pH-Responsive fluorescent supramolecular nanoparticles based on tetraphenylethylene-labelled chitosan and a six-fold carboxylated tribenzotriquinacene

• Nan Yang,
• Yi-Yan Zhu,
• Wei-Xiu Lin,
• Yi-Long Lu and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2023, 19, 635–645, doi:10.3762/bjoc.19.45

• , conventional fluorescent dyes exhibit aggregation-caused quenching (ACQ) when introduced into nanoparticles at high loads, resulting in poor fluorescence imaging quality. In recent years, tetraphenylethylene (TPE)-based dyes have been frequently used to overcome the ACQ problem due to their unique aggregation

• illumination in the solid state due to powerful self-quenching effects in the aggregates [25]. Strong emission is observed at approximately 485 nm for all CS-TPE bioconjugates in the solid state (Figure 2b). A major reason for the emission behavior is the restriction in intramolecular rotation (RIR) of

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• that a higher degree of aromatic surfaces overlapping and cation–π interactions also yield excimer fluorescence quenching [30][32][33]. This conclusion is strongly in line with experimental insight reported here and helps in explaining the observed excimer fluorescence quenching with a decrease in the

• response concerning the excimer band was obtained independently on polynucleotide’s structure and/or base composition. Fluorescence quenching upon binding was similar to the previously published bispyrene–guanidiniocarbonyl compound, which was found to bind along the phosphate backbone of most of examined

• Information File 1). Compound Phen-Py-1 showed high, micromolar/submicromolar affinities for all examined polynucleotides. The binding of Phen-Py-1 to polynucleotides possibly led to the unstacking of intramolecular pyrene–phenanthridine dimer and consequent excimer fluorescence quenching independently of the

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• authors were able to achieve enantioselectivities of up to 99%. Unfortunately, only two examples of electrophilic capturing were explored, using CD3CO2D to give deuterated products and I2. Most reports simply underwent protodemetalation upon quenching to afford the monosubstituted bicyclic alkene. The

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• fluorescence investigation of hybrid 96 revealed that the fluorescence of zinc porphyrin was strongly quenched, and the electron-transfer quenching mechanism was validated by easy oxidation. Furthermore, femtosecond transient-absorption spectrum investigations offered proof of the charge-separation process

• relatively inefficient quenching of the ZnP singlet excited state, slow charge separation, and fast charge recombination processes on the visible excitation of ZnP and UV excitation of NDI chromophores. On the other hand, excitation of the NDI chromophore leads to the charge separation via both singlet and

• triplet quenching pathways. The construction of water-soluble porphyrin nanospheres was reported by Zhang et al. in 2014 [54] by intramolecular host–guest interactions using porphyrin 126 containing two permethyl-β-cyclodextrin (PM-β-CD) and two dicarboxylatophenyl arms at meso-positions. The synthesis of

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• conditions were subjected to extensive studies for optimization. The intermediate hydrindanone enal fragment 142, bearing both an aldehyde and an alkene function, was subjected to rigorously anaerobic conditions, in the presence of 3 equivalents of SmI2, 6 equivalents of H2O, and TMSCl as a quenching agent

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• delocalized enolate intermediate 6a·Li. To that end, the addition of lithiocyclopentadiene to 2 was followed by the attendant quenching with a methylating reagent (MeI, Me2SO4, MeOTf) but a complex mixture of products was consistently obtained. To gather information on the reactivity of 6a·Li, the stabilized

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• addition, the successful integration of effective inline purification tools can mitigate safety risks during work-up (i.e., quenching of left-over reactive species) and reduce cost and time associated with traditional batch mode purifications, especially at larger scale (>100 g) [34][35][36]. Different

• -step synthesis of captopril [60], or atazanavir [61]. In the last example, the authors solve a clogging issue of the membrane by using a guard column ahead of the extraction unit. A dual application of aqueous quenching in addition to solvent swap is an interesting implementation of these membranes in

• -alkylation reaction which includes quenching, phase separation, and final filtration. After a thorough study of conditions to avoid clogging, a long run processing >100 g was achieved, giving the product in 95% yield and >99% purity [116]. The same authors also reported the crystallization of a simple

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

• Keith P. Reber and
• Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

• ] and subsequently hydrolyzed to give 4), we added excess DIBAL and allowed the reaction mixture to stir at room temperature for an additional 24 hours. Upon quenching the reaction with a saturated aqueous solution of potassium sodium tartrate (Rochelle’s salt), we were astonished to observe the clean

A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• under an argon atmosphere, and then added via syringe to the substrate. The mixture was stirred at 0 °C for one hour. Subsequent quenching was achieved by the addition of saturated bicarbonate solution (10 mL) and further stirring for one hour. Afterwards, two spoons of silica were added and the whole

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• quenching in polar solvents is less significant than that of NI-PTZ (Figure 2b), and the CT emission band is blue-shifted as compared to that of NI-N-PTZ [20], a likely consequence of the reduced electron-donating ability of the PTZ moiety. For NI-PTZ2, a solvent polarity-dependent fluorescence band was

• , one should be careful with the interpretation of such data, as the quenching of the fluorescence in aerated solution does not necessarily imply TADF, since fluorescence species with long fluorescence lifetime can be also quenched by O2 (a paramagnetic species). This is in particular relevant for the

Characterization of a new fusicoccane-type diterpene synthase and an associated P450 enzyme

• Jia-Hua Huang,
• Jian-Ming Lv,
• Liang-Yan Xiao,
• Qian Xu,
• Fu-Long Lin,
• Gao-Qian Wang,
• Guo-Dong Chen,
• Sheng-Ying Qin,
• Dan Hu and
• Hao Gao

Beilstein J. Org. Chem. 2022, 18, 1396–1402, doi:10.3762/bjoc.18.144

• stereogenic centers at C2, C6, C10, and C14 introduced during the two cyclization steps, FC-type diterpene synthases (DTSs) could be divided into 16 subtypes [20]. Furthermore, considering the modes of potential carbocation rearrangement and final carbocation quenching, there might be more FC-type DTSs in

Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells

• Merve Karaman,
• Abhishek Kumar Gupta,
• Subeesh Madayanad Suresh,
• Tomas Matulaitis,
• Lorenzo Mardegan,
• Daniel Tordera,
• Henk J. Bolink,
• Sen Wu,
• Stuart Warriner,
• Ifor D. Samuel and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2022, 18, 1311–1321, doi:10.3762/bjoc.18.136

• films, the emission for both compounds are red-shifted and significantly quenched (Figure S28 in Supporting Information File 1); indeed, the ΦPL for the neat film of DiKTa-OBuIm is only 9% while we could not ascertain a reliable value for DiKTa-DPA-OBuIm. Severe aggregation-caused quenching of the

Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

• Blaine G. Fiss,
• Georgia Douglas,
• Michael Ferguson,
• Jorge Becerra,
• Jesus Valdez,
• Trong-On Do,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2022, 18, 1203–1209, doi:10.3762/bjoc.18.125

• quenching in water and ethanol at the end of the aging step. g-h-PCN300 featured the same three major carbon 1s peaks at 284.8, 286.2 and 288.2 eV for C=N/C=C, C=O and C–OH species, respectively, as well as the charging peak seen in g-h-PCN. In g-h-PCN300, a reduction of the C=N ratio to 37%, reduction of C

Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation

• Ashish Kumar Mazumdar,
• Gyana Prakash Nanda,
• Nisha Yadav,
• Upasana Deori,
• Upasha Acharyya,
• Bahadur Sk and
• Pachaiyappan Rajamalli

Beilstein J. Org. Chem. 2022, 18, 1177–1187, doi:10.3762/bjoc.18.122

• base fumes, etc. [10][11]. However, the fluorescence quantum yield of such emitters in the solid state is relatively low due to the aggregation-caused quenching (ACQ) effect [12][13][14] and limits practical applications. Hence, metal-free emitters with high photoluminescence quantum yield (PLQY) in

• metal-based emitters in organic light-emitting diode (OLED) devices [18]. Nevertheless, many TADF emitters suffer from quenching of the emission due to the aggregation-caused quenching effect [19][20]. The strong π–π-stacking interactions in the solid or aggregated state may lead to emission quenching

• twisted intramolecular CT state led to fluorescence quenching in the highly polar water/THF mixture (10–70 vol % water, Figure 3a, c, and e) [34][35][36]. It again started glowing when the water fraction was increased beyond 80 vol % (Figure 3a, c, and e). The formation of molecular aggregates in >80 vol

On Reuben G. Jones synthesis of 2-hydroxypyrazines

• Pierre Legrand and
• Yves L. Janin

Beilstein J. Org. Chem. 2022, 18, 935–943, doi:10.3762/bjoc.18.93

• . Moreover, since no detectable transformations took place when quenching the reaction at −78 °C (at least after three hours when using phenylglyoxal and phenylalanine amide), the reactions were always allowed to warm to room temperature by removal of the dry ice bath. In all our trials, the two isomers 3

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• generated phosphinimines 218 followed by quenching with water and sequential loss of two molecules of dimethylamine. However, the mechanism of this transformation was not clearly investigated (Scheme 35) [16]. To develop new antitumor agents composed of chromene and 5-oxo-1,2-azaphospolidine 2-oxide motifs

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• an O2 molecule, as in the case of the COX-like mechanism. However, the radical quenching at C26 is achieved by reductants such as ascorbate, but not by Tyr224, in the final step of the reaction. CarC-like mechanism of FtmOx1 In 2019, Bollinger and co-workers reported a detailed mechanistic study

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

• -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

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

• 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

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

• 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

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

• 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

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

• 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

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

• 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

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

• (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

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

• +, 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