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Search for "quenching" in Full Text gives 395 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

  • Prodip Howlader and
  • Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

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  • -bonding, which would lead to catalytic quenching, a unique design strategy was applied. Instead of using a cis-blocked palladium(II) unit for self-assembly, Pd(NO3)2 was employed along with the triazole-based 0° clip 13. In a one-pot reaction, 12 and 13 in DMSO were treated with Pd(NO3)2 in a 1:1:1 ratio
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Published 27 May 2022

Syntheses of novel pyridine-based low-molecular-weight luminogens possessing aggregation-induced emission enhancement (AIEE) properties

  • Masayori Hagimori,
  • Tatsusada Yoshida,
  • Yasuhisa Nishimura,
  • Yukiko Ogawa and
  • Keitaro Tanaka

Beilstein J. Org. Chem. 2022, 18, 580–587, doi:10.3762/bjoc.18.60

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  • quenched due to aggregation-caused quenching (ACQ) [10]. Generally, the restriction of intermolecular π–π interactions in highly planar compounds plays a key role in aggregate structures exhibiting fluorescence [5][6][10]. In addition, intramolecular mechanisms, such as intramolecular rotation (RIR
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Published 24 May 2022

Tetraphenylethylene-embedded pillar[5]arene-based orthogonal self-assembly for efficient photocatalysis in water

  • Zhihang Bai,
  • Krishnasamy Velmurugan,
  • Xueqi Tian,
  • Minzan Zuo,
  • Kaiya Wang and
  • Xiao-Yu Hu

Beilstein J. Org. Chem. 2022, 18, 429–437, doi:10.3762/bjoc.18.45

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  • light irradiation. In addition, the AIE donor molecules allowed an ordered arrangement of the loaded negatively charged dye acceptor on the positively charged surface, which might avoid aggregation-caused quenching effects and produced better catalytic efficiency. These results revealed that the m
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Published 13 Apr 2022

Flow synthesis of oxadiazoles coupled with sequential in-line extraction and chromatography

  • Kian Donnelly and
  • Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 232–239, doi:10.3762/bjoc.18.27

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  • an integrated quenching and extraction step. Lastly, the use of an automated in-line chromatography system was exploited to realise a powerful flow platform for the generation of the heterocyclic targets. Keywords: chromatography; flow synthesis; in-line purification; oxadiazole; reaction
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Published 25 Feb 2022

Efficient N-arylation of 4-chloroquinazolines en route to novel 4-anilinoquinazolines as potential anticancer agents

  • Rodolfo H. V. Nishimura,
  • Thiago dos Santos,
  • Valter E. Murie,
  • Luciana C. Furtado,
  • Leticia V. Costa-Lotufo and
  • Giuliano C. Clososki

Beilstein J. Org. Chem. 2021, 17, 2968–2975, doi:10.3762/bjoc.17.206

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  • of the anticancer agent verubulin. Thus, after regioselective 4-chloroquinazoline metalation by an in situ trapping metalation strategy, reaction quenching with iodine allowed us to isolate 4-chloro-8-iodoquinazoline in 83% yield. Surprisingly, further reaction of 4-chloro-8-iodoquinazoline with 4
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Published 22 Dec 2021

DABCO-promoted photocatalytic C–H functionalization of aldehydes

  • Bruno Maia da Silva Santos,
  • Mariana dos Santos Dupim,
  • Cauê Paula de Souza,
  • Thiago Messias Cardozo and
  • Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

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  • radical hydrogen abstraction may be possible under similar conditions [31][32]. However, even small amounts of DABCO (Table 1, entry 1) seem to completely shut down this alternative path, probably due to a fast quenching of the excited state photocatalyst, leading to no mechanism competition under the
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Published 21 Dec 2021

Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode

  • Ettore Crovini,
  • Zhen Zhang,
  • Yu Kusakabe,
  • Yongxia Ren,
  • Yoshimasa Wada,
  • Bilal A. Naqvi,
  • Prakhar Sahay,
  • Tomas Matulaitis,
  • Stefan Diesing,
  • Ifor D. W. Samuel,
  • Wolfgang Brütting,
  • Katsuaki Suzuki,
  • Hironori Kaji,
  • Stefan Bräse and
  • Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 2894–2905, doi:10.3762/bjoc.17.197

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  • (Supporting Information File 1, Figure S5a) with a corresponding ΦPL of 29% under N2. The significantly red-shifted emission in the PMMA film compared to that in toluene coupled with a significantly lower ΦPL is suggestive that aggregation-caused quenching is prevalent in this host matrix. Transient PL
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Published 08 Dec 2021

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

  • Qingkai Zeng,
  • Qiumeng Long,
  • Jihong Lu,
  • Li Wang,
  • Yuting You,
  • Xiaoting Yuan,
  • Qianjun Zhang,
  • Qingmei Ge,
  • Hang Cong and
  • Mao Liu

Beilstein J. Org. Chem. 2021, 17, 2840–2847, doi:10.3762/bjoc.17.195

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  • +, and Mn2+ (nitrate salts were used as cation sources) in DMF resulted in different degrees of quenching of the fluorescence emission of host 4. The results are collected in Figure 3 as the corresponding fluorescence quenching efficiency which was quantified using the equation ΔI = (I0 − I), where I is
  • the fluorescence intensity response of the aminobenzene-containing hemicucurbituril 4 in the presence of metal cations, and I0 represents the corresponding fluorescence intensity in the absence of such metal cations. The addition of Fe3+ and Cu2+ caused a significant quenching of the fluorescence
  • halide ions, especially the heavier iodide ion, to the macrocyclic sensor, slightly enhanced the fluorescence emission in CH2Cl2/CH3OH 4:1 (v/v) at 298 K, instead of quenching the fluorescence as predicted by the classic heavy-atom effect. The corresponding fluorescence enhancement efficiency of selected
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Published 06 Dec 2021

Visible-light-mediated copper photocatalysis for organic syntheses

  • Yajing Zhang,
  • Qian Wang,
  • Zongsheng Yan,
  • Donglai Ma and
  • Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

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  • oxidized RuIII, which subsequently accepts an electron from an external donor (D) to form the ground-state catalyst RuII. This type of reaction mechanism is an oxidative quenching cycle (OQC). Alternatively, the lower energy SOMO of the excited state RuII* can accept an electron from an external donor
  • , which is referred to as a reductive quenching cycle (RQC; Scheme 1). Compared with the photoredox mechanism of ruthenium-based catalysts, copper complexes show unique features [22][28]. Under irradiation, the copper complex CuI is converted to the excited state CuI*, which transfers electrons to an
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Published 12 Oct 2021

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

  • Songeziwe Ntsimango,
  • Kennedy J. Ngwira,
  • Moira L. Bode and
  • Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

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  • . Once intermediate 18b is formed an H+ is abstracted by an acetate ion from the methoxy substituent again forming formaldehyde and acetic acid, along with subsequent quenching of the cation to restore aromaticity. Examples of photoredox-catalyzed cation radical accelerated reactions with the aromatic
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Published 08 Sep 2021

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

  • Pieterjan Winant and
  • Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

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  • through oxidative quenching of the excited substrate. While an excited state of 1 could react in a similar fashion, the absorption maximum of 1 is centered around 280 nm, which is outside the emission spectrum of green LEDs. A recent study by Hashmi et al. [44], however, shed a completely different light
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Published 06 Sep 2021

Photoredox catalysis in nickel-catalyzed C–H functionalization

  • Lusina Mantry,
  • Rajaram Maayuri,
  • Vikash Kumar and
  • Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

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  • developments, which enables a diverse range of previously inaccessible organic transformations in milder reaction conditions [31][32][33][34][35][36][37][38][39][40]. Here, by absorbing visible light, a photocatalyst can function as a single-electron redox mediator through an oxidative or reductive quenching
  • functionalizations are scarce and present new opportunities for further exploration. In consideration of the sustainable nature of C–H activation by photoredox nickel catalysis, further exciting developments are expected in this rapidly evolving research area. Oxidative and reductive quenching cycles of a
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Published 31 Aug 2021

Constrained thermoresponsive polymers – new insights into fundamentals and applications

  • Patricia Flemming,
  • Alexander S. Münch,
  • Andreas Fery and
  • Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

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Published 20 Aug 2021

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

  • Renato L. Carvalho,
  • Amanda S. de Miranda,
  • Mateus P. Nunes,
  • Roberto S. Gomes,
  • Guilherme A. M. Jardim and
  • Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

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  • target lactone in 61% yield over two steps. The final steps involved a one-pot ozonolysis with quenching under Pinnick oxidation conditions to afford the carboxylic acid derivative in 83% yield, followed by White’s selective C–H oxidation (Scheme 26B). White’s selective C–H oxidation was also applied in
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Published 30 Jul 2021

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

  • Nikita Brodyagin,
  • Martins Katkevics,
  • Venubabu Kotikam,
  • Christopher A. Ryan and
  • Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

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  • ]. Melting of a duplex formed by 2-aminopurine-modified PNA and complementary DNA increased the fluorescence signal, which had likely been quenched by adjacent nucleobases in the duplex [142]. Interestingly, quenching was also observed in a single stranded PNA alone, which diminished the applicability of 2
  • ]. Inspired by these findings, Cheruiyot and Rozners attempted to design fluorescent analogues of 2-aminopyridine; PhEthM (Figure 10) gave the best binding and fluorescence properties, but was strongly quenched upon formation of PNA–dsRNA triplex [147]. In general, quenching of PNA fluorescence upon binding
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Published 19 Jul 2021

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

  • Premansh Dudhe,
  • Mena Asha Krishnan,
  • Kratika Yadav,
  • Diptendu Roy,
  • Krishnan Venkatasubbaiah,
  • Biswarup Pathak and
  • Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

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  • moderately polar dichloromethane and then highly polar DMSO (Table 2, Figure 3). The fluorescence quenching of 3ac in methanol is attributed to the partial protonation of the carboline unit's nitrogen atoms facilitated by polar-protic solvents [33]. The fluorescence lifetimes were measured by time-correlated
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Published 17 Jun 2021

Double-headed nucleosides: Synthesis and applications

  • Vineet Verma,
  • Jyotirmoy Maity,
  • Vipin K. Maikhuri,
  • Ritika Sharma,
  • Himal K. Ganguly and
  • Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

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Published 08 Jun 2021

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

  • Guido Gambacorta,
  • James S. Sharley and
  • Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

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  • close to optimal as possible. Certain drawbacks to using a flow-approach must also however be acknowledged. Problems may arise due to quenching requirements, the necessity for solvent switching, concentration limitations, compensating for different encountered reaction kinetics over multiple steps when
  • mixing elements, reactor residence coils, heating/cooling segments and additional downstream components such as phase separators, quenching stages and crystallisers. A typical flow reactor will comprise two or more pumps (isocratic/peristaltic/syringe) that feed an HPLC manifold (into which samples may
  • reagents has also greatly aided in the development of impressive sequential multistep sequences in flow by acting as direct in-line quenching, work-up and purification steps [28][80][81][82][83][84][85]. Indeed, the scavenger approach to removing excess solution phase reagents or byproducts has had a
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Published 18 May 2021

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

  • Joseane A. Mendes,
  • Paulo R. R. Costa,
  • Miguel Yus,
  • Francisco Foubelo and
  • Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

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Published 12 May 2021

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

  • Mikhail K. Klychnikov,
  • Radek Pohl,
  • Ivana Císařová and
  • Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

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  • enolate formation from 8h,i with s-BuLi, a deuterium quenching experiment with D2O was performed. Analysis by 1H NMR spectroscopy revealed 87 and 91% deuterium incorporation, respectively, indicating that a deprotonation occurred, but the epoxide opening was hampered by the combination of a sterically
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Published 09 Mar 2021

A sustainable strategy for the straightforward preparation of 2H-azirines and highly functionalized NH-aziridines from vinyl azides using a single solvent flow-batch approach

  • Michael Andresini,
  • Leonardo Degannaro and
  • Renzo Luisi

Beilstein J. Org. Chem. 2021, 17, 203–209, doi:10.3762/bjoc.17.20

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  • the microfluidic system was collected in a round bottom flask cooled at −78 °C, and reacted with 1.2 equivalents of phenyllithium (PhLi) [34][35]. The mixture was stirred at the same temperature for 5 minutes, before quenching with water. To our delight, product 3a was isolated in 49% yield. Next, the
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Published 20 Jan 2021

Progress in the total synthesis of inthomycins

  • Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

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  • derivative (rac)-63 was subjected to undergo acetylation, acid chloride formation, and quenching with ammonium hydroxide to produce amide derivative (rac)-64 in 70% yield. Finally, saponification of acetate (rac)-64 using lithium hydroxide gave racemic inthomycin A ((rac)-1) in 14% overall yield (Scheme 5
  • vinylogous Mukaiyama aldol reaction to produce the desired aldehyde (rac)-118 in 81% yield. Meanwhile, the TIPS protection of oxazole 119 and then subsequent lithiation at the C-5 position and quenching in situ with allyl bromide furnished oxazole derivative 121 in 90% yield (Scheme 16). An attempted cross
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Published 07 Jan 2021

Circularly polarized luminescent systems fabricated by Tröger's base derivatives through two different strategies

  • Cheng Qian,
  • Yuan Chen,
  • Qian Zhao,
  • Ming Cheng,
  • Chen Lin,
  • Juli Jiang and
  • Leyong Wang

Beilstein J. Org. Chem. 2021, 17, 52–57, doi:10.3762/bjoc.17.6

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  • considering the side chain. At the same time, the loose stacking of the TB unit and its derivatives, which is caused by its V-configuration could reduce the distance-dependent intermolecular quenching effect in the aggregation state [16]. Moreover, the large dihedral angle of TB (80–104°) [15] permits less
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Published 06 Jan 2021

The fluorescence of a mercury probe based on osthol

  • Guangyan Luo,
  • Zhishu Zeng,
  • Lin Zhang,
  • Zhu Tao and
  • Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 22–27, doi:10.3762/bjoc.17.3

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  • , and high sensitivity [10][11][12]. In recent years, many fluorescent molecular probes have been reported. Because Hg2+ has a very strong quenching effect on fluorescence, most of the fluorescent molecular Hg2+ probes are of the fluorescence-quenching type and are easily interfered with by other
  • quenching processes [13][14][15][16][17]. Fluorescence-enhanced probes have received wide attention because of their enhanced fluorescence signal, which can better exclude the influence of instrument noise and other factors, reduce measurement errors, and thus have a higher sensitivity. Osthol (OST) is a
  • +, a coexisting ion experiment was carried out (Figure 2) [24]. The fluorescence intensity was measured by adding 1.2 × 10−4 mol∙L−1 of various metal ions to the OST–Hg2+ (c = 3.0 × 10−5 mol∙L−1) probe system. It is found that Fe3+ had a certain fluorescence quenching effect on the system due to the
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Published 05 Jan 2021

Naphthalonitriles featuring efficient emission in solution and in the solid state

  • Sidharth Thulaseedharan Nair Sailaja,
  • Iván Maisuls,
  • Jutta Kösters,
  • Alexander Hepp,
  • Andreas Faust,
  • Jens Voskuhl and
  • Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

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  • substitution and environment is reported with potential applications in sensing, bioimaging and optoelectronics. Keywords: aggregation caused quenching (ACQ); aggregation-induced emission enhancement (AIEE); naphthalonitriles (NCNs); solution and solid state emitters (SSSE); solvent quenching (SQ
  • aromatic rings that emit efficiently in very dilute solutions. However, the photoluminescence quantum yields tend to decrease or even fully quench in the aggregated or solid states, due to the well-known effect of aggregation caused quenching (ACQ) [9][10]. This is mainly related to intersystem crossing
  • , we observe a drastic drop in quantum yield when the water fractions are raised from 0% to 30%. As NMe2 is a pure push–pull system, the excited state can interact strongly with the solvent and due to the high polarity of water, a solvent quenching (SQ) effect is expected and also explains the observed
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Published 02 Dec 2020
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