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Search for "cationic" in Full Text gives 470 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

NMR Spectroscopy of supramolecular chemistry on protein surfaces

  • Peter Bayer,
  • Anja Matena and
  • Christine Beuck

Beilstein J. Org. Chem. 2020, 16, 2505–2522, doi:10.3762/bjoc.16.203

Graphical Abstract
  • protein assembling properties of calixarene ligands can further be fine-tuned by introducing additional substituents [27][28]. Gordo et al. [40] designed a cationic guanidiniomethyl-calix[4]arene with two hydrophobic loops at the narrow rim to stabilize the tetramer interface of the p53 tetramerization
  • perturbation and line broadening observed in the 1H,15N-HSQC titrations. The smallest ligand 4PSA showed the highest specificity, locating to the hydrophobic triad, where ubiquitin binds many of its protein interaction partners, which is surrounded by cationic residues. The flat, hydrophobic pyrene core can
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Published 09 Oct 2020

Recent developments in enantioselective photocatalysis

  • Callum Prentice,
  • James Morrisson,
  • Andrew D. Smith and
  • Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

Graphical Abstract
  • ]-radical shift generates α-amino radicals 248•. Simultaneously, 249 is reduced by the reduced photocatalyst to give radical anion 249•− that can then undergo a cation exchange with chiral cationic acid 250 and form a chiral ion pair 251. The two radical species then couple enantioselectively within the
  • intramolecular fashion, using alkenes 262, and an intermolecular fashion, using alkene 263 and cyclopentadiene 264 (Scheme 42) [104]. Using a similar strategy to Luo et al., Nicewicz et al. uses a preformed chiral photocatalyst composed of a cationic triaryl pyrillium, TP, twinned with a chiral counterion 265
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Published 29 Sep 2020

Efficient [(NHC)Au(NTf2)]-catalyzed hydrohydrazidation of terminal and internal alkynes

  • Maximillian Heidrich and
  • Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

Graphical Abstract
  • ; Introduction Cationic gold complexes with weakly coordinating counterions (which are often considered to be solvent-separated ions) [1][2][3], render powerful catalysts for the transformation of organic substrates [4][5][6], specifically the reactions of alkynes with a variety of heteroatom nucleophiles
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Published 26 Aug 2020

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

  • Thomas Schneider,
  • Michael Keim,
  • Bianca Seitz and
  • Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

Graphical Abstract
  • cyclobutene and several cationic intermediates and mainly yield 2-(1-phenylvinyl)indenes. In a similar reaction cascade, a fulvene derivative was obtained with 1,4-diphenylbutadiene as the substrate. Keywords: alkynes; aromatic substitution; cyclization; cycloaddition; iminium salts; Introduction In recent
  • -substituted iminium groups with electron-rich (hetero)aromatics are known [18][24]. Furthermore, 1-(trifluoromethyl)indenes have recently been generated by cationic cyclization of β-aryl trifluoromethyl enones under superacid conditions [42][43][44]. Styrenes are also known to behave as dienes in [4 + 2
  • analogous to 21 could be isolated [56]. A cationic 1,5-cylization converts 21 into cyclopentene 22, from which fulvene 19 is formed by deprotonation and a formal 1,4-shift of the NMe2 group. The details of this rearrangement are not known, an N,N-dimethyldihydropyrrolium intermediate may be involved
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Published 24 Aug 2020

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

  • Annike Weißenstein,
  • Myroslav O. Vysotsky,
  • Ivo Piantanida and
  • Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

Graphical Abstract
  • molecules. In addition to the pH value, the hydrolysis also depends on the position of cationic ammonium groups, namely, the distance of the charged group from the imide position is proportional to its stability [24]. However, too long side chains can interfere with threading intercalation into ds-DNA/RNA
  • preparative HPLC and treatment with 1 M HCl solution, NDI 5 with three cationic substituents at the imide and bay positions could be obtained in 44% yield. The 1H, 13C NMR data, and high-resolution mass spectra correspond well with the structures of all new compounds synthesised. Spectrophotometric properties
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Published 19 Aug 2020

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

  • Goutam Ghosh and
  • Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

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  • , as mentioned above. The pH-responsive self-assembling behavior of peptides has a great importance in drug delivery, and since PEP-1 contains rich cationic residues, such as Arg, this system can be an interesting potential candidate for DDS and as an antibacterial agent [71]. Biocompatibility, drug
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Published 17 Aug 2020

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

  • Rémi Martinent,
  • Javier López-Andarias,
  • Dimitri Moreau,
  • Yangyang Cheng,
  • Naomi Sakai and
  • Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

Graphical Abstract
  • offsetting a charge repulsion of the extra lysine residues, and thus allowing the formation of stable cationic nanofibers. These nanoaggregates, assembled from the monomer 16, are efficient gene transfection vectors. However, the control peptide 17, which cannot self-assemble into nanotubes, shows negative
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Published 14 Aug 2020

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

  • Olusesan K. Koleoso,
  • Matthew Turner,
  • Felix Plasser and
  • Marc C. Kimber

Beilstein J. Org. Chem. 2020, 16, 1983–1990, doi:10.3762/bjoc.16.165

Graphical Abstract
  • conjugated N-acyliminium 14. The iminium 14 could then undergo traditional nucleophilic addition giving the addition product. Given that the iridium complex Ir[(ppy)2(dtbbpy)]PF6 had been effective [47][48][50] in this radical/cationic pathway with enamides we would now like to report our preliminary
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Published 12 Aug 2020

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

  • Lucas Guillemard and
  • Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

Graphical Abstract
  • ). Thereafter, a cationic intermediate is afforded by the radical combination between the sulfonyl radical and the 1-naphthyl derivative at the C4 position. Lastly, a proton-transfer process and dissociation result in the formation of the expected coupling product, accompanied by the regeneration of the Cu salt
  • ) catalyst, followed by SET oxidation to provide an Ar–Au(III) intermediate (Figure 43). This Lewis-acidic Au species promotes the regioselective C–H auration of the electron-rich substrate, delivering a cationic intermediate that under deprotonation and subsequent reductive elimination furnishes the
  • transfer generate the aryl radical together with a cationic Mn species. The addition of the aryl radical to the (hetero)aromatic substrate affords a radical biaryl intermediate that provides the expected coupling product after oxidation and deprotonation. C–H activation of heterocyclic substrates The panel
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Published 21 Jul 2020

Fluorohydration of alkynes via I(I)/I(III) catalysis

  • Jessica Neufeld,
  • Constantin G. Daniliuc and
  • Ryan Gilmour

Beilstein J. Org. Chem. 2020, 16, 1627–1635, doi:10.3762/bjoc.16.135

Graphical Abstract
  • fluorinating reagents [44][45]. Developments by Hammond and Xu validated N-pyridine oxides as terminal oxidants to substitute Selectfluor® for the cationic Au(I)/Au(III) cycle, thereby enabling high functional group tolerance [46][47][48][49]. Inspired by these and other selected advances [50][51], in metal
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Published 10 Jul 2020

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
  • immobilisation is common with transition metal complexes as they are often inherently cationic species. Amara and co-workers recently showed that [Ru(bpy)3]2+ could be immobilised on silica particles with a dramatic increase in the efficiency of the photooxidation of terpenes [137]. Polymer networks containing
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Published 26 Jun 2020

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

  • Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

Graphical Abstract
  • -substituted cation 19 favors the radical cyclization path because the stabilization by an α-substituent makes its cation center more stable and less reactive. In contrast, the non-α-substituted cation 19 prefers the cationic cyclization. However, the two cyclization processes form the intermediates 20 and 21
  • regenerates for the next catalytic cycle. The other plausible reaction pathway 2 starts with a SET from the excited Hantzsch ester 44 to the acetamide 46 to form the intermediate difluoroamide radical 48 and the cationic radical 51. The subsequent addition of alkenes to the formed radical 48 and HAT from the
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Published 23 Jun 2020

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

  • Carlos H. Escalante,
  • Eder I. Martínez-Mora,
  • Carlos Espinoza-Hicks,
  • Alejandro A. Camacho-Dávila,
  • Fernando R. Ramos-Morales,
  • Francisco Delgado and
  • Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

Graphical Abstract
  • electronic density provided by the nitrogen lone-pair, which plausibly stabilizes the cationic or radical species formed by the oxidant reagent during the aromatization process [46], as efficiently occurred with derivatives 9. Finally, in order to obtain the aromatic indole-based pentacycles 12, the
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Published 17 Jun 2020

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

  • Stephanie G. E. Amos,
  • Marion Garreau,
  • Luca Buzzetti and
  • Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

Graphical Abstract
  • alkyl group (Me in OD2) to an aryl group (Ph in OD3), they could limit the photocatalyst bleaching due to the demethylation of the organic dye. Alkene radical anions have been less exploited than their cationic equivalents. In 2017, the Lei group developed a Markovnikov-selective hydrosulfonylation
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Published 29 May 2020

Development of fluorinated benzils and bisbenzils as room-temperature phosphorescent molecules

  • Shigeyuki Yamada,
  • Takuya Higashida,
  • Yizhou Wang,
  • Masato Morita,
  • Takuya Hosokai,
  • Kaveendra Maduwantha,
  • Kaveenga Rasika Koswattage and
  • Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 1154–1162, doi:10.3762/bjoc.16.102

Graphical Abstract
  • oxygen atom in DMSO to construct a cationic vinylpalladium(II) species (Int-B). Further nucleophilic attack of another DMSO molecule against Int-B, followed by elimination of dimethyl sulfide, furnishes a cationic intermediate (Int-C). Finally, immediate elimination of dimethyl sulfide and the Pd(II
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Published 29 May 2020

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

  • Phil M. Pithan,
  • Sören Steup and
  • Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

Graphical Abstract
  • –oxidation reaction under aerobic conditions [51][52][53]. In this context, we were interested in the effect of a positively charged arylvinyl substituent on the photochromic properties of the spironaphthoxazine. For this purpose, we chose the quinolizinium ion as the cationic aryl substituent because it has
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Published 05 May 2020

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

Graphical Abstract
  • (cationic) molecules [TS(1→14)]. However, this arrangement is not stable, and a stabilized homodimer with a pentavalent P atom 14 is formed immediately. This quasi-autocatalytic process decreases significantly the enthalpy demand of the TS to a reliable level, and finally it gives the corresponding 2
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Published 22 Apr 2020

Copper-catalyzed remote C–H arylation of polycyclic aromatic hydrocarbons (PAHs)

  • Anping Luo,
  • Min Zhang,
  • Zhangyi Fu,
  • Jingbo Lan,
  • Di Wu and
  • Jingsong You

Beilstein J. Org. Chem. 2020, 16, 530–536, doi:10.3762/bjoc.16.49

Graphical Abstract
  • Pd(II) species to more electrophilic high-valent cationic Pd(IV). In addition, this protocol is not compatible with other PAHs except naphthalene, such as phenanthrene, pyrene and fluoranthene, and cannot tolerate some special functional groups, such as alkenyl and alkynyl groups. As a component part
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Published 30 Mar 2020

Exploring the scope of DBU-promoted amidations of 7-methoxycarbonylpterin

  • Anna R. Bockman and
  • Jeffrey M. Pruet

Beilstein J. Org. Chem. 2020, 16, 509–514, doi:10.3762/bjoc.16.46

Graphical Abstract
  • ion pairs with the cationic DBU-activated acyl intermediate (see Figure 1). However, the α-substitution in alanine clearly abolishes any rate acceleration driven by ionic interactions, and most α-substituted amines had similar rates. Rate acceleration is recovered in serine, owing to the effect of the
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Published 26 Mar 2020

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

  • Faïma Lazreg,
  • Marie Vasseur,
  • Alexandra M. Z. Slawin and
  • Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

Graphical Abstract
  • catalytic strategy for the one-pot synthesis of N-sulfonylamidines is described. The cationic copper(I) complexes were found to be highly active and efficient under mild conditions in air and in the absence of solvent. A copper acetylide is proposed as key intermediate in this transformation. Keywords
  • ]. Based on these earlier results, the reactivity of these catalysts was investigated in the context of achieving formation of the challenging sulfonamide derivatives. Herein, we report the high efficiency of cationic copper(I) complexes for the formation of N-sulfonylamidines via a three-component
  • deprotonates the triazolium salt (Scheme 2). The reactivity of a series of cationic copper(I) complexes (1–6) was evaluated at 0.5 mol % loading using tosyl azide, phenylacetylene and diisopropylamine as benchmark substrates [31][32]. Various solvents were evaluated at room temperature under aerobic conditions
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Published 24 Mar 2020

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

  • Bernd Strehmel,
  • Christian Schmitz,
  • Ceren Kütahya,
  • Yulian Pang,
  • Anke Drewitz and
  • Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

Graphical Abstract
  • in this field and helped to understand the function of existing intrinsic barrier in such systems comprising cationic cyanines in photoinduced electron transfer systems [65]. Furthermore, the huge amount of heat released by nonradiative deactivation of the excited state brings up to use them as
  • of either I, II, III, IV or V with distinct terminal groups A/A’ results in cyanines exhibiting either a cationic, zwitterionic or anionic pattern. Their solubility covers a wide range including aprotic polar organic solvents or also water. The latter requests to introduce functional groups promoting
  • anions promoting the solubility in organic surroundings. Representative anions in the case of cationic absorbers relate to tosylate [5], [n-C12H25-Ph-SO3−] [5], FAP ([(C2F5)3PF3]−)[71], NTf2 ([(CF3SO2)2N]−) [5] or aluminates ([Al(t-C4F9O)4]−) [6] – just to count a few possible examples. Thus, replacement
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Published 18 Mar 2020

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

  • Sarah Kölsch,
  • Heiko Ihmels,
  • Jochen Mattay,
  • Norbert Sewald and
  • Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

Graphical Abstract
  • particular cationic ones, were shown to be efficient DNA binders [47][48][49][50][51][52][53][54][55][56][57][58]. Nevertheless, the photochromic nature of DNA-binding styryl dyes has not been applied to use them as photoswitchable DNA binders. Although, there is one reported example that demonstrates the
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Published 23 Jan 2020

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

  • Katarzyna Włodarczyk,
  • Piotr Borowski and
  • Marek Stankevič

Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11

Graphical Abstract
  • our previous papers [56][57], we described the intramolecular cationic cyclization of β-hydroxyalkylphosphine oxides (Scheme 2). Depending on the structure, the formation of either the phosphaindane 3 or the benzophosphorinane 2 skeleton was observed. This method could also be performed in a
  • stereoselective manner, given that corresponding chiral substrates were used for the cyclization. The chiral compounds suitable for cyclization could be obtained by desymmetrization of phosphine sulfides (Scheme 3) [58]. In order to gain insight into the cationic cyclization of β-hydroxyalkylphosphine sulfides, a
  • cationic intermediates underwent hydrolysis during aqueous workup, leading to the observed products. It was assumed that a similar sulfur atom migration should occur in the presence of Brønsted acid under dry conditions. Therefore, a set of phosphine sulfides prepared above was subjected to the reaction
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Published 21 Jan 2020

Light-controllable dithienylethene-modified cyclic peptides: photoswitching the in vivo toxicity in zebrafish embryos

  • Sergii Afonin,
  • Oleg Babii,
  • Aline Reuter,
  • Volker Middel,
  • Masanari Takamiya,
  • Uwe Strähle,
  • Igor V. Komarov and
  • Anne S. Ulrich

Beilstein J. Org. Chem. 2020, 16, 39–49, doi:10.3762/bjoc.16.6

Graphical Abstract
  • the ring-closed and ring-opened isomers, we can presume that homodimerization may affect the way in which the peptides interact with their molecular targets, or it may compromise their long-term biostability. Likewise, an elongation of the β-sheet core and an increase in cationic charge density
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Published 07 Jan 2020

Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

  • Renata Kaczmarek,
  • Dariusz Korczyński,
  • James R. Green and
  • Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

Graphical Abstract
  • material containing the propargyl alcohol derivative unit. The chemistry of cationic propargyl dicobalt complexes, recognized as the Nicholas reaction, has become one of the most widely appreciated forms of metalorganic chemistry. These cations are generated most commonly from propargyl alcohol, -ether, or
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Published 02 Jan 2020
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