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Search for "trifluoroacetic acid" in Full Text gives 274 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
β-Lactamase inhibition profile of new amidine-substituted diazabicyclooctanes
- Zafar Iqbal,
- Lijuan Zhai,
- Yuanyu Gao,
- Dong Tang,
- Xueqin Ma,
- Jinbo Ji,
- Jian Sun,
- Jingwen Ji,
- Yuanbai Liu,
- Rui Jiang,
- Yangxiu Mu,
- Lili He,
- Haikang Yang and
- Zhixiang Yang
Beilstein J. Org. Chem. 2021, 17, 711–718, doi:10.3762/bjoc.17.60
- deprotection was achieved by using trifluoroacetic acid (TFA) before the preparative HPLC. The synthesis of compounds A22 and A23 was accomplished by an alternative route elaborated in Scheme 5. Coupling of compound 5 and intermediate 2 was achieved by using HATU and DIPEA in a DMF/CH2Cl2 mixture to form the
Graphical Abstract
Scheme 1: Synthesis of intermediate 1. Reagents and conditions: (i) trifluoroacetic anhydride, CH2Cl2, 0–35 °...
Scheme 2: Synthesis of intermediate 2. Reagents and conditions: (i) Pd/C (wet), EtOAc/CH2Cl2, H2, 45 psi, rt,...
Scheme 3: Synthesis of intermediates 3–5. Reagents and conditions: (i) (Ac)2O, CH2Cl2, rt, 24 h, 95–99%; (ii)...
Scheme 4: Synthesis of compounds A1–21. Reagents and conditions: (i) acetyl chloride, TEA, CH2Cl2, rt, 16 h, ...
Scheme 5: Synthesis of compounds A22 and A23. Reagents and conditions: (i) HATU, DIPEA or DCC, DMAP, DMF or T...
Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting
- Masayori Hagimori,
- Estefanía E. Mendoza-Ortega and
- Marie Pierre Krafft
Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45
- ), piperidine, acetic anhydride, trifluoroacetic acid (TFA), triisopropylsilane (TIS), Rink Amide AM resin (4-(2’,4’-dimethoxyphenyl-Fmoc-aminomethyl)phenoxyacetamido-aminomethyl resin, 100–200 mesh), and Tube-O-DIALYZER™ mini dialysis system (MWCO 1K) from Merck (Darmstadt, Germany). 1,2
Graphical Abstract
Scheme 1: a) Schematic representation of a perfluorohexane-stabilized microbubble with a fluorinated lipopept...
Scheme 2: Solid-phase synthesis of F-lipopeptides 1–3 and hydrocarbon counterpart 4.
Figure 1: Adsorption kinetics of perfluoroalkylated lipopeptides 1–3 and the hydrocarbon analog 4 at the air/...
Figure 2: Adsorption of perfluoroalkylated lipopeptides 1–3 and hydrocarbon analog 4 on DPPC monolayers sprea...
Figure 3: Optical micrographs and corresponding size distribution of the perfluorohexane-stabilized microbubb...
Figure 4: Half-lives of microbubbles (25 °C) containing F-lipopeptides 1–3 and hydrocarbon analog 4.
Hydrazides in the reaction with hydroxypyrrolines: less nucleophilicity – more diversity
- Dmitrii A. Shabalin,
- Evgeniya E. Ivanova,
- Igor A. Ushakov,
- Elena Yu. Schmidt and
- Boris A. Trofimov
Beilstein J. Org. Chem. 2021, 17, 319–324, doi:10.3762/bjoc.17.29
- -pyrroline (1a) with an equimolar amount of benzohydrazide (2a) was initially performed in the presence of trifluoroacetic acid (TFA, 10 mol %) in refluxing acetonitrile for 3 h. Unexpectedly, 6-(2'-benzoylhydrazinyl)-1,4,5,6-tetrahydropyridazine 3aa was isolated in a 46% yield, while the anticipated 1,4
Graphical Abstract
Figure 1: Biologically active di- and tetrahydropyridazines.
Scheme 1: Recyclization of hydroxypyrrolines with hydrazine derivatives.
Scheme 2: Synthesis of tetrahydropyridazines 3.
Scheme 3: Synthesis of dihydropyridazines 4.
Scheme 4: Recyclization of hydroxypyrroline 1a with hydrazides 2d and 2e.
Scheme 5: A proposed mechanism for the recyclization of hydroxypyrrolines 1 with hydrazides 2.
Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring
- Daria I. Tonkoglazova,
- Anna V. Gulevskaya,
- Konstantin A. Chistyakov and
- Olga I. Askalepova
Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2
- acid as a cyclizing agent [72]. Unfortunately, only in the case of compound 9c, heating in trifluoroacetic acid led to isomerization into the required carbazole-based [6]helicene 10c (Table 5, entry 3). Under these conditions, alkynes 9a and 9b produced an unseparable mixture of some products. To our
- without THF solvent producing alkyne 9b in 82% yield (Table 4, entry 2). The structure of 9c was unambiguously proved by X-ray structural analysis (see Supporting Information File 1, Figure S34). Earlier, at the final step of a similar synthesis of the azine-fused [5]helicenes, we used trifluoroacetic
Graphical Abstract
Scheme 1: Overview of the synthetic methods for the carbazole-based heterohelicenes. i) Pd2dba3, xantphos, K3...
Scheme 2: Synthetic strategy for the carbazole-based [6]helicenes fused with an azine ring.
Scheme 3: Sonogashira coupling of compound 4b with phenylacetylene. i) Pd(PPh3)2Cl2, CuI, iPr2NH, DMSO, 80 °C...
Figure 1: Molecular structure of carbazole-based [6]helicenes 10a (a), 10b (b) and 10c (c) (X-ray data).
Figure 2: Crystal packing of carbazole-based [6]helicenes 10a (a, b), 10b (c,d) and 10c (e). Hydrogen atoms a...
Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom
- Giovanna Zanella,
- Martina Petrović,
- Dina Scarpi,
- Ernesto G. Occhiato and
- Enrique Gómez-Bengoa
Beilstein J. Org. Chem. 2020, 16, 3059–3068, doi:10.3762/bjoc.16.255
- ) [46]. The treatment of 11 with a catalytic amount of trifluoroacetic acid in toluene at 140 °C for 7 min led to the elimination of methanol and provided the 3-iodoenesulfonamide 12 in 77% yield [47]. To avoid the use of these harsh reaction conditions, we employed other methods, but both the
Graphical Abstract
Figure 1: Tandem acetate rearrangement/Nazarov cyclization of different substrates.
Figure 2: DFT-computed energy profile of the tandem Au(I)-catalyzed [3,3]-rearrangement/Nazarov reaction of 3...
Figure 3: DFT-computed energy profile of the tandem Au(I)-catalyzed [3,3]-rearrangement/Nazarov reaction of 2...
Figure 4: Computed comparison of the NBO charges of 2- and 3-substituted substrates.
Figure 5: Single-step transformation of IV to IX.
Figure 6: Triflate-promoted hydrogen abstraction and protodeauration with HOTf.
Figure 7: Triflate-mediated abstraction of the hydrogen atom Ha and protodeauration.
Scheme 1: Synthesis of the enynyl acetate starting material 14.
Scheme 2: Synthesis and cyclization of enynyl acetate 20.
Semiautomated glycoproteomics data analysis workflow for maximized glycopeptide identification and reliable quantification
- Steffen Lippold,
- Arnoud H. de Ru,
- Jan Nouta,
- Peter A. van Veelen,
- Magnus Palmblad,
- Manfred Wuhrer and
- Noortje de Haan
Beilstein J. Org. Chem. 2020, 16, 3038–3051, doi:10.3762/bjoc.16.253
- , capacity 8 g/L) were obtained from ThermoFisher Scientific (Leiden, Netherlands). All used chemicals were from Sigma-Aldrich (Zwijndrecht, Netherlands) except for trifluoroacetic acid (Merck, Darmstadt, Germany) and acetonitrile (Biosolve, Valkenswaard, Netherlands). Purified water was used from a Purelab
Graphical Abstract
Figure 1: Integration of automated glycopeptide identification by Byonic and GlycopeptideGraphMS (aided by Op...
Figure 2: Representative IgG and IgA glycopeptide clusters detected by GlycopeptideGraphMS.
Figure 3: Representative GlycopeptideGraphMS output for peptides of interest. Assigned compositions were iden...
Figure 4: Comparison of quantification results obtained by manual integration of EICs in Skyline (black), aut...
All-carbon [3 + 2] cycloaddition in natural product synthesis
- Zhuo Wang and
- Junyang Liu
Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251
- ). An intermolecular [3 + 2] cycloaddition of tetrasubstituted alkene 150 and the dhdt-2-methanol reagent 151 under the effect of trifluoroacetic acid produced adduct 154 in 52% yield. The authors identified that the cyclic nature of the dhdt-2-methanol reagent 151 is essential for the cycloaddition to
Graphical Abstract
Figure 1: Highly-substituted five-membered carbocycle in biologically significant natural products.
Figure 2: Natural product synthesis featuring the all-carbon [3 + 2] cycloaddition. (Quaternary carbon center...
Scheme 1: Representative natural product syntheses that feature the all-carbon [3 + 2] cyclization as the key...
Scheme 2: (A) An intramolecular trimethylenemethane diyl [3 + 2] cycloaddition with allenyl diazo compound 38...
Scheme 3: (A) Palladium-catalyzed intermolecular carboxylative TMM cycloaddition [36]. (B) The proposed mechanism....
Scheme 4: Natural product syntheses that make use of palladium-catalyzed intermolecular [3 + 2] cycloaddition...
Scheme 5: (A) Phosphine-catalyzed [3 + 2] cycloaddition [17]. (B) The proposed mechanism.
Scheme 6: Lu’s [3 + 2] cycloaddition in natural product synthesis. (A) Synthesis of longeracinphyllin A (10) [41]...
Scheme 7: (A) Phosphine-catalyzed [3 + 2] annulation of unsymmetric isoindigo 100 with allene in the preparat...
Scheme 8: (A) Rhodium-catalyzed intracmolecular [3 + 2] cycloaddition [49]. (B) The proposed catalytic cycle of t...
Scheme 9: Total synthesis of natural products reported by Yang and co-workers applying rhodium-catalyzed intr...
Scheme 10: (A) Platinum(II)-catalyzed intermolecular [3 + 2] cycloaddition of propargyl ether 139 and n-butyl ...
Scheme 11: (A) Platinum-catalyzed intramolecular [3 + 2] cycloaddition of propargylic ketal derivative 142 to ...
Scheme 12: (A) Synthesis of phyllocladanol (21) features a Lewis acid-catalyzed formal intramolecular [3 + 2] ...
Scheme 13: The recent advances of [3 + 2] annulation in natural product synthesis. (A) The preparation of melo...
Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of 1JC,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites
- Md. Rokon Ul Karim,
- Enjuro Harunari,
- Amit Raj Sharma,
- Naoya Oku,
- Kazuaki Akasaka,
- Daisuke Urabe,
- Mada Triandala Sibero and
- Yasuhiro Igarashi
Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222
- , and as expected, supplementation of a trace amount of trifluoroacetic acid (TFA) to DMSO-d6, combined with a longer relaxation delay (d1 = 30 s) for the 13C NMR experiment, greatly improved the detectability of sp2 carbon resonances. The 13C and HSQC spectra collected in this solvent mixture allowed
- Bruker AVANCE II 500 MHz NMR spectrometer in DMSO-d6 supplemented with a trace amount of trifluoroacetic acid using the signals of the residual solvent protons (δH 2.49) and carbon atoms (δC 39.5) as internal standards for compounds 1–5, or in CDCl3 using the signals of the residual solvent protons (δH
Graphical Abstract
Figure 1: Structure of the nocarimidazoles 1–4 and the bulbimidazoles 5–7.
Figure 2: COSY and key HMBC correlations for 1 and 2.
Scheme 1: Synthesis of the model compounds 8 and 9.
Figure 3: 1JC,H coupling constant for the imidazole ring of the natural products 1 and 5 and the model compou...
Figure 4: Determination of the absolute configuration of 1 (a), 4 (b), and 5 (c) by the Ohrui–Akasaka method.
Figure 5: Stereochemical diversity of the anteiso-chain chirality in microbial metabolites.
Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches
- Jannis Ludwig,
- Tobias Moje,
- Fynn Röhricht and
- Rainer Herges
Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210
- procedure of Nishimura et al. using mercury acetate in trifluoroacetic acid and anisole as radical scavenger (Scheme 5) [34]. Cleavage of the tert-butyl protection group yielded the disulfide 1g, which was reduced with catecholborane in tetrahydrofuran to give the free thiol 1h, which readily reoxidizes
Graphical Abstract
Figure 1: “Record player” approach for molecular spin switching. a) General principle b) Variation of the sub...
Scheme 1: Synthesis of the nitroso compounds 3 and 6 using the two different methods described by Wegner et a...
Scheme 2: Synthesis of azopyridines 11, 14, 16 and 18 by nucleophilic aromatic substitution.
Scheme 3: Synthesis of 3-(3-bromophenylazo)-4-cyanopyridine (20), which was hydrolyzed to yield 3-(3-bromophe...
Scheme 4: Modular approach for the C–C connection of the Ni(II)-porphyrin 22 and the different 4-substituted ...
Scheme 5: Cleavage of 1f to yield disulfide 1g [34].
Figure 2: Hammett plot of the investigated pyridine substituents [36].
Figure 3: UV–vis spectra of 1e (top), 1h (left) and 1j (right) in acetone water (1:9) (solid line) and after ...
Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties
- Anka Utama Putra,
- Deniz Çakmaz,
- Nurgül Seferoğlu,
- Alberto Barsella and
- Zeynel Seferoğlu
Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189
- donor than the phenol group [52][53]. Furthermore, trifluoroacetic acid (TFA) was added to a solution containing the deprotonated forms of dyes 8–12 in DMSO, so as to investigate the reversible protonation of the dyes. As can be seen in Figure 5, the addition of 5 equiv of TFA to a basic solution of 12
Graphical Abstract
Scheme 1: Synthetic pathways of dyes 3–7 and Schiff base analogs 8–12.
Figure 1: The optimized geometry of dyes 3 and 8.
Figure 2: Absorption spectra of dyes 3 (a, left) and 8 (b, right). Inset: Color of dyes 3 and 8 in the given ...
Figure 3: Emission spectra of dyes 3 (a, left) and 8 (b, right). Inset: Color of dyes 3 and 8 in the indicate...
Figure 4: Red shift phenomena with changing substituents in absorption (a, left) and emission (b, right) spec...
Figure 5: Absorption (a, left) and emission (b, right) change of dye 12 upon addition of 15 equiv of TBAOH an...
Figure 6: Photographs of dye 12 (left, ambient light), without, after the addition of 15 equiv of TBAOH (midd...
Figure 7: Absorption (a, left) and emission (b, right) change of 8 in Britton–Robinson buffer solutions at di...
Figure 8: Photographs of dye 8 in Britton–Robinson buffer solutions at different pH values.
Figure 9: Sigmoid function obtained from dye 8 UV–vis absorption spectra during pH investigation.
Figure 10: TGA curves of all synthetized dyes.
Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners
- Shakeel Alvi and
- Rashid Ali
Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186
- , they obtained o-bromohydroxysumanene 72 instead of 71. More interestingly, it was also noticed that by treating 71 with trifluoroacetic acid (TFA), it instantly transformed into sumanene derivative 72, suggesting that 71 is unstable under acidic conditions. The acid-catalyzed aromatization can be
Graphical Abstract
Figure 1: Representation of corannulene (1) and sumanene (2), the subunits of fullerene (C60).
Scheme 1: Mehta’s unsuccessful effort for the synthesis of sumanene scaffold 2.
Scheme 2: First synthesis of sumanene 2 by Sakurai et al. from norbornadiene 10.
Scheme 3: Synthesis of trimethylsumanene 28 from easily accessible norbornadiene (10).
Scheme 4: Generation of anions 29–31 and the preparation of tris(trimethylsilyl)sumanene 32.
Scheme 5: Synthesis of tri- and hexa-substituted sumanene derivatives.
Scheme 6: Synthesis of bowl-shaped π-extended sumanene derivatives 37a–f.
Scheme 7: Synthesis of monooxasumanene 38, trioxosumanene 40 along with imination of them.
Scheme 8: Synthesis of trimethylsumanenetrione 46 and exo-functionalized products 45a,b.
Scheme 9: Synthesis of bisumanenylidene 47 and sumanene dimer 48 from 2.
Scheme 10: The mono-substitution of 2 to generate diverse mono-sumanene derivatives 49a–d.
Scheme 11: Synthesis of sumanene building block 53 useful for further extension.
Scheme 12: Synthesis of hexafluorosumanene derivative 55 by Sakurai and co-workers.
Scheme 13: Preparation of sumanene-based carbene 60 and its reaction with cyclohexane.
Scheme 14: Barton–Kellogg reaction for the synthesis of sterically hindered alkenes.
Scheme 15: Synthesis of hydroxysumanene 68 by employing Baeyer–Villiger oxidation.
Scheme 16: Synthesis of sumanene derivatives having functionality at an internal carbon.
Scheme 17: Mechanism for nucleophilic substitution reaction at the internal carbon.
Scheme 18: Synthesis of diverse monosubstituted sumanene derivatives.
Scheme 19: Synthesis of di- and trisubstituted sumanene derivatives from sumanene (2).
Scheme 20: Preparation of monochlorosumanene 88 and hydrogenation of sumanene (2).
Scheme 21: The dimer 90 and bissumanenyl 92 achieved from halosumannes.
Scheme 22: Pyrenylsumanene 93 involving the Suzuki-coupling as a key transformation.
Scheme 23: Synthesis of various hexaarylsumanene derivatives using the Suzuki-coupling reaction.
Scheme 24: Synthesis of hexasubstituted sumanene derivatives 96 and 97.
Scheme 25: Synthesis of thioalkylsumanenes via an aromatic nucleophilic substitution reaction.
Scheme 26: Synthesis of tris(ethoxycarbonylethenyl)sumanene derivative 108.
Scheme 27: Synthesis of ferrocenyl-based sumanene derivatives.
Scheme 28: Synthesis of sumanenylferrocene architectures 118 and 119 via Negishi coupling.
Scheme 29: Diosmylation and the synthesis of phenylboronate ester 121 of sumanene.
Scheme 30: Synthesis of the iron-complex of sumanene.
Scheme 31: Synthesis of tri- and mononuclear sumanenyl zirconocene complexes.
Scheme 32: Synthesis of [CpRu(η6-sumanene)]PF6.
Scheme 33: Preparation of sumanene-based porous coordination networks 127 (spherical tetramer units) and 128 (...
Scheme 34: Synthesis of sumanenylhafnocene complexes 129 and 130.
Scheme 35: Synthesis of 134 and 135 along with PdII coordination complex 136.
Scheme 36: Synthesis of alkali metals sumanene complex K7(C21H102−)2(C21H93−)·8THF (137) containing di- and tr...
Scheme 37: The encapsulation of a Cs+ ion between two sumanenyl anions.
Scheme 38: Synthesis of monothiasumanene 140 and dithiasumanene 141 from 139.
Scheme 39: Synthesis of trithiasumanene 151 by Otsubo and his co-workers.
Scheme 40: Synthesis of trithiasumanene derivatives 155 and 156.
Scheme 41: Synthetic route towards hexathiolated trithiasumanenes 158.
Scheme 42: Synthesis of triselenasumanene 160 by Shao and teammates.
Scheme 43: Synthesis of tritellurasumanene derivatives from triphenylene skeletons.
Scheme 44: Synthesis of pyrazine-fused sumanene architectures through condensation reaction.
Scheme 45: Treatment of the trichalcogenasumanenes with diverse oxidative reagents.
Scheme 46: Ring-opening reaction with H2O2 and oxone of heterasumanenes 178 and 179.
Scheme 47: Synthesis of polycyclic compounds from sumanene derivatives.
Scheme 48: Synthesis of diimide-based heterocycles reported by Shao’s and co-workers.
Scheme 49: Synthesis of pristine trichalcogenasumanenes, 151, 205, and 206.
Scheme 50: Synthesis of trichalcogenasumanenes via hexaiodotriphenylene precursor 208.
Scheme 51: Synthesis of trisilasumanenes 214 and 215.
Scheme 52: Synthesis of trisilasumanene derivatives 218 and 219.
Scheme 53: Synthesis of novel trigermasumanene derivative 223.
Scheme 54: An attempt towards the synthesis of tristannasumanene derivative 228.
Scheme 55: Synthesis of triphosphasumanene trisulfide 232 from commercially available 229.
Scheme 56: The doping of sumanene derivatives with chalcogens (S, Se, Te) and phosphorus.
Scheme 57: Synthesis of heterasumanene containing three different heteroatoms.
Scheme 58: Synthesis of trichalcogenasumanene derivatives 240 and 179.
Scheme 59: Preparation of trichalcogenasumanenes 245 and 248.
Scheme 60: Design and synthesis of trichalcogenasumanene derivatives 252 and 178.
Scheme 61: Synthesis of spirosumanenes 264–269 and non-spiroheterasumanenes 258–263.
Scheme 62: Synthesis of sumanene-type hetero polycyclic compounds.
Scheme 63: Synthesis of triazasumanenes 288 and its sulfone congener 287.
Scheme 64: Synthesis of C3-symmetric chiral triaryltriazasumanenes via cross-coupling reaction.
Scheme 65: Synthesis of mononaphthosumanene 293 using Suzuki coupling as a key step.
Scheme 66: Synthesis of di- and trinaphthosumanene derivatives 302–304.
Scheme 67: Synthesis of hemifullerene skeletons by Hirao’s group.
Scheme 68: Design and construction of C70 fragment from a C60 sumanene fragment.
Naphthalene diimide bis-guanidinio-carbonyl-pyrrole as a pH-switchable threading DNA intercalator
- Poulami Jana,
- Filip Šupljika,
- Carsten Schmuck and
- Ivo Piantanida
Beilstein J. Org. Chem. 2020, 16, 2201–2211, doi:10.3762/bjoc.16.185
- adjacent amino groups (pH 7, green) and decorated by two GCP arms protonated at pH 5 (red; pH-switchable DNA groove binders). Synthesis of compound 4. Conditions: a) mono-N-Boc-ethylenediamine, DMF, 90 °C; b) i) trifluoroacetic acid (TFA)/CH2Cl2 1:1, ii) Fmoc-Lys(Boc)-OH, DIPEA, HCTU; c) i) TFA/CH2Cl2 1:1
Graphical Abstract
Scheme 1: DNA-targeting roles of the structural components incorporated in the design of the novel small mole...
Scheme 2: Synthesis of compound 4. Conditions: a) mono-N-Boc-ethylenediamine, DMF, 90 °C; b) i) trifluoroacet...
Figure 1: UV–vis titrations of compound 4 (c = 1.0 × 10−6 M), with ct-DNA at pH 7.0 (a) and at pH 5 (b). Inse...
Figure 2: a) CD titration of ct-DNA (c = 3.0 × 10−5 M) with compound 4 at pH 7.0 (Na cacodylate buffer, I = 0...
Figure 3: CD titration of poly(rA)–poly(rU) (c = 3.0 × 10−5 M) with compound 4 at a) pH 7.0 (Na cacodylate bu...
Figure 4: CD titration of ds-DNAs (c = 3.0 × 10−5 M) with 4 for ratio r[4]/ [DNA] = 0.4. Done at pH 5.0 (Na c...
Figure 5: ITC experiments of poly(dAdT)–poly(dAdT) (c = 5.0 × 10−5 M) titrated with compound 4. Dots represen...
Figure 6: AFM image of a) ct-DNA showing a fibre-like structure with a length of several micrometres; b) upon...
Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate
- Mysore Bhyrappa Harisha,
- Pandi Dhanalakshmi,
- Rajendran Suresh,
- Raju Ranjith Kumar and
- Shanmugam Muthusubramanian
Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178
- -azirine, an efficient source of nitrogen, was employed as starting material for the synthesis of oxazole with various coupling partners such as aldehyde, trifluoroacetic acid, etc. [8][45][46][47][48][49][50] (Scheme 1). Thiazole is a common structural motif that is found in a wide variety of naturally
Graphical Abstract
Figure 1: Examples of biologically active oxazole and aminothiazole scaffolds.
Scheme 1: Strategies for the synthesis of 2,4,5-trisubstituted oxazole from azirine. a) I2, PPh3; b) NaH, 1H-...
Scheme 2: Scope of the α-azidochalcones. The reactions were carried out at reflux temperature, using 1 (1 mmo...
Scheme 3: Large-scale synthesis of 3i.
Figure 2: Large-scale synthesis of 3i. a) At the start of the reaction, b) after the reaction.
Scheme 4: Acetyl derivative of 3d.
Figure 3: ORTEP diagram of compound 5.
Scheme 5: Synthesis of S-methyl/benzylated products 6 and 7.
Scheme 6: Control experiments.
Scheme 7: Plausible mechanism proposed for the formation of 2,4,5-trisubstituted oxazoles 3.
Scheme 8: Reaction of vinyl azide 1 and 3 with ferric nitrate. Reactions were carried out at reflux temperatu...
Figure 4: X-ray crystal structure of 4h.
On the hydrolysis of diethyl 2-(perfluorophenyl)malonate
- Ilya V. Taydakov and
- Mikhail A. Kiskin
Beilstein J. Org. Chem. 2020, 16, 1863–1868, doi:10.3762/bjoc.16.153
- of diethyl 2-(perfluorophenyl)malonate, acid-catalyzed reactions were also tested. Trifluoroacetic acid (TFA) is a common reagent for the catalytic cleavage of tert-butyl esters, but in the stoichiometric quantity it is also suitable for the cleavage of nonvolatile methyl or ethyl esters due to
Graphical Abstract
Figure 1: Phenylmalonic acids.
Scheme 1: Synthesis of diethyl 2-phenylmalonate (4).
Scheme 2: Synthesis of diethyl 2-(perfluorophenyl)malonate (3).
Figure 2: Esters of fluorine-substituted 2-phenylmalonic acids.
Scheme 3: Hydrolysis of diethyl 2-(perfluorophenyl)malonate (3).
Figure 3: Molecular structure of 2-(perfluorophenyl)acetic acid (12).
Scheme 4: Formation of 2-(perfluorophenyl)acetic acid (12).
One-pot synthesis of isosorbide from cellulose or lignocellulosic biomass: a challenge?
- Isaline Bonnin,
- Raphaël Mereau,
- Thierry Tassaing and
- Karine De Oliveira Vigier
Beilstein J. Org. Chem. 2020, 16, 1713–1721, doi:10.3762/bjoc.16.143
- hydrolysis of cellulose and dehydration of sorbitol and sorbitans was studied and their efficiency decreased in the order of H2SO4 > triflic acid (HOTf) > trifluoroacetic acid (TFA) > Amberlyst-38 > HCl > HNO3. It was shown that when MCC was used as starting material, in the presence of Ru/C and H2SO4, 50
Graphical Abstract
Scheme 1: Conversion of cellulose to isosorbide.
Scheme 2: Combination of mineral acids or heteropolyacids and a supported metal catalyst to produce isosorbid...
Scheme 3: Conversion of sorbitol to isosorbide via the formation of sorbitans.
Scheme 4: Conversion of cellulose to isosorbide in the presence of heteropolyacids and metal-supported cataly...
Scheme 5: Summary of the results obtained in one-pot one step processes [21-25].
Scheme 6: Conversion of (ligno)cellulose to isosorbide in the presence of Amberlyt 70 and a Ru/C catalyst [26,27].
Scheme 7: Use of Ru-supported on mesoporous nobium phosphate (mNbPO) for the synthesis of isosorbide from cel...
Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study
- Csilla Hargitai,
- Györgyi Koványi-Lax,
- Tamás Nagy,
- Péter Ábrányi-Balogh,
- András Dancsó,
- Gábor Tóth,
- Judit Halász,
- Angéla Pandur,
- Gyula Simig and
- Balázs Volk
Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136
- ; ring-chain tautomerism; Introduction In a preliminary publication [1] we disclosed that methylenedioxy-substituted o-(pivaloylaminomethyl)benzaldehyde (1a), when kept in dichloromethane (DCM) in the presence of a catalytic amount (0.13 equiv) of trifluoroacetic acid (TFA) for 72 h at room temperature
- ,S)-2-(2,2-Dimethylpropanoyl)-2,3-dihydro-1H-isoindol-1-yl](2-formylphenyl)methyl]-2,2-dimethylpropanamide (23a). Method A: This compound was prepared according to general procedure I using 1e (1.01 g, 4.61 mmol) and trifluoroacetic acid (35 µL, 53 mg, 0.46 mmol). The title compound (584 mg, 58%) was
Graphical Abstract
Scheme 1: Rearrangement of methylenedioxy-substituted aminoaldehyde 1a to regioisomer 2a and formation of the...
Scheme 2: Synthesis of 1-arylisoindoles 6 and formation of dimers 5.
Scheme 3: Rearrangement of aminoaldehydes 1 to regioisomers 2 and formation of dimer-like products 3 and 8.
Figure 1: X-ray structures of compounds 3b (left) and 8b (right).
Scheme 4: Proposed mechanism of the isomerization of aldehydes 1 via isoindoles 4.
Scheme 5: Proposed mechanism of the formation of dimer-like products 3a,b.
Scheme 6: Proposed mechanism for the formation of dimer-like products 8a,b.
Scheme 7: Dimerization of indole under acidic conditions.
Figure 2: Gibbs free energy diagram for the 1→2 rearrangement.
Scheme 8: Reaction of o-(pivaloylaminomethyl)benzaldehyde (1e) to give dimer-like products 23a and 23b.
Figure 3: X-ray structures of compounds 23a (left) and 23b (right).
Figure 4: Structures of the minimal energy conformer of stereoisomer 23a and those of two minimal energy conf...
Heterogeneous photocatalysis in flow chemical reactors
- Christopher G. Thomson,
- Ai-Lan Lee and
- Filipe Vilela
Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125
Graphical Abstract
Figure 1: A) Bar chart of the publications per year for the topics “Photocatalysis” (49,662 instances) and “P...
Figure 2: A) Professor Giacomo Ciamician and Dr. Paolo Silber on their roof laboratory at the University of B...
Scheme 1: PRC trifluoromethylation of N-methylpyrrole (1) using hazardous gaseous CF3I safely in a flow react...
Figure 3: A) Unit cells of the three most common crystal structures of TiO2: rutile, brookite, and anatase. R...
Figure 4: Illustration of the key semiconductor photocatalysis events: 1) A photon with a frequency exceeding...
Figure 5: Photocatalytic splitting of water by oxygen vacancies on a TiO2(110) surface. Reprinted with permis...
Figure 6: Proposed adsorption modes of A) benzene, B) chlorobenzene, C) toluene, D) phenol, E) anisole, and F...
Figure 7: Structures of the sulfonate-containing organic dyes RB5 (3) and MX-5B (4) and the adsorption isothe...
Figure 8: Idealised triclinic unit cell of a g-C3N4 type polymer, displaying possible hopping transport scena...
Figure 9: Idealised structure of a perfect g-C3N4 sheet. The central unit highlighted in red represents one t...
Figure 10: Timeline of the key processes of charge transport following the photoexcitation of g-C3N4, leading ...
Scheme 2: Photocatalytic bifunctionalisation of heteroarenes using mpg-C3N4, with the selected examples 5 and ...
Figure 11: A) Structure of four linear conjugated polymer photocatalysts for hydrogen evolution, displaying th...
Figure 12: Graphical representation of the common methods used to immobilise molecular photocatalysts (PC) ont...
Figure 13: Wireless light emitter-supported TiO2 (TiO2@WLE) HPCat spheres powered by resonant inductive coupli...
Figure 14: Graphical representation of zinc–perylene diimide (Zn-PDI) supramolecular assembly photocatalysis v...
Scheme 3: Upconversion of NIR photons to the UV frequency by NaYF4:Yb,Tm nanocrystals sequentially coated wit...
Figure 15: Types of reactors employed in heterogeneous photocatalysis in flow. A) Fixed bed reactors and the s...
Figure 16: Electrochemical potential of common semiconductor, transition metal, and organic dye-based photocat...
Scheme 4: Possible mechanisms of an immobilised molecular photoredox catalyst by oxidative or reductive quenc...
Scheme 5: Scheme of the CMB-C3N4 photocatalytic decarboxylative fluorination of aryloxyacetic acids, with the...
Scheme 6: Scheme of the g-C3N4 photocatalytic desilylative coupling reaction in flow and proposed mechanism [208].
Scheme 7: Proposed mechanism of the radical cyclisation of unsaturated alkyl 2-bromo-1,3-dicarbonyl compounds...
Scheme 8: N-alkylation of benzylamine and schematic of the TiO2-coated microfluidic device [213].
Scheme 9: Proposed mechanism of the Pt@TiO2 photocatalytic deaminitive cyclisation of ʟ-lysine (23) to ʟ-pipe...
Scheme 10: A) Proposed mechanism for the photocatalytic oxidation of phenylboronic acid (24). B) Photos and SE...
Scheme 11: Proposed mechanism for the DA-CMP3 photocatalytic aza-Henry reaction performed in a continuous flow...
Scheme 12: Proposed mechanism for the formation of the cyclic product 32 by TiO2-NC HPCats in a slurry flow re...
Scheme 13: Reaction scheme for the photocatalytic synthesis of homo and hetero disulfides in flow and scope of...
Scheme 14: Reaction scheme for the MoOx/TiO2 HPCat oxidation of cyclohexane (34) to benzene. The graph shows t...
Scheme 15: Proposed mechanism of the TiO2 HPC heteroarene C–H functionalisation via aryl radicals generated fr...
Scheme 16: Scheme of the oxidative coupling of benzylamines with the HOTT-HATN HPCat and selected examples of ...
Scheme 17: Photocatalysis oxidation of benzyl alcohol (40) to benzaldehyde (41) in a microflow reactor coated ...
Figure 17: Mechanisms of Dexter and Forster energy transfer.
Scheme 18: Continuous flow process for the isomerisation of alkenes with an ionic liquid-immobilised photocata...
Scheme 19: Singlet oxygen synthetic step in the total synthesis of canataxpropellane [265].
Scheme 20: Scheme and proposed mechanism of the singlet oxygen photosensitisation by CMP_X HPCats, with the st...
Scheme 21: Structures of CMP HPCat materials applied by Vilela and co-workers for the singlet oxygen photosens...
Scheme 22: Polyvinylchloride resin-supported TDCPP photosensitisers applied for singlet oxygen photosensitisat...
Scheme 23: Structure of the ionically immobilised TPP photosensitiser on amberlyst-15 ion exchange resins (TPP...
Scheme 24: Photosensitised singlet oxygen oxidation of citronellol (46) in scCO2, with automatic phase separat...
Scheme 25: Schematic of PS-Est-BDP-Cl2 being applied for singlet oxygen photosensitisation in flow. A) Pseudo-...
Scheme 26: Reaction scheme of the singlet oxygen oxidation of furoic acid (54) using a 3D-printed microfluidic...
Figure 18: A) Photocatalytic bactericidal mechanism by ROS oxidative cleavage of membrane lipids (R = H, amino...
Figure 19: A) Suggested mechanisms for the aqueous pollutant degradation by TiO2 in a slurry flow reactor [284-287]. B)...
Figure 20: Schematic of the flow system used for the degradation of aqueous oxytetracycline (56) solutions [215]. M...
Scheme 27: Degradation of a salicylic acid (57) solution by a coupled solar photoelectro-Fenton (SPEF) process...
Figure 21: A) Schematic flow diagram using the TiO2-coated NETmix microfluidic device for an efficient mass tr...
Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore
- Esteban P. Urriolabeitia,
- Pablo Sánchez,
- Alexandra Pop,
- Cristian Silvestru,
- Eduardo Laga,
- Ana I. Jiménez and
- Carlos Cativiela
Beilstein J. Org. Chem. 2020, 16, 1111–1123, doi:10.3762/bjoc.16.98
- . The resulting reddish solid was filtered off, washed with additional portions of distilled water until the smell of the trifluoroacetic acid disappeared (in general 3 × 10 mL was sufficient, but a larger amount could be necessary), dried in vacuo and characterized as the orthopalladated dimers 3a–f
Graphical Abstract
Figure 1: (a) General scheme for truxillic acid derivatives; (b) general scheme for symmetric 1,3-diaminotrux...
Figure 2: (a) (Z)-4-Arylidene-2-aryl-5(4H)-oxazolones used for the synthesis of 1,3-diaminotruxillic derivati...
Figure 3: (Z)-4-Arylidene-2((E)-styryl)-5(4H)-oxazolones 2a–j used in this work and overall reaction scheme.
Figure 4: Molecular drawing of the oxazolone 2c.
Scheme 1: Ortho-palladation of oxazolones 2 by treatment with Pd(OAc)2 and different structures obtained for ...
Scheme 2: [2 + 2] Photocycloaddition of cyclopalladated complexes 3 in solution to give the dinuclear cyclobu...
Figure 5: Molecular drawing of cyclobutane ortho-palladated 4a. Ellipsoids are shown at the 50% probability l...
Scheme 3: Release of the 1,3-diaminotruxillic bis-amino ester derivatives 5 by methoxycarbonylation of the Pd...
Fluorinated phenylalanines: synthesis and pharmaceutical applications
- Laila F. Awad and
- Mohammed Salah Ayoup
Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91
- selective enzymatic hydrolysis of 64 using an acylase under mild conditions (pH 8.0, 40 °C, 4 d, with CoCl2 as co-factor) [51] (Scheme 14). 1.5. Direct radiofluorination of ʟ-phenylalanine The direct radiofluorination of ʟ-phenylalanine (66) with either [18F]F2 or [18F]AcOF in trifluoroacetic acid (TFA
Graphical Abstract
Figure 1: Categories I–V of fluorinated phenylalanines.
Scheme 1: Synthesis of fluorinated phenylalanines via Jackson’s method.
Scheme 2: Synthesis of all-cis-tetrafluorocyclohexylphenylalanines.
Scheme 3: Synthesis of ʟ-4-[sulfono(difluoromethyl)]phenylalanine (nPt: neopentyl, TCE: trichloroethyl).
Scheme 4: Synthesis of ʟ-4-[sulfono(difluoromethyl)]phenylalanine derivatives 17.
Scheme 5: Synthesis of fluorinated Phe analogues from Cbz-protected aminomalonates.
Scheme 6: Synthesis of tetrafluorophenylalanine analogues via the 3-methyl-4-imidazolidinone auxiliary 25.
Scheme 7: Synthesis of tetrafluoro-Phe derivatives via chiral auxiliary 31.
Scheme 8: Synthesis of 2,5-difluoro-Phe and 2,4,5-trifluoro-Phe via Schöllkopf reagent 34.
Scheme 9: Synthesis of 2-fluoro- and 2,6-difluoro Fmoc-Phe derivatives starting from chiral auxiliary 39.
Scheme 10: Synthesis of 2-[18F]FPhe via chiral auxiliary 43.
Scheme 11: Synthesis of FPhe 49a via photooxidative cyanation.
Scheme 12: Synthesis of FPhe derivatives via Erlenmeyer azalactone synthesis.
Scheme 13: Synthesis of (R)- and (S)-2,5-difluoro Phe via the azalactone method.
Scheme 14: Synthesis of 3-bromo-4-fluoro-(S)-Phe (65).
Scheme 15: Synthesis of [18F]FPhe via radiofluorination of phenylalanine with [18F]F2 or [18F]AcOF.
Scheme 16: Synthesis of 4-borono-2-[18F]FPhe.
Scheme 17: Synthesis of protected 4-[18F]FPhe via arylstannane derivatives.
Scheme 18: Synthesis of FPhe derivatives via intermediate imine formation.
Scheme 19: Synthesis of FPhe derivatives via Knoevenagel condensation.
Scheme 20: Synthesis of FPhe derivatives 88a,b from aspartic acid derivatives.
Scheme 21: Synthesis of 2-(2-fluoroethyl)phenylalanine derivatives 93 and 95.
Scheme 22: Synthesis of FPhe derivatives via Zn2+ complexes.
Scheme 23: Synthesis of FPhe derivatives via Ni2+ complexes.
Scheme 24: Synthesis of 3,4,5-trifluorophenylalanine hydrochloride (109).
Scheme 25: Synthesis of FPhe derivatives via phenylalanine aminomutase (PAM).
Scheme 26: Synthesis of (R)-2,5-difluorophenylalanine 115.
Scheme 27: Synthesis of β-fluorophenylalanine via 2-amino-1,3-diol derivatives.
Scheme 28: Synthesis of β-fluorophenylalanine derivatives via the oxazolidinone chiral auxiliary 122.
Scheme 29: Synthesis of β-fluorophenylalanine from pyruvate hemiketal 130.
Scheme 30: Synthesis of β-fluorophenylalanine (136) via fluorination of β-hydroxyphenylalanine (137).
Scheme 31: Synthesis of β-fluorophenylalanine from aziridine derivatives.
Scheme 32: Synthesis of β-fluorophenylalanine 136 via direct fluorination of pyruvate esters.
Scheme 33: Synthesis of β-fluorophenylalanine via fluorination of ethyl 3-phenylpyruvate enol using DAST.
Scheme 34: Synthesis of β-fluorophenylalanine derivatives using photosensitizer TCB.
Scheme 35: Synthesis of β-fluorophenylalanine derivatives using Selectflour and dibenzosuberenone.
Scheme 36: Synthesis of protected β-fluorophenylalanine via aziridinium intermediate 150.
Scheme 37: Synthesis of β-fluorophenylalanine derivatives via fluorination of α-hydroxy-β-aminophenylalanine d...
Scheme 38: Synthesis of β-fluorophenylalanine derivatives from α- or β-hydroxy esters 152a and 155.
Scheme 39: Synthesis of a series of β-fluoro-Phe derivatives via Pd-catalyzed direct fluorination of β-methyle...
Scheme 40: Synthesis of series of β-fluorinated Phe derivatives using quinoline-based ligand 162 in the Pd-cat...
Scheme 41: Synthesis of β,β-difluorophenylalanine derivatives from 2,2-difluoroacetaldehyde derivatives 164a,b....
Scheme 42: Synthesis of β,β-difluorophenylalanine derivatives via an imine chiral auxiliary.
Scheme 43: Synthesis of α-fluorophenylalanine derivatives via direct fluorination of protected Phe 174.
Figure 2: Structures of PET radiotracers of 18FPhe derivatives.
Figure 3: Structures of melfufen (179) and melphalan (180) anticancer drugs.
Figure 4: Structure of gastrazole (JB95008, 181), a CCK2 receptor antagonist.
Figure 5: Dual CCK1/CCK2 antagonist 182.
Figure 6: Structure of sitagliptin (183), an antidiabetic drug.
Figure 7: Structure of retaglpitin (184) and antidiabetic drug.
Figure 8: Structure of evogliptin (185), an antidiabetic drug.
Figure 9: Structure of LY2497282 (186) a DPP-4 inhibitor for the treatment of type II diabetes.
Figure 10: Structure of ulimorelin (187).
Figure 11: Structure of GLP1R (188).
Figure 12: Structures of Nav1.7 blockers 189 and 190.
Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches
- Rodrigo Costa e Silva,
- Luely Oliveira da Silva,
- Aloisio de Andrade Bartolomeu,
- Timothy John Brocksom and
- Kleber Thiago de Oliveira
Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83
- contains both the substrate (dihydroartemisinic acid) and the photocatalyst (chlorophyll a). The combination of the extract with trifluoroacetic acid promptly furnishes artemisinin, under continuous-flow conditions (3 min) using red light (87% yield) or under blue light irradiation (5 min, 88% yield
Graphical Abstract
Figure 1: Chemical structures of the porphyrinoids and their absorption spectra: in bold are highlighted the ...
Figure 2: Photophysical and photochemical processes (Por = porphyrin). Adapted from [12,18].
Figure 3: Main dual photocatalysts and their oxidative/reductive excited state potentials, including porphyri...
Scheme 1: Photoredox alkylation of aldehydes with diazo acetates using porphyrins and a Ru complex. aUsing a ...
Scheme 2: Proposed mechanism for the alkylation of aldehydes with diazo acetates in the presence of TPP.
Scheme 3: Arylation of heteroarenes with aryldiazonium salts using TPFPP as photocatalyst, and corresponding ...
Scheme 4: A) Scope with different aryldiazonium salts and enol acetates. B) Photocatalytic cycles and compari...
Scheme 5: Photoarylation of isopropenyl acetate A) Comparison between batch and continuous-flow approaches an...
Scheme 6: Dehalogenation induced by red light using thiaporphyrin (STPP).
Scheme 7: Applications of NiTPP as both photoreductant and photooxidant.
Scheme 8: Proposed mechanism for obtaining tetrahydroquinolines by reductive quenching.
Scheme 9: Selenylation and thiolation of anilines.
Scheme 10: NiTPP as photoredox catalyst in oxidative and reductive quenching, in comparison with other photoca...
Scheme 11: C–O bond cleavage of 1-phenylethanol using a cobalt porphyrin (CoTMPP) under visible light.
Scheme 12: Hydration of terminal alkynes by RhIII(TSPP) under visible light irradiation.
Scheme 13: Regioselective photocatalytic hydro-defluorination of perfluoroarenes by RhIII(TSPP).
Scheme 14: Formation of 2-methyl-2,3-dihydrobenzofuran by intramolecular hydro-functionalization of allylpheno...
Scheme 15: Photocatalytic oxidative hydroxylation of arylboronic acids using UNLPF-12 as heterogeneous photoca...
Scheme 16: Photocatalytic oxidative hydroxylation of arylboronic acids using MOF-525 as heterogeneous photocat...
Scheme 17: Preparation of the heterogeneous photocatalyst CNH.
Scheme 18: Photoinduced sulfonation of alkenes with sulfinic acid using CNH as photocatalyst.
Scheme 19: Sulfonic acid scope of the sulfonation reactions.
Scheme 20: Regioselective sulfonation reaction of arimistane.
Scheme 21: Synthesis of quinazolin-4-(3H)-ones.
Scheme 22: Selective photooxidation of aromatic benzyl alcohols to benzaldehydes using Pt/PCN-224(Zn).
Scheme 23: Photooxidation of benzaldehydes to benzoic acids using Pt or Pd porphyrins.
Scheme 24: Photocatalytic reduction of various nitroaromatics using a Ni-MOF.
Scheme 25: Photoinduced cycloadditions of CO2 with epoxides by MOF1.
Figure 4: Electronic configurations of the species of oxygen. Adapted from [66].
Scheme 26: TPP-photocatalyzed generation of 1O2 and its application in organic synthesis. Adapted from [67-69].
Scheme 27: Pericyclic reactions involving singlet oxygen and their mechanisms. Adapted from [67].
Scheme 28: First scaled up ascaridole preparation from α-terpinene.
Scheme 29: Antimalarial drug synthesis using an endoperoxidation approach.
Scheme 30: Photooxygenation of colchicine.
Scheme 31: Synthesis of (−)-pinocarvone from abundant (+)-α-pinene.
Scheme 32: Seeberger’s semi-synthesis of artemisinin.
Scheme 33: Synthesis of artemisinin using TPP and supercritical CO2.
Scheme 34: Synthesis of artemisinin using chlorophyll a.
Scheme 35: Quercitol stereoisomer preparation.
Scheme 36: Photocatalyzed preparation of naphthoquinones.
Scheme 37: Continuous endoperoxidation of conjugated dienes and subsequent rearrangements leading to oxidized ...
Scheme 38: The Opatz group total synthesis of (–)-oxycodone.
Scheme 39: Biomimetic syntheses of rhodonoids A, B, E, and F.
Scheme 40: α-Photooxygenation of chiral aldehydes.
Scheme 41: Asymmetric photooxidation of indanone β-keto esters by singlet oxygen using PTC as a chiral inducer...
Scheme 42: Asymmetric photooxidation of both β-keto esters and β-keto amides by singlet oxygen using PTC-2 as ...
Scheme 43: Bifunctional photo-organocatalyst used for the asymmetric oxidation of β-keto esters and β-keto ami...
Scheme 44: Mechanism of singlet oxygen oxidation of sulfides to sulfoxides.
Scheme 45: Controlled oxidation of sulfides to sulfoxides using protonated porphyrins as photocatalysts. aIsol...
Scheme 46: Photochemical oxidation of sulfides to sulfoxides using PdTPFPP as photocatalyst.
Scheme 47: Controlled oxidation of sulfides to sulfoxides using SnPor@PAF as a photosensitizer.
Scheme 48: Syntheses of 2D-PdPor-COF and 3D-Pd-COF.
Scheme 49: Photocatalytic oxidation of A) thioanisole to methyl phenyl sulfoxide and B) various aryl sulfides,...
Scheme 50: General mechanism for oxidation of amines to imines.
Scheme 51: Oxidation of secondary amines to imines.
Scheme 52: Oxidation of secondary amines using Pd-TPFPP as photocatalyst.
Scheme 53: Oxidative amine coupling using UNLPF-12 as heterogeneous photocatalyst.
Scheme 54: Synthesis of Por-COF-1 and Por-COF-2.
Scheme 55: Photocatalytic oxidation of amines to imines by Por-COF-2.
Scheme 56: Photocyanation of primary amines.
Scheme 57: Synthesis of ᴅ,ʟ-tert-leucine hydrochloride.
Scheme 58: Photocyanation of catharanthine and 16-O-acetylvindoline using TPP.
Scheme 59: Photochemical α-functionalization of N-aryltetrahydroisoquinolines using Pd-TPFPP as photocatalyst.
Scheme 60: Ugi-type reaction with 1,2,3,4-tetrahydroisoquinoline using molecular oxygen and TPP.
Scheme 61: Ugi-type reaction with dibenzylamines using molecular oxygen and TPP.
Scheme 62: Mannich-type reaction of tertiary amines using PdTPFPP as photocatalyst.
Scheme 63: Oxidative Mannich reaction using UNLPF-12 as heterogeneous photocatalyst.
Scheme 64: Transformation of amines to α-cyanoepoxides and the proposed mechanism.
Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides
- Péter Bagi,
- Réka Herbay,
- Nikolett Péczka,
- Zoltán Mucsi,
- István Timári and
- György Keglevich
Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75
- trifluoroacetic acid, a mixture containing the corresponding 2- and 3-phospholene oxides (4a and 1a) in a ratio of 11:89 was obtained. However, when phospholene oxide 1a was heated in neat methanesulfonic acid at 160 °C for 24 h, 4a and 1a in a ratio of 97:3 were obtained, but the yield of the mixture was 57% due
Graphical Abstract
Figure 1: Examples for catalytically or biologically active molecules containing five-membered P-heterocyclic...
Scheme 1: Comparison of the isomerization of 1-phenyl-3-phospholene oxide (5), 1-phenyl-3-methyl-3-phospholen...
Scheme 2: Three possible reaction mechanisms considered in the theoretical studies for the isomerization of 3...
Figure 2: The full time experimental kinetic curves (a); The initial part of the kinetic curves of 1c–f and 1h...
Scheme 3: Computed reaction mechanism of the 3-phospholene oxide (1) 2-phospholene oxide (4) isomerization un...
Scheme 4: Computed reaction mechanism of the 3-phospholene oxide (1) 2-phospholene oxide (4) isomerization un...
Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid
- Dong Cai,
- ZhiHua Zhang,
- Yufan Meng,
- KaiLi Zhu,
- LiYi Chen,
- ChangXiang Yu,
- ChangWei Yu,
- ZiYi Fu,
- DianShen Yang and
- YiXia Gong
Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73
- based on the reaction of carboxylic acid with N-Boc-protected aliphatic diamine in the presence of activators and then deprotection of the tert‐butoxycarbonyl (Boc) group using trifluoroacetic acid (TFA) [20]. Compared with the mentioned methods, the latter method achieves the higher yield (up to 90
- factor is that the acidity of chloroacetic acid (pKa = 2.87) was stronger than that of acetic acid (pKa = 4.76). The procedure for the generation of byproduct 11 was similar to N-Boc-deprotection using trifluoroacetic acid. The effective synthesis of compound 10 was then explored (Table 3). In our
Graphical Abstract
Figure 1: Chemical structure of 18β-glycyrrhetinic acid and known derivatives.
Scheme 1: Synthesis of compound 4. Reagents and conditions: (a) Ac2O, NEt3, DMF (cat.), DCM, 25 °C, 1 day; (b...
Scheme 2: Synthesis of compound 4. Reagents and conditions: (a) Ac2O, 130 °C, 1 h; (b) 1-Boc-piperazine, CH3C...
Figure 2: a) Estimated structure of the intermediate 6; b) Possible aminolysis process.
Scheme 3: Synthesis of byproduct 11. Reagents and conditions: (a) chloroacetic anhydride, 130 °C, 1 h.
Scheme 4: Synthesis of compound 17. Reagents and conditions: (a) chloroacetic anhydride, 130 °C, 1 h; (b) mor...
Figure 3: Crystal structure of conpound 18.
Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization
- Valentina A. Ol’shevskaya,
- Elena G. Kononova and
- Andrei V. Zaitsev
Beilstein J. Org. Chem. 2019, 15, 2704–2709, doi:10.3762/bjoc.15.263
- porphyrin 4a with maleic anhydride by analogy with a well-known standard procedure [39][40] provided the target maleimide-substituted porphyrin 5a in 42% yield, which contains four maleimide moieties in the structure. Treatment of porphyrin 5a with trifluoroacetic acid in CHCl3 resulted in the removal of
Graphical Abstract
Scheme 1: Synthesis of fluorinated maleimide-substituted porphyrins 5a, 6, 7a, 7b, and 8.
Scheme 2: Synthesis of fluorinated maleimide-substituted chlorins 12,13.
Synthesis of novel sulfide-based cyclic peptidomimetic analogues to solonamides
- José Brango-Vanegas,
- Luan A. Martinho,
- Lucinda J. Bessa,
- Andreanne G. Vasconcelos,
- Alexandra Plácido,
- Alex L. Pereira,
- José R. S. A. Leite and
- Angelo H. L. Machado
Beilstein J. Org. Chem. 2019, 15, 2544–2551, doi:10.3762/bjoc.15.247
- anhydride to yield 7. Despite the good results for the acetylation of peptides 6 with R = Me at room temperature, the reaction of the ones with R = n-hexyl needed to be conducted under heat conditions (50 °C). Acidic treatment of the acetates 7 with trifluoroacetic acid: triisopropylsilane decoupling
Graphical Abstract
Figure 1: Chemical structure of solonamides and autoinducing peptides (AIP).
Scheme 1: Macrocyclization strategy based on SN2’.
Scheme 2: Chemical synthesis of the MBH adducts 2 and their carboxylic acids 3.
Scheme 3: Chemical synthesis of the linear peptidomimetics 8.
Scheme 4: Macrocyclization strategy based on SN2’ reaction to affords the solonamide analogues 9 and their ov...
Figure 2: Effect of compounds 9e and 9g at three concentrations on the hemolysis production by S. aureus ATCC...
Figure 3: Inhibition of hemolysis (%) on human red blood cells caused by S. aureus ATCC 25923 after being in ...
Figure 4: Cell viability of human fibroblast exposed to compounds 9e (A) and 9g (B) for 24 and 48 hours. The ...
Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups
- Xiaowei Li,
- Xiaolin Shi,
- Xiangqian Li and
- Dayong Shi
Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218
- way for late-stage modifications. In the same year, Yu’s group [122] reported a Pd(II)-catalyzed C–H trifluoromethylation of arenes with an electrophilic trifluoromethylation reagent using diverse heterocyclic directing groups. Notably, the presence of trifluoroacetic acid (TFA) is crucial for the Ar
Graphical Abstract
Scheme 1: The main three strategies of fluorination: nucleophilic, electrophilic and radical fluorination.
Scheme 2: Doyle’s Pd-catalyzed fluorination of allylic chlorides.
Scheme 3: Allylic fluorination of 2- and 3-substituted propenyl esters.
Scheme 4: Regioselective allylic fluorination of cinnamyl phosphorothioate esters.
Scheme 5: Palladium-catalyzed aliphatic C–H fluorination reported by Doyle.
Scheme 6: Pd-catalyzed enantioselective fluorination of α-ketoesters followed by stereoselective reduction to...
Scheme 7: Pd-catalyzed C(sp3)–H fluorination of oxindoles.
Scheme 8: C–H fluorination of 8-methylquinoline derivatives with F− reagents.
Scheme 9: Fluorination of α-cyano acetates reported by van Leeuwen.
Scheme 10: The catalytic enantioselective electrophilic C–H fluorination of α-chloro-β-keto phosphonates.
Scheme 11: Fluorination of unactivated C(sp3)–H bonds directed by the bidentate PIP auxiliary.
Scheme 12: Fluorination of C(sp3)–H bonds at the β-position of carboxylic acids.
Scheme 13: Enantioselective benzylic C–H fluorination with a chiral transient directing group.
Scheme 14: Microwave-heated Pd-catalyzed fluorination of aryl alcohols.
Scheme 15: Fluorination of aryl potassium trifluoroborates.
Scheme 16: C(sp2)–F bond formation using precatalyst [L·Pd]2(cod).
Scheme 17: Pd-catalyzed fluorination of (hetero)aryl triflates and bromides.
Scheme 18: The Pd-catalyzed C–H fluorination of arenes with Selectfluor/NFSI.
Scheme 19: Pd(II)-catalyzed ortho-monofluorination protocol for benzoic acids.
Scheme 20: Pd-catalyzed C(sp2)–H bond fluorination of 2-arylbenzothiazoles.
Scheme 21: Nitrate-promoted fluorination of aromatic and olefinic C(sp2)–H bonds and proposed mechanism.
Scheme 22: Fluorination of oxalyl amide-protected benzylamine derivatives.
Scheme 23: C–H fluorination of benzaldehydes with orthanilic acids as transient directing group.
Scheme 24: Pd(II)-catalyzed aryl C–H fluorination with various directing groups.
Scheme 25: Cu-catalyzed aliphatic, allylic, and benzylic fluorination.
Scheme 26: Cu-catalyzed SN2 fluorination of primary and secondary alkyl bromides.
Scheme 27: Copper-catalyzed fluorination of alkyl triflates.
Scheme 28: Cu-catalyzed fluorination of allylic bromides and chlorides.
Scheme 29: Synthetic strategy for the fluorination of active methylene compounds.
Scheme 30: Fluorination of β-ketoesters using a tartrate-derived bidentate bisoxazoline-Cu(II) complex.
Scheme 31: Highly enantioselective fluorination of β-ketoesters and N-Boc-oxindoles.
Scheme 32: Amide group-assisted site-selective fluorination of α-bromocarbonyl compounds.
Scheme 33: Cu-mediated aryl fluorination reported by Sanford [77].
Scheme 34: Mono- or difluorination reactions of benzoic acid derivatives.
Scheme 35: Cu-catalyzed fluorination of diaryliodonium salts with KF.
Scheme 36: Copper(I)-catalyzed cross-coupling of 2-pyridylaryl bromides.
Scheme 37: AgNO3-catalyzed decarboxylative fluorination of aliphatic carboxylic acids.
Scheme 38: The Mn-catalyzed aliphatic and benzylic C–H fluorination.
Scheme 39: Iron(II)-promoted C–H fluorination of benzylic substrates.
Scheme 40: Ag-catalyzed fluorodecarboxylation of carboxylic acids.
Scheme 41: Vanadium-catalyzed C(sp3)–H fluorination.
Scheme 42: AgNO3-catalyzed radical deboronofluorination of alkylboronates and boronic acids.
Scheme 43: Selective heterobenzylic C–H fluorination with Selectfluor reported by Van Humbeck.
Scheme 44: Fe(II)-catalyzed site-selective fluorination guided by an alkoxyl radical.
Scheme 45: Fluorination of allylic trichloroacetimidates reported by Nguyen et al.
Scheme 46: Iridium-catalyzed fluorination of allylic carbonates with TBAF(t-BuOH)4.
Scheme 47: Iridium-catalyzed asymmetric fluorination of allylic trichloroacetimidates.
Scheme 48: Cobalt-catalyzed α-fluorination of β-ketoesters.
Scheme 49: Nickel-catalyzed α-fluorination of various α-chloro-β-ketoesters.
Scheme 50: Ni(II)-catalyzed enantioselective fluorination of oxindoles and β-ketoesters.
Scheme 51: Scandium(III)-catalyzed asymmetric C–H fluorination of unprotected 3-substituted oxindoles.
Scheme 52: Iron-catalyzed directed C–H fluorination.
Scheme 53: Electrophilic silver-catalyzed Ar–F bond-forming reaction from arylstannanes.
Figure 1: Nucleophilic, electrophilic and radical CF3 sources.
Scheme 54: Cu(I)-catalyzed allylic trifluoromethylation of unactivated terminal olefins.
Scheme 55: Direct copper-catalyzed trifluoromethylation of allylsilanes.
Scheme 56: Cupper-catalyzed enantioselective trifluoromethylation of five and six-membered ring β-ketoesters.
Scheme 57: Cu-catalyzed highly stereoselective trifluoromethylation of secondary propargyl sulfonates.
Scheme 58: Remote C(sp3)–H trifluoromethylation of carboxamides and sulfonamides.
Scheme 59: Trifluoromethylation of allylsilanes with photoredox catalysis.
Scheme 60: Ag-catalyzed decarboxylative trifluoromethylation of aliphatic carboxylic acids in aqueous CH3CN.
Scheme 61: Decarboxylative trifluoromethylation of aliphatic carboxylic acids via combined photoredox and copp...
Scheme 62: Palladium-catalyzed Ar–CF3 bond-forming reaction.
Scheme 63: Palladium-catalyzed trifluoromethylation of arenes with diverse heterocyclic directing groups.
Scheme 64: Pd-catalyzed trifluoromethylation of indoles as reported by Liu.
Scheme 65: Pd-catalyzed trifluoromethylation of vinyl triflates and vinyl nonaflates.
Scheme 66: Pd(II)-catalyzed ortho-trifluoromethylation of aromatic C–H bonds.
Scheme 67: Visible-light-induced Pd(OAc)2-catalyzed ortho-trifluoromethylation of acetanilides with CF3SO2Na.
Scheme 68: CuI-catalyzed trifluoromethylation of aryl- and alkenylboronic acids.
Scheme 69: Cu-catalyzed trifluoromethylation of aryl- and vinylboronic acids.
Scheme 70: Copper-catalyzed trifluoromethylation of α,β-unsaturated carboxylic acids.
Scheme 71: Formation of C(sp2)–CF3 bond catalyzed by copper(I) complex.
Scheme 72: Loh’s Cu(I)-catalyzed trifluoromethylation of enamides and electron-deficient alkenes.
Scheme 73: Copper and iron-catalyzed decarboxylative tri- and difluoromethylation.
Scheme 74: Cu-catalyzed trifluoromethylation of hydrazones developed by Bouyssi.
Scheme 75: Cu(I)-catalyzed trifluoromethylation of terminal alkenes.
Scheme 76: Cu/Ag-catalyzed decarboxylative trifluoromethylation of cinnamic acids.
Scheme 77: Copper-catalyzed direct alkenyl C–H trifluoromethylation.
Scheme 78: Copper(I/II)-catalyzed direct trifluoromethylation of styrene derivatives.
Scheme 79: Regioselective trifluoromethylation of pivalamido arenes and heteroarenes.
Scheme 80: Synthesis of trifluoromethylquinones in the presence of copper(I).
Scheme 81: Oxidative trifluoromethylation of imidazoheterocycles in ionic liquid/water.
Scheme 82: A mild and fast continuous-flow trifluoromethylation of coumarins using a CuI/CF3SO2Na/TBHP system.
Scheme 83: Copper-catalyzed oxidative trifluoromethylation of various 8-aminoquinolines.
Scheme 84: PA-directed copper-catalyzed trifluoromethylation of anilines.
Scheme 85: Trifluoromethylation of potassium vinyltrifluoroborates catalyzed by Fe(II).
Scheme 86: Alkenyl trifluoromethylation catalyzed by Ru(phen)3Cl2 as photocatalyst.
Scheme 87: Ru-catalyzed trifluoromethylation of alkenes by Akita’s group.
Scheme 88: Ir-catalyzed Cvinyl–CF3 bond formation of α,β-unsaturated carboxylic acids.
Scheme 89: Ag(I)-catalyzed denitrative trifluoromethylation of β-nitrostyrenes.
Scheme 90: Photocatalyzed direct trifluoromethylation of aryl and heteroaryl C–H bonds.
Scheme 91: Rhenium (MTO)-catalyzed direct trifluoromethylation of aromatic substrates.
Scheme 92: Trifluoromethylation of unprotected anilines under [Ir(ppy)3] catalyst.
Scheme 93: Oxidative trifluoromethylation of imidazopyridines and imidazoheterocycles.
Scheme 94: Ruthenium-catalyzed trifluoromethylation of (hetero)arenes with trifluoroacetic anhydride.
Scheme 95: Phosphovanadomolybdic acid-catalyzed direct C–H trifluoromethylation.
Scheme 96: Picolinamide-assisted ortho-trifluoromethylation of arylamines.
Scheme 97: A nickel-catalyzed C–H trifluoromethylation of free anilines.
Scheme 98: Cu-mediated trifluoromethylation of terminal alkynes reported by Qing.
Scheme 99: Huang’s C(sp)–H trifluoromethylation using Togni’s reagent.
Scheme 100: Cu-catalyzed methods for trifluoromethylation with Umemoto’s reagent.
Scheme 101: The synthesis of alkynyl-CF3 compounds in the presence of fac-[Ir(ppy)3] under visible-light irradi...
Scheme 102: Pd-catalyzed Heck reaction reported by Reutrakul.
Scheme 103: Difluoromethylation of enamides and ene-carbamates.
Scheme 104: Difluoromethylation of α,β-unsaturated carboxylic acids.
Scheme 105: Copper-catalyzed direct C(sp2)–H difluoroacetylation reported by Pannecoucke and co-workers.
Scheme 106: Difluoroalkylation of aldehyde-derived hydrazones with functionalized difluoromethyl bromides.
Scheme 107: Photoredox-catalyzed C–H difluoroalkylation of aldehyde-derived hydrazones.
Scheme 108: Synergistic ruthenium(II)-catalyzed C–H difluoromethylation reported by Ackermann.
Scheme 109: Visible-light photocatalytic decarboxylation of α,β-unsaturated carboxylic acids.
Scheme 110: Synthesis of difluorinated ketones via S-alkyl dithiocarbamates obtained from acyl chlorides and po...
Scheme 111: Synthesis of aryl and heteroaryl difluoromethylated phosphonates.
Scheme 112: Difluoroalkylation of secondary propargyl sulfonates using Cu as the catalyst.
Scheme 113: Ru(II)-mediated para-selective difluoromethylation of anilides and their derivatives.
Scheme 114: Bulky diamine ligand promoted cross-coupling of difluoroalkyl bromides.
Scheme 115: Copper-catalyzed C3–H difluoroacetylation of quinoxalinones.
Scheme 116: Copper(I) chloride-catalyzed trifluoromethylthiolation of enamines, indoles and β-ketoesters.
Scheme 117: Copper-boxmi-catalyzed asymmetric trifluoromethylthiolation of β-ketoesters.
Scheme 118: Direct Cu-catalyzed trifluoromethylthiolation of boronic acids and alkynes.
Scheme 119: Cu-catalyzed synthesis of α-trifluoromethylthio-substituted ketones.
Scheme 120: Trifluoromethylthiolation reactions promoted by diazotriflone and copper.
Scheme 121: Halide activation of N-(trifluoromethylthio)phthalimide.
Scheme 122: The visible light-promoted trifluoromethylthiolation reported by Glorius.
Scheme 123: Synthesis of α-trifluoromethylthioesters via Goossen’s approach.
Scheme 124: Photoinduced trifluoromethylthiolation of diazonium salts.
Scheme 125: Ag-mediated trifluoromethoxylation of aryl stannanes and arylboronic acids.
Scheme 126: Catalytic (hetero)aryl C–H trifluoromethoxylation under visible light.
Scheme 127: Photoinduced C–H-bond trifluromethoxylation of (hetero)arenes.
