehydic mixture with trifluoroacetic acid which effected no change in the ratio of the two epimers suggesting that it represents an equilibrium mixture. Consequently

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• crystalline hydrochloride salts may be precipitated directly from the medium in acylation reactions employing acyl chlorides. The eventual identification of anhydrous trifluoroacetic acid (CF3CO2H) as perhaps the most appropriate reaction medium identified so far for such acidic acylation reactions will

• -L-proline, L-serine, DL-serine and L-threonine were all obtained directly in excellent purity in over 90% yield at >10 g scale. Early O-acylation of hydroxyamino acids in trifluoroacetic acid As narrated in the previous section, developments taking place from the early 1940s into the early 1960s had

• eventually open up for just such a possibility. Trifluoroacetic acid (CF3CO2H) has been known since 1922 [21], but its widespread application was only made possible sometime later, much due to the development of electrochemical fluorination processes (Simons process) for production of organofluorine

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Efficient deprotection of F-BODIPY derivatives: removal of BF₂ using Brønsted acids

• Mingfeng Yu,
• Joseph K.-H. Wong,
• Cyril Tang,
• Peter Turner,
• Matthew H. Todd and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 37–41, doi:10.3762/bjoc.11.6

• 10.3762/bjoc.11.6 Abstract The effective and efficient removal of the BF2 moiety from F-BODIPY derivatives has been achieved using two common Brønsted acids; treatment with trifluoroacetic acid (TFA) or methanolic hydrogen chloride (HCl) followed by work-up with Ambersep® 900 resin (hydroxide form

• using two common Brønsted acids: treatment with trifluoroacetic acid (TFA) or methanolic hydrogen chloride (HCl) at room temperature followed by work-up with Ambersep® 900 resin (hydroxide form) achieves this conversion in near-quantitative yields. We have an ongoing interest in triazolyl-cyclam

Sequential decarboxylative azide–alkyne cycloaddition and dehydrogenative coupling reactions: one-pot synthesis of polycyclic fused triazoles

• Kuppusamy Bharathimohan,
• Thanasekaran Ponpandian,
• A. Jafar Ahamed and
• Nattamai Bhuvanesh

Beilstein J. Org. Chem. 2014, 10, 3031–3037, doi:10.3762/bjoc.10.321

• C–H bond in several C–H activation reactions [44][45][46][47][48]. Thus, the reaction was carried out with additives such as pivalic acid, acetic acid or trifluoroacetic acid in the above catalytic system (Table 1, entries 5–5b). When pivalic acid was used, the product formation was improved to 35

• % (Table 1, entry 5a) whereas acetic acid and trifluoroacetic acid conditions yielded 15% and 19% of 4a, respectively. None of these modifications provided the desired product in good yield. Therefore, finally we studied the effect of solvents on these reactions. Several polar and non-polar solvents such

(2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-Mono(di,tri)fluoromethylcyclopropyl]alanines and their incorporation into hormaomycin analogues

• Armin de Meijere,
• Sergei I. Kozhushkov,
• Dmitrii S. Yufit,
• Christian Grosse,
• Marcel Kaiser and
• Vitaly A. Raev

Beilstein J. Org. Chem. 2014, 10, 2844–2857, doi:10.3762/bjoc.10.302

• trifluoroacetic acid (Figure 6). Some antiparasitic activities of hormaomycin, its all-peptide analogue and the new analogues The syntheses of hormaomycin (1) itself and of its all-peptide aza-analogues 60 and 61 (Figure 6) as developed by Zlatopolskiy et al. [9][12], were reproduced in order to provide large

Solution processable diketopyrrolopyrrole (DPP) cored small molecules with BODIPY end groups as novel donors for organic solar cells

• Diego Cortizo-Lacalle,
• Calvyn T. Howells,
• Upendra K. Pandey,
• Joseph Cameron,
• Neil J. Findlay,
• Anto Regis Inigo,
• Tell Tuttle,
• Peter J. Skabara and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2683–2695, doi:10.3762/bjoc.10.283

• -dimethylformamide, rt, 16 h, 88%; (iii) trifluoroacetic acid, dichloromethane, rt, 16 h; DDQ, rt, 24 h; triethylamine, BF3·OEt2, rt, 24 h, 33% and 12% for 6 and 7, respectively; (iv) DPP 8, Pd2(dba)3, tri-tert-butylphosphonium tetrafluoroborate, THF/water, tripotassium phosphate, reflux, 48 h, 55% and 34% for 9 and

Synthesis of aromatic glycoconjugates. Building blocks for the construction of combinatorial glycopeptide libraries

• Markus Nörrlinger and
• Thomas Ziegler

Beilstein J. Org. Chem. 2014, 10, 2453–2460, doi:10.3762/bjoc.10.256

• also previously used for the preparation of a similar t-butyl succinate of glucosamine [25]. Upon treatment with trifluoroacetic acid in dichloromethane, esters 11 were converted into the corresponding free acids 12 in 91–98% yield (Table 1). Finally, glycopeptide building blocks 1 and 2 were prepared

A versatile δ-aminolevulinic acid (ΑLA)-cyclodextrin bimodal conjugate-prodrug for PDT applications with the help of intracellular chemistry

• Chrysie Aggelidou,
• Theodossis A. Theodossiou,
• Antonio Ricardo Gonçalves,
• Mariza Lampropoulou and
• Konstantina Yannakopoulou

Beilstein J. Org. Chem. 2014, 10, 2414–2420, doi:10.3762/bjoc.10.251

• conditions [(i) ΜeOH, Pd/C, H2, (ii) ΜeOH, formic acid, Pd/C, H2, (iii) ΜeOH, acetic acid, Pd/C, H2, (iv) ΜeOH, trifluoroacetic acid, Pd/C, H2]. A successful alternative was subsequently adopted comprising the linking of 4 to δ-azidolevulinic acid (8) (Scheme 2). The latter, having the nucleophilicity of the