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

Heck- and Suzuki-coupling approaches to novel hydroquinone inhibitors of calcium ATPase

  • Robert J. Kempton,
  • Taylor A. Kidd-Kautz,
  • Soizic Laurenceau and
  • Stefan Paula

Beilstein J. Org. Chem. 2019, 15, 971–975, doi:10.3762/bjoc.15.94

Graphical Abstract
  • silfen [11]. Alkylation of 4 under typical Friedel–Crafts conditions gave 5. In the case of 5a, the 1H NMR of the crude product, while clearly showing that it was the desired 4-substituted isomer (1H singlets at δ 6.89 and 7.02), also exhibited an impurity (doublets at δ 6.83 and 7.12, J = 3.0 Hz
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Published 24 Apr 2019

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

  • Jan Hendrik Lang and
  • Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

Graphical Abstract
  • quantitative yield, albeit as mixtures of inseparable diastereomers (4:1), as consequence of the optical impurity of 22. Only when following the coupling order shown in Scheme 5, high yields could be obtained. The labile carboxylic acid 29 was formed by saponification of methyl ester 7 (LiOH, H2O/MeOH) and
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Published 28 Feb 2019

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

  • Anne Schnell,
  • J. Alexander Willms,
  • S. Nozinovic and
  • Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

Graphical Abstract
  • and the organic layer was washed six times with a 2:1 mixture of deionized water/methanol (6 × 40 mL). The aqueous layer was evaporated to yield 17 mg of a light pink solid. The 1H NMR, 31P NMR and ESIMS spectra show an impurity of triphenylphosphine oxide in the product, which does not interfere with
  • the ESIMS experiment in which 4∙Br was used as the charge-tagged substrate. Yield: 17 mg (0.03 mmol, ≈27% including impurity), 1H NMR (400 MHz, CDCl3, 298 K) δ [ppm] 8.54–8.52 (m, 2H, H-4), 8.26–8.24 (m, 2H, H-9), 7.88–7.84 (m, 6H, H-14), 7.78–7.75 (m, 3H, H-16), 7.69–7.58 (m, 9H, 6H of the 9H
  • correlate to H-15, rest correlates to impurity of POPh3), 7.55–7.52 (m, 2H, H-3), 7.48–7.45 (m, 1H, H-11), 7.40–7.37 (m, 2H, H-10), 5.85 (d, 2H, H-1); 13C{1H} NMR (126 MHz, CDCl3, 298 K) δ [ppm] 164.0 (C-6), 163.6 (C-7), 135.1 or 135.1 (C 13), 134.8 (C-14), 134.7 (C-16), 132.8 or 132.8 or 132.8 (C-5 and C-8
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Published 03 Jan 2019

A challenging redox neutral Cp*Co(III)-catalysed alkylation of acetanilides with 3-buten-2-one: synthesis and key insights into the mechanism through DFT calculations

  • Andrew Kenny,
  • Alba Pisarello,
  • Arron Bird,
  • Paula G. Chirila,
  • Alex Hamilton and
  • Christopher J. Whiteoak

Beilstein J. Org. Chem. 2018, 14, 2366–2374, doi:10.3762/bjoc.14.212

Graphical Abstract
  • reaction outcome demonstrates that the acetanilide environment is more challenging to convert than the corresponding benzamide environment. Indeed, the purified reaction product predominantly contains the benzamide substituted product 3q, with traces of impurity which is proposed to be the acetanilide
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Published 10 Sep 2018

15N-Labelling and structure determination of adamantylated azolo-azines in solution

  • Sergey L. Deev,
  • Alexander S. Paramonov,
  • Tatyana S. Shestakova,
  • Igor A. Khalymbadzha,
  • Oleg N. Chupakhin,
  • Julia O. Subbotina,
  • Oleg S. Eltsov,
  • Pavel A. Slepukhin,
  • Vladimir L. Rusinov,
  • Alexander S. Arseniev and
  • Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

Graphical Abstract
  • -alkylation in 1,2,4-triazolo[5,1-c][1,2,4]triazin-7-ones are indicated by arrows. 1D 15N NMR spectra of 30–70 mM 13-15N2, 15a,b-15N2, 20-15N2, 21a,b-15N2, 23-15N2 and 24-15N2 in DMSO-d6 (45 °C). The signal of the impurity (a base formed from salt 19-15N2 in acidic medium) is marked by an asterisk. Signals of
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Published 29 Nov 2017

Is the tungsten(IV) complex (NEt4)2[WO(mnt)2] a functional analogue of acetylene hydratase?

  • Matthias Schreyer and
  • Lukas Hintermann

Beilstein J. Org. Chem. 2017, 13, 2332–2339, doi:10.3762/bjoc.13.230

Graphical Abstract
  • an impurity in the starting alkyne 4, but may also be formed under the reaction conditions if the latter contains autoxidation impurities. Kugelrohr vacuum distillation of 4 reduced the aldehyde level to below 0.3% (Table 1, entries 5–8). Even if technically unsatisfactory, entries 3 and 4 are
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Published 02 Nov 2017

Curcuminoid–BF2 complexes: Synthesis, fluorescence and optimization of BF2 group cleavage

  • Henning Weiss,
  • Jeannine Reichel,
  • Helmar Görls,
  • Kilian Rolf Anton Schneider,
  • Mathias Micheel,
  • Michael Pröhl,
  • Michael Gottschaldt,
  • Benjamin Dietzek and
  • Wolfgang Weigand

Beilstein J. Org. Chem. 2017, 13, 2264–2272, doi:10.3762/bjoc.13.223

Graphical Abstract
  • –h in yields ranging from 56 to 96% (Table 1). The amount of base required have to be increased from 0.1 to ca. 0.6 equiv due to the formation of HF, which forms n-butylammonium fluoride as a main impurity. Therefore, all complexes were purified by recrystallization from a mixture of acetone and
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Published 26 Oct 2017

Nitration of 5,11-dihydroindolo[3,2-b]carbazoles and synthetic applications of their nitro-substituted derivatives

  • Roman A. Irgashev,
  • Nikita A. Kazin,
  • Gennady L. Rusinov and
  • Valery N. Charushin

Beilstein J. Org. Chem. 2017, 13, 1396–1406, doi:10.3762/bjoc.13.136

Graphical Abstract
  • (Table 1, entry 1 and 2). However, the starting aromatic substrate is exhausted after 15 min (control by TLC), if nitrating agents are used in excess amounts. Indeed, treatment of ICZ 1a with 5 equiv of acetyl nitrate at 0 °C has resulted in the formation of compound 2a with a small impurity of
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Published 14 Jul 2017

Synthesis of oligonucleotides on a soluble support

  • Harri Lönnberg

Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134

Graphical Abstract
  • could not be entirely removed by filtration, but a precipitation of the support with Et2O was required for quantitative removal of this impurity. During the first four coupling cycles, the coupling yields gradually increased from 75 to 90%, and remained after that high (90–95%). Isolation of pure
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Published 12 Jul 2017

A concise and practical stereoselective synthesis of ipragliflozin L-proline

  • Shuai Ma,
  • Zhenren Liu,
  • Jing Pan,
  • Shunli Zhang and
  • Weicheng Zhou

Beilstein J. Org. Chem. 2017, 13, 1064–1070, doi:10.3762/bjoc.13.105

Graphical Abstract
  • yield was 52% in three steps and the product purity was excellent. Two key diastereomers were prepared with efficient and direct access to the α-C-arylglucoside. Keywords: arylzinc derivative; β-C-arylglucoside; diastereomer impurity; ipragliflozin L-proline; stereoselective synthesis; Introduction
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Published 01 Jun 2017

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

  • Chinmay A. Shukla and
  • Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

Graphical Abstract
  • information in terms of the desired conversion, selectivity, impurity profiling), real-time integration with the process analytical tools and decision-making protocols for identifying the next set of conditions needed to move in the direction that leads to optimal performance (objective function). While these
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Published 19 May 2017

Total synthesis of TMG-chitotriomycin based on an automated electrochemical assembly of a disaccharide building block

  • Yuta Isoda,
  • Norihiko Sasaki,
  • Kei Kitamura,
  • Shuji Takahashi,
  • Sujit Manmode,
  • Naoko Takeda-Okuda,
  • Jun-ichi Tamura,
  • Toshiki Nokami and
  • Toshiyuki Itoh

Beilstein J. Org. Chem. 2017, 13, 919–924, doi:10.3762/bjoc.13.93

Graphical Abstract
  • product was purified by silica gel chromatography (hexane/EtOAc 1:1 as eluent). The precursor 7 was obtained in 49% yield (411 mg) together with building block 4 as an impurity. Further purification by GPC (CHCl3 as eluent) afforded 7 in 41% yield (328 mg, 0.178 mmol). Inhibitors of glucosaminidases
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Published 16 May 2017

Characterization of the synthetic cannabinoid MDMB-CHMCZCA

  • Carina Weber,
  • Stefan Pusch,
  • Dieter Schollmeyer,
  • Sascha Münster-Müller,
  • Michael Pütz and
  • Till Opatz

Beilstein J. Org. Chem. 2016, 12, 2808–2815, doi:10.3762/bjoc.12.279

Graphical Abstract
  • ); mp 171.5–172.4 °C; ESIMS m/z: 457.3 (19.9%, [M + Na]+), 435.4 (100%, [M + H]+), 290.3 (6.3%, fragment); HRMS-ESI m/z: calculated for [C27H35N2O3 + H]+, 435.2648; found, 435.2654; [α]D25 +38.6° (c 0.87, CDCl3). A small impurity in the sample appears in the COSY experiment (δH = 3.09 and 1.40 ppm, see
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Published 21 Dec 2016

Development of a continuous process for α-thio-β-chloroacrylamide synthesis with enhanced control of a cascade transformation

  • Olga C. Dennehy,
  • Valérie M. Y. Cacheux,
  • Benjamin J. Deadman,
  • Denis Lynch,
  • Stuart G. Collins,
  • Humphrey A. Moynihan and
  • Anita R. Maguire

Beilstein J. Org. Chem. 2016, 12, 2511–2522, doi:10.3762/bjoc.12.246

Graphical Abstract
  • of the reaction, principally to minimize the extent of impurity formation due to over-reaction. The shortest possible effective residence time would be also preferable for larger scale operation in order to maximize the reactor throughput. The dichloride intermediate 5 was still present after a 2 min
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Published 24 Nov 2016

Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins

  • Laszlo Jicsinszky,
  • Marina Caporaso,
  • Katia Martina,
  • Emanuela Calcio Gaudino and
  • Giancarlo Cravotto

Beilstein J. Org. Chem. 2016, 12, 2364–2371, doi:10.3762/bjoc.12.230

Graphical Abstract
  • drug targeting hosts [7][8], can be problematic as they require sophisticated, efficient and yet simple methods which lead to acceptable purity and impurity profiles. Furthermore, the special structural properties of selectively substituted CDs mean that their syntheses are not always environmentally
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Published 10 Nov 2016

Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties

  • Pierre Boufflet,
  • Sebastian Wood,
  • Jessica Wade,
  • Zhuping Fei,
  • Ji-Seon Kim and
  • Martin Heeney

Beilstein J. Org. Chem. 2016, 12, 2150–2163, doi:10.3762/bjoc.12.205

Graphical Abstract
  • whether these two transitions indicate phase separation and therefore separate melting transitions for each block, or are simply due to the residual P3OT impurity. However, the low melting enthalpies of both peaks and the lower melt onset of the F-P3OT block suggests that crystallization is frustrated
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Published 10 Oct 2016

A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki–Miyaura cross-coupling reaction

  • Dariusz Błachut,
  • Joanna Szawkało and
  • Zbigniew Czarnocki

Beilstein J. Org. Chem. 2016, 12, 835–845, doi:10.3762/bjoc.12.82

Graphical Abstract
  • efficient techniques (preparative HPLC). The library of synthesized compounds will be used as a reference standard during our study on impurity markers in illegally produced amphetamine analogues. In several cases of ortho-aryl-substituted pyridines, stable atropisomers were observed and this phenomenon
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Published 28 Apr 2016

Nucleic acids through condensation of nucleosides and phosphorous acid in the presence of sulfur

  • Tuomas Lönnberg

Beilstein J. Org. Chem. 2016, 12, 670–673, doi:10.3762/bjoc.12.67

Graphical Abstract
  • buffer (pH 7.0). The tall peak eluting at 1.5 min in chromatogram C corresponds to either the enzyme itself or an impurity in the commercial preparation. Phosphitylation and subsequent dimerization of thymidine. Supporting Information Supporting Information File 54: Experimental methods, HPLC
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Published 11 Apr 2016

Spiro-fused carbohydrate oxazoline ligands: Synthesis and application as enantio-discrimination agents in asymmetric allylic alkylation

  • Jochen Kraft,
  • Martin Golkowski and
  • Thomas Ziegler

Beilstein J. Org. Chem. 2016, 12, 166–171, doi:10.3762/bjoc.12.18

Graphical Abstract
  • (Scheme 2). It is noteworthy that the low yield (32%) of 10a is due to the instability of its spiro-fused oxazoline moiety during chromatography on silica gel but not to any unwanted side reactions during the cross coupling. Even small traces of HCl usually present in CDCl3 as impurity resulted in full
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Published 29 Jan 2016

Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

  • Hans Sterckx,
  • Johan De Houwer,
  • Carl Mensch,
  • Wouter Herrebout,
  • Kourosch Abbaspour Tehrani and
  • Bert U. W. Maes

Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16

Graphical Abstract
  • drug Mefloquine. The oxidation method can also be used to prepare metabolites of APIs which is illustrated for the natural product papaverine. ICP–MS analysis of the purified reaction products revealed that the base metal impurity was well below the regulatory limit. Keywords: base metal; benzylic
  • , materials) it is of vital importance to control and determine any metal impurity in the reaction product. In case the selected purification methods proved insufficient to get the metal contaminations below the maximum allowed threshold value set for active ingredients (AIs), an extra treatment might be
  • papaveraldine a comparison between different purification procedures was performed in order to determine their influence on the amount of metal impurity remaining. While the reaction is compatible with a large number of solvents including sustainable ones, DMSO appears to give the fastest reactions. This is
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Published 27 Jan 2016

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

  • Zhan-Jiang Zheng,
  • Ding Wang,
  • Zheng Xu and
  • Li-Wen Xu

Beilstein J. Org. Chem. 2015, 11, 2557–2576, doi:10.3762/bjoc.11.276

Graphical Abstract
  • the CuAAC reaction, the 5,5'-bitriazoles were usually considered as an undesired side product or impurity in the Huisgen cycloaddition. In general, they are the oxidative coupling product of the triazole-copper species. The 5,5'-bitriazoles were usually formed as the major product by the facilitation
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Published 11 Dec 2015

Two strategies for the synthesis of the biologically important ATP analogue ApppI, at a multi-milligram scale

  • Janne Weisell,
  • Jouko Vepsäläinen and
  • Petri A. Turhanen

Beilstein J. Org. Chem. 2015, 11, 2189–2193, doi:10.3762/bjoc.11.237

Graphical Abstract
  • any NMR characterization data, only HPLC and MS data were presented, and these are rather unsatisfactory methods with which to prove the purity of a product. They also stated that there was 5–10% ADP (adenosine diphosphate) as an impurity in some preparations and that it is possible that there may
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Published 13 Nov 2015

Reactions of nitroxides 15. Cinnamates bearing a nitroxyl moiety synthesized using a Mizoroki–Heck cross-coupling reaction

  • Jerzy Zakrzewski and
  • Bogumiła Huras

Beilstein J. Org. Chem. 2015, 11, 1155–1162, doi:10.3762/bjoc.11.130

Graphical Abstract
  • ), 2.37 (s, 3H, CH3), 5.23 (tt, J = 11.1 Hz, J = 4.4 Hz, 1H, CH-OC(=O)), 6.35 (d, J = 15.8 Hz, 1H, Ar-CH=CH-COO), 7.64 (d, J = 15.8 Hz, 1H, Ar-CH=CH-COO); 13C NMR (50 MHz, δ, CDCl3, TMS, PhNHNH2): 21.35 (impurity), 21.69 (2×CH3), 23.04 (ArCH3), 29.84 (2×CH3), 43.01 (2×CH2), 62.60 (2×C(CH3)2), 65.67 (CH-O
  • -), 115.32 (impurity), 117.03 (CH), 128.34 (CH), 129.86 (CH), 141.12 (C), 145.37 (CH), 166.73 (C=O), 179.47 (impurity); IR (cm−1, film): 2976, 1711, 1635, 1166, 815. 2,2,6,6-Tetramethyl-1-oxyl-4-piperidyl 3-E-(3,4-dichlorophenyl)acrylate (5c) 62.7%; pink crystals, mp 118–120 °C; MS (EI, 70 eV, m/z, int
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Published 13 Jul 2015

Synthesis of dinucleoside acylphosphonites by phosphonodiamidite chemistry and investigation of phosphorus epimerization

  • William H. Hersh

Beilstein J. Org. Chem. 2015, 11, 184–191, doi:10.3762/bjoc.11.19

Graphical Abstract
  • )thymidine, and separation of this alcohol impurity from the acyl dinucleosides could not be achieved. The characterization of the acyl dinucleosides was accomplished by 1D and 2D 1H and 13C NMR spectra, with confirmation of the dinucleoside structures by high-resolution positive ion ESI mass spectrometry
  • , as is seen for the parent alcohols [31]. For 12, this analysis could not be carried out with as much certainty due to the larger amount of the 3′-O-tert-butyldimethylsilyl thymidine impurity. As previously observed for the β-cyanoethoxy dithymidyl triesters [31], the characteristic two pairs of
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Published 30 Jan 2015

Efficient deprotection of F-BODIPY derivatives: removal of BF2 using Brønsted acids

  • Mingfeng Yu,
  • Joseph K.-H. Wong,
  • Cyril Tang,
  • Peter Turner,
  • Matthew H. Todd and
  • Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 37–41, doi:10.3762/bjoc.11.6

Graphical Abstract
  • analysis indicated that this impurity was present at ≤5% abundance, but HPLC purification was required to generate analytically pure 18 which compromised the final yields (53% for both methods). We are aware of two previous reports investigating the treatment of BODIPYs with Brønsted acids. Yang et al
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Published 09 Jan 2015
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