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Search for "impurity" in Full Text gives 72 result(s) in Beilstein Journal of Organic Chemistry.

Synthetic approach to borrelidin fragments: focus on key intermediates

  • Yudhi Dwi Kurniawan,
  • Zetryana Puteri Tachrim,
  • Teni Ernawati,
  • Faris Hermawan,
  • Ima Nurasiyah and
  • Muhammad Alfin Sulmantara

Beilstein J. Org. Chem. 2025, 21, 1135–1160, doi:10.3762/bjoc.21.91

Graphical Abstract
  • simple impurity removal from the key chiral intermediates through recrystallization, from which their exact structures could be elucidated by XRD crystallography. Zhou’s approach for constructing Omura’s C3–C11 fragment In 2018, Zhou and co-workers developed an efficient, high-yielding iterative
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Published 12 Jun 2025

Unprecedented visible light-initiated topochemical [2 + 2] cycloaddition in a functionalized bimane dye

  • Metodej Dvoracek,
  • Brendan Twamley,
  • Mathias O. Senge and
  • Mikhail A. Filatov

Beilstein J. Org. Chem. 2025, 21, 500–509, doi:10.3762/bjoc.21.37

Graphical Abstract
  • purification, the 1H NMR of Cl2B showed 6% of an impurity, possibly the anti-isomer. Further purification of Cl2B reduced the impurity content to less than 3%. Topochemical photocycloaddition Upon examining the crystal structure of our first sample of Cl2B, Cl2B (A), we observed that the compound had undergone
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Published 05 Mar 2025

Identification and removal of a cryptic impurity in pomalidomide-PEG based PROTAC

  • Bingnan Wang,
  • Yong Lu and
  • Chuo Chen

Beilstein J. Org. Chem. 2025, 21, 407–411, doi:10.3762/bjoc.21.28

Graphical Abstract
  • impurity generated in this process. Nucleophilic acyl substitution competes with aromatic substitution to displace glutarimide and gives a byproduct that can co-elute with the desired product on HPLC throughout the remainder of the synthesis. Scavenging with taurine is a convenient way to minimize this
  • contamination. Keywords: glutarimide; IMiD; impurity; nucleophilic acyl substitution; PROTAC; Introduction Targeted protein degradation capitalizing on the concept of chemically induced dimerization has emerged as a new therapeutic approach recently [1]. In particular, the modularity of proteolysis targeting
  • shoulder peak (Figure 2, marked with asterisk). A close examination of the UV profile indicated the presence of an impurity. Its removal requires repetitive prep-HPLC purifications that are inefficient and time-consuming. The isolated impurity lacks the characteristic fluorescent yellow color of
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Published 18 Feb 2025

Emerging trends in the optimization of organic synthesis through high-throughput tools and machine learning

  • Pablo Quijano Velasco,
  • Kedar Hippalgaonkar and
  • Balamurugan Ramalingam

Beilstein J. Org. Chem. 2025, 21, 10–38, doi:10.3762/bjoc.21.3

Graphical Abstract
  • to maximize the space–time yield (STY) while minimizing either the E-factor of the SNAr reaction or the impurity concentration of the N-benzylation reaction. For both reactions, there were four variables to optimize, including metrics for reaction time, reagent concentration, and temperature. After
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Published 06 Jan 2025

C–H Trifluoromethylthiolation of aldehyde hydrazones

  • Victor Levet,
  • Balu Ramesh,
  • Congyang Wang and
  • Tatiana Besset

Beilstein J. Org. Chem. 2024, 20, 2883–2890, doi:10.3762/bjoc.20.242

Graphical Abstract
  • (0.4 M), 20 °C, 10 min; then, AgSCF3 (0.6 mmol, 2.0 equiv), under argon. Isolated yields are given. aProducts 4a and 5a were isolated with an inseparable impurity. bReaction performed at 0 °C for the 1st step, and 20 °C for the 2nd one. Scope of the reaction. Reaction conditions: 1 (0.3 mmol, 1.0 equiv
  • ), NBS (0.33 mmol, 1.1 equiv) in CH3CN (0.4 M), 20 °C, 10 min; then, AgSCF3 (0.6 mmol, 2.0 equiv), 2 h, under argon. a0.15 mmol reaction scale. bProduct 2v was isolated with an inseparable impurity. Mechanistic investigations and post-functionalization reactions. a19F NMR yields using α,α,α
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Published 12 Nov 2024

Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives

  • Tural N. Akhmedov,
  • Ajeet Kumar,
  • Daken J. Starkenburg,
  • Kyle J. Chesney,
  • Khalil A. Abboud,
  • Novruz G. Akhmedov,
  • Jiangeng Xue and
  • Ronald K. Castellano

Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92

Graphical Abstract
  • building blocks 1,2-aceanthrylenedione and 12, as detailed in Table S1 (Supporting Information File 1). However, an inseparable unknown impurity was observed along with the desired product 3a in all cases when analyzed by 1H NMR. Under strict temperature and time control (80 °C for 72 hours) using 2.5
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Published 08 May 2024

Spin and charge interactions between nanographene host and ferrocene

  • Akira Suzuki,
  • Yuya Miyake,
  • Ryoga Shibata and
  • Kazuyuki Takai

Beilstein J. Org. Chem. 2024, 20, 1011–1019, doi:10.3762/bjoc.20.89

Graphical Abstract
  • to the more significant carrier scattering by introducing FeCp2 as a positively charged impurity caused by charge transfer with nanographene in FeCp2-ACFs-150. This is also supported by the increase in the linewidth of the G-band from 28 cm−1 (ACFs) to 31 cm−1 (FeCp2-ACFs-150). Figure 5 shows IR
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Published 02 May 2024

Synthesis and characterization of water-soluble C60–peptide conjugates

  • Yue Ma,
  • Lorenzo Persi and
  • Yoko Yamakoshi

Beilstein J. Org. Chem. 2024, 20, 777–786, doi:10.3762/bjoc.20.71

Graphical Abstract
  • by reversed-phase HPLC. C60–oligo-Glu (5b), which was soluble only in basic aqueous solution, could not be isolated by HPLC, especially in the presence of an oligo-Glu impurity, and was purified only after spin filtration. C60–oligo-Arg (5c) was not soluble in any solvent and could not be further
  • –peptide conjugate 5a in D2O (above) and of the precursor monoadduct in CDCl3 (bottom) at 600 MHz. 13C NMR spectrum of C60–peptide conjugate 5a in D2O and of the precursor monoadduct in CDCl3 at 150 MHz (a) and expansion of the sp2 carbon region (b). The asterisks in (a) correspond to a TFA impurity
  • crude sample of 5b, with the penta-Glu impurity being soluble in pyridine-d5 (Figures S13–S17, Supporting Information File 1). a) X-band ESR spectra of the 4-oxo-TEMP adduct with 1O2 generated by C60–oligo-Lys (5a) and rose bengal (RB), respectively, in aqueous solutions under irradiation with a green
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Published 12 Apr 2024

Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

  • Ekaterina V. Kolupaeva,
  • Narek A. Dzhangiryan,
  • Alexander F. Pozharskii,
  • Oleg P. Demidov and
  • Valery A. Ozeryanskii

Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24

Graphical Abstract
  • positions 5 and 8 already at room temperature (Scheme 3). The overall yield of the main product 10 turned out to be high, but the substance contained a hard-to-separate impurity in an amount of up to 12%, to which, judged by the high-field position of the signals in the corresponding proton spectrum, was
  • assigned the structure of the intermediate mononitro derivative 11 (Supporting Information File 1, Figure S2). Hoping to avoid formation of the “mononitro derivative” impurity, we increased the reaction time, the amount and composition of the nitrating mixture, and the temperature, but according to the
  • results of 1H NMR spectra and TLC analysis, the second component was still present. This “permanent impurity” cannot be separated by chromatography or recrystallization, but it can be eliminated to some extent by washing the nitration products with hot chloroform, in which the impurity is slightly better
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Published 08 Feb 2024

Synthesis of the 3’-O-sulfated TF antigen with a TEG-N3 linker for glycodendrimersomes preparation to study lectin binding

  • Mark Reihill,
  • Hanyue Ma,
  • Dennis Bengtsson and
  • Stefan Oscarson

Beilstein J. Org. Chem. 2024, 20, 173–180, doi:10.3762/bjoc.20.17

Graphical Abstract
  • , led to isolation of a mixture of 2 and a tin-related impurity (n-butyl chain evident by NMR). Acetylation of this material followed by flash chromatography proved ineffective in removing the unwanted entity. To overcome this problem, flash chromatography was performed before stirring with the ion
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Published 30 Jan 2024

Unprecedented synthesis of a 14-membered hexaazamacrocycle

  • Anastasia A. Fesenko and
  • Anatoly D. Shutalev

Beilstein J. Org. Chem. 2023, 19, 1728–1740, doi:10.3762/bjoc.19.126

Graphical Abstract
  • , according to NMR spectroscopic data, the isolated product was a mixture of the desired macrocycle 5 and a noticeable amount of an impurity (Scheme 2) whose formation was not mentioned in the cited reference. The structure of the concomitant impurity was established using 1D and 2D NMR spectroscopy. The 1H
  • = 11.2 Hz), four NH2 groups at 6.27, 5.72, 5.59, and 4.61 ppm (singlets). Signals of 11 different carbon atoms including 8 carbons of two methylpyrazole moieties were observed in the 13С NMR spectrum. Thus, we concluded that the impurity has bis-pyrazole structure 6. This structure was also confirmed by
  • -standard approach [44] (see the Supporting Information File 1 for details). The high-resolution mass spectrum (ESI+) of a mixture of 5 and the impurity, in addition to a peak at m/z = 329.1696 [M + H]+ for compound 5, shows a peak at m/z = 319.1862 [M + H]+, consistent with the molecular formula of
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Published 15 Nov 2023

Radical chemistry in polymer science: an overview and recent advances

  • Zixiao Wang,
  • Feichen Cui,
  • Yang Sui and
  • Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

Graphical Abstract
  • -defined and high-molecular-weight polymers. PVC, PS, and poly(methyl methacrylate) (PMMA) are industrially produced through suspension polymerization [2]. Nonetheless, the Trommsdorff–Norrish effect exists in suspension polymerization processes, and the residual suspending agent becomes an impurity
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Published 18 Oct 2023

Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

  • Louis Monsigny,
  • Floriane Doche and
  • Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

Graphical Abstract
  • on aliphatic amide derivatives derived from 8-aminoquinoline by palladium-catalyzed C–H bond activation described by Besset and co-workers [126]. Product 32d was contaminated with 10% of an inseparable impurity. Regio- and diastereoselective difluoromethylthiolation of acrylamides under palladium
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Published 17 Apr 2023

Recommendations for performing measurements of apparent equilibrium constants of enzyme-catalyzed reactions and for reporting the results of these measurements

  • Robert N. Goldberg,
  • Robert T. Giessmann,
  • Peter J. Halling,
  • Carsten Kettner and
  • Hans V. Westerhoff

Beilstein J. Org. Chem. 2023, 19, 303–316, doi:10.3762/bjoc.19.26

Graphical Abstract
  • present as an impurity in most substances and since weighing is often used to determine the amounts of substances, the moisture content of the principal substances used in a study should be reported. If the moisture content is important and can vary, one should report the method used to control and
  • in a suspension or solution, that an impurity in the enzyme suspension or solution does not interfere with the measurement. Thus, when a spectroscopic method is used for an equilibrium measurement (e.g., in an NAD/NADH coupled reaction), it has been customary to perform a control experiment in which
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Published 15 Mar 2023

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

Graphical Abstract
  • analysis to control the acid concentration. Good extraction efficiency and purification were achieved for an amine as a test substrate that was contaminated with a minor impurity. Remaining challenges such as time-consuming optimization and the need for several pumps can be overcome through careful
  • impurity might also contain the same functional group that has affinity to the resin (Scheme 10). QP-SA is a commonly used resin which contains –SO3H groups and can sequester amines, whereby a solution of ammonia in MeOH can be used to release the product [94]. Amine-functionalized resins like A-900 can be
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Published 16 Dec 2022

Complementarity of solution and solid state mechanochemical reaction conditions demonstrated by 1,2-debromination of tricyclic imides

  • Petar Štrbac and
  • Davor Margetić

Beilstein J. Org. Chem. 2022, 18, 746–753, doi:10.3762/bjoc.18.75

Graphical Abstract
  • , small amounts of another cycloadduct were obtained. It was found that this is the product arising from anthraquinone (32), which was present as an impurity in 31. Independent milling of 10 with anthraquinone afforded dihydroxy cycloadduct 33 (in 35% yield) indicating that in the reaction conditions of
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Published 24 Jun 2022

Synthesis and late stage modifications of Cyl derivatives

  • Phil Servatius and
  • Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

Graphical Abstract
  • as impurity, which could not be separated from the product. Subsequent hydrogenation proceeded readily and afforded the saturated cyclopeptide 13. However, the impurity could also not be removed on this stage. Apparently, the Cyl derivatives with a short side chain are not good candidates for further
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Published 04 Feb 2022

Efficient and regioselective synthesis of dihydroxy-substituted 2-aminocyclooctane-1-carboxylic acid and its bicyclic derivatives

  • İlknur Polat,
  • Selçuk Eşsiz,
  • Uğur Bozkaya and
  • Emine Salamci

Beilstein J. Org. Chem. 2022, 18, 77–85, doi:10.3762/bjoc.18.7

Graphical Abstract
  • with NaHSO4 in a mixture of methylene chloride/MeOH proceeded as described in Scheme 5. First, the C=O group of the ester prefers to attack the protonated epoxide to give intermediate 15. Then, water, which is available in methanol as an impurity, attacks the oxonium ion to give dealkylation product 10
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Published 06 Jan 2022

Synthesis of bis(aryloxy)fluoromethanes using a heterodihalocarbene strategy

  • Carl Recsei and
  • Yaniv Barda

Beilstein J. Org. Chem. 2021, 17, 813–818, doi:10.3762/bjoc.17.70

Graphical Abstract
  • , we completed the radical bromination of 4 to produce 3 (Scheme 5), which was used to deliver the penultimate bis-thioether 2, with oxidation to 1 giving the target impurity structure as anticipated, with a combined yield for the three transformations from 4 to 1 of 42%. The synthesis of 4 was also
  • applications. Conclusion We have synthesized the trace impurity 1, using a novel and operationally simple procedure for the construction of acyclic bis(aryloxy)fluoromethanes and extended the transformation to two representative electron-poor phenols. We were able to provide preliminary answers to the
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Published 12 Apr 2021

Coupling biocatalysis with high-energy flow reactions for the synthesis of carbamates and β-amino acid derivatives

  • Alexander Leslie,
  • Thomas S. Moody,
  • Megan Smyth,
  • Scott Wharry and
  • Marcus Baumann

Beilstein J. Org. Chem. 2021, 17, 379–384, doi:10.3762/bjoc.17.33

Graphical Abstract
  • flow process is presented that couples a Curtius rearrangement step with a biocatalytic impurity tagging strategy to produce a series of valuable Cbz-carbamate products. Immobilized CALB was exploited as a robust hydrolase to transform residual benzyl alcohol into easily separable benzyl butyrate. The
  • ) via a T-piece with the flow stream exiting the scavenger column (A15/A21). The combined stream was then directed into an Omnifit column (10 cm length, 6.6 mm i.d.) containing immobilized CALB (tRes ca. 2–5 min; rt). The flow set-up for the CALB-mediated impurity tagging approach is depicted in Scheme
  • carbamate group allowing for further use of the resulting N-protected amino acid species (e.g., 9d) in synthetic elaborations. Conclusion In conclusion, a new strategy in continuous flow processing that combines challenging high-energy transformations with downstream impurity tagging facilitated by
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Published 04 Feb 2021

Novel library synthesis of 3,4-disubstituted pyridin-2(1H)-ones via cleavage of pyridine-2-oxy-7-azabenzotriazole ethers under ionic hydrogenation conditions at room temperature

  • Romain Pierre,
  • Anne Brethon,
  • Sylvain A. Jacques,
  • Aurélie Blond,
  • Sandrine Chambon,
  • Sandrine Talano,
  • Catherine Raffin,
  • Branislav Musicki,
  • Claire Bouix-Peter,
  • Loic Tomas,
  • Gilles Ouvry,
  • Rémy Morgentin,
  • Laurent F. Hennequin and
  • Craig S. Harris

Beilstein J. Org. Chem. 2021, 17, 156–165, doi:10.3762/bjoc.17.16

Graphical Abstract
  • degradation with the dominant impurity coming from cleavage of the amide bond (Table 3, entry 2) and dissolving metal reduction conditions using zinc were quickly excluded as just 30% conversion was achieved with the added work-up complications (Table 3, entry 3). Finally and rather fortuitously, we turned
  • a trifluoroacetamide impurity, presumably forming by reaction with the cyclohexylamine moiety. In the absence of triethylsilane (TES), only deprotection of the Boc group was observed when using TFA (Table 3, entry 8) and when the reaction was carried out in mixture of TFA/H2O (4:1) over 4 days, only
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Published 18 Jan 2021

Synthetic terpenoids in the world of fragrances: Iso E Super® is the showcase

  • Alexey Stepanyuk and
  • Andreas Kirschning

Beilstein J. Org. Chem. 2019, 15, 2590–2602, doi:10.3762/bjoc.15.252

Graphical Abstract
  • original patent [15]. An impurity of ca. 5%, now called Iso E Super Plus® (34), was made responsible for the characteristic smell having an odour threshold as low as 5 ng L−1 [23]. Naturally, this impurity was thoroughly analysed in the laboratories of Givaudan SA and finally secured in a patent as Iso E
  • Super Plus® (34). Later, also the second impurity Georgywood® (35) with a higher odour threshold of 15 to 30 ng L−1 but better odour characteristics was patented [17][18][19][20]. Further details on the individual components of this complex mixture are listed in Table 1. It must be noted that the
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Published 31 Oct 2019

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

  • Thines Kanagasundaram,
  • Antje Timmermann,
  • Carsten S. Kramer and
  • Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

Graphical Abstract
  • optimizations of the reaction conditions could lead to the silicon rhodamine 22 in moderate yields, an inseparable impurity of the cationic fluorophore was detected. After identifying this impurity as the tetraphenylphosphonium cation, we exchanged the triphenylphosphine ligand of the catalyst with dppf (1,1
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Published 29 Oct 2019

An azobenzene container showing a definite folding – synthesis and structural investigation

  • Abdulselam Adam,
  • Saber Mehrparvar and
  • Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

Graphical Abstract
  • -layer plates. Flash chromatography was carried out on silica gel 60 (230–400 mesh). 1H and 13C NMR spectra were measured with an Avance HD 600 spectrometer. All chemical shifts (δ) are given in ppm. The spectra were referenced to the peak for the protium impurity in the deuterated solvents indicated in
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Published 10 Jul 2019

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

  • Sagarika Samantray,
  • Sreenivasulu Bandi and
  • Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

Graphical Abstract
  • AgI was removed by filtration. Following this procedure, the presence of iodide as impurity could not be ruled out but its presence was found to not influence the formation of the targeted complex. In contrast, the presence of chloride remaining as impurity when PdCl2 was reacted with AgY to prepare
  • as BF4−, ClO4− and OTf− are not accommodated in the cavities and not helpful as templates. The Pd(NO3)2 sample prepared from PdCl2 and AgNO3, contained chloride as impurity and resulted in a mixture of products along with the targeted 4a (Supporting Information File 1, Figure S35b). The products in
  • the mixture were identified as [(Cl)(NO3)@Pd3(L1)4](NO3)4 (6a’) and [(Cl)2@Pd3(L1)4](NO3)4 (6a) and their proportion was found to depend on the amount of chloride as impurity. The influence of chloride on the product composition is discussed in a later section. The complex 4a was characterized by
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Published 21 May 2019
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