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12 article(s) from König, Burkhard

Azologization of serotonin 5-HT₃ receptor antagonists

Karin Rustler,
Galyna Maleeva,
Piotr Bregestovski and
Burkhard König

Full Research Paper
Published 25 Mar 2019

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1. Graphical Abstract
2. Scheme 1: Approach of the direct azologization of reported [60,61] serotonin 5-HT₃R antagonists via replacement of a...
  
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3. Scheme 2: Synthesis of the differently substituted quinoxaline azobenzene derivatives 5a and 5b via Baeyer [62]–M...
  
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4. Scheme 3: Synthesis of the methoxy-substituted quinoxaline derivative 12a via diazotization [66-69].
  
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5. Scheme 4: General procedure for the synthesis of purine- and thienopyrimidine-substituted arylazobenzenes and...
  
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6. Scheme 5: Synthesis of the thiomethyl-linked purine azobenzene 23 [62,63,72-74].
  
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7. Scheme 6: Synthesis of the amide-linked azobenzene purine 28 [62,63,75-77].
  
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8. Figure 1: UV–vis absorption spectra measured at 50 µM in DMSO. Left: purine derivative 16c; right: azo-extend...
  
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9. Figure 2: On the left panel representative traces of currents induced by the application of 3 µM 5HT (black t...
  
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Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

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Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

Amrita Das,
Mitasree Maity,
Simon Malcherek,
Burkhard König and
Julia Rehbein

Full Research Paper
Published 27 Sep 2018

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1. Graphical Abstract
2. Figure 1: Selected examples of sulfenylated heterocycles used in pharmaceuticals and material chemistry.
  
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3. Scheme 1: Synthetic routes to organosulfur compounds.
  
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4. Scheme 2: Aryl sulfide synthesis.
  
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5. Scheme 3: Substrate scope for arylthiol syntheses. The reaction was performed with 1a–g (0.1 mmol) and 2a–d (...
  
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6. Figure 2: Crystal structures of compounds 3a, 3d, 3e and 3i.
  
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7. Scheme 4: Radical trapping experiments.
  
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8. Figure 3: (a) Changes in the fluorescence spectra (in this case intensity, λ_Ex = 455 nm) of [Ir(dF(CF₃)ppy)₂(...
  
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9. Scheme 5: Proposed mechanism for visible light mediated direct C–H sulfenylation.
  
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10. Figure 4: Black line: UV–vis spectrum of the degassed [Ir] + 1,3,5-TMB mixture (solution A) in ACN. Blue and ...
  
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Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

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Photocatalytic formation of carbon–sulfur bonds

Alexander Wimmer and
Burkhard König

Review
Published 05 Jan 2018

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1. Graphical Abstract
2. Scheme 1: General overview over the sulfur-based substrates and reactive intermediates that are discussed in ...
  
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3. Scheme 2: Photoredox-catalyzed radical thiol–ene reaction, applying [Ru(bpz)₃](PF₆)₂ as photocatalyst.
  
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4. Scheme 3: Photoredox-catalyzed thiol–ene reaction of aliphatic thiols with alkenes enabled by aniline derivat...
  
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5. Scheme 4: Photoredox-catalyzed radical thiol–ene reaction for the postfunctionalization of polymers (a) and n...
  
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6. Scheme 5: Photoredox-catalyzed thiol–ene reaction enabled by bromotrichloromethane as redox additive.
  
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7. Scheme 6: Photoredox-catalyzed preparation of β-ketosulfoxides with Eosin Y as organic dye as photoredox cata...
  
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8. Scheme 7: Greaney’s photocatalytic radical thiol–ene reaction, applying TiO₂ nanoparticles as photocatalyst.
  
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9. Scheme 8: Fadeyi’s photocatalytic radical thiol–ene reaction, applying Bi₂O₃ as photocatalyst.
  
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10. Scheme 9: Ananikov’s photocatalytic radical thiol-yne reaction, applying Eosin Y as photocatalyst.
  
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11. Scheme 10: Organocatalytic visible-light photoinitiated thiol–ene coupling, applying phenylglyoxylic acid as o...
  
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12. Scheme 11: Xia’s photoredox-catalyzed synthesis of 2,3-disubstituted benzothiophenes, applying 9-mesityl-10-me...
  
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13. Scheme 12: Wang’s metal-free photoredox-catalyzed radical thiol–ene reaction, applying 9-mesityl-10-methylacri...
  
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14. Scheme 13: Visible-light benzophenone-catalyzed metal- and oxidant-free radical thiol–ene reaction.
  
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15. Scheme 14: Visible-light catalyzed C-3 sulfenylation of indole derivatives using Rose Bengal as organic dye.
  
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16. Scheme 15: Photocatalyzed radical thiol–ene reaction and subsequent aerobic sulfide-oxidation with Rose Bengal...
  
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17. Scheme 16: Photoredox-catalyzed synthesis of diaryl sulfides.
  
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18. Scheme 17: Photocatalytic cross-coupling of aryl thiols with aryl diazonium salts, using Eosin Y as photoredox...
  
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19. Scheme 18: Photocatalyzed cross-coupling of aryl diazonium salts with cysteines in batch and in a microphotore...
  
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20. Scheme 19: Fu’s [Ir]-catalyzed photoredox arylation of aryl thiols with aryl halides.
  
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21. Scheme 20: Fu’s photoredox-catalyzed difluoromethylation of aryl thiols.
  
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22. Scheme 21: C–S cross-coupling of thiols with aryl iodides via [Ir]-photoredox and [Ni]-dual-catalysis.
  
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23. Scheme 22: C–S cross-coupling of thiols with aryl bromides, applying 3,7-bis-(biphenyl-4-yl)-10-(1-naphthyl)ph...
  
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24. Scheme 23: Collin’s photochemical dual-catalytic cross-coupling of thiols with bromoalkynes.
  
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25. Scheme 24: Visible-light-promoted C–S cross-coupling via intermolecular electron donor–acceptor complex format...
  
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26. Scheme 25: Li’s visible-light photoredox-catalyzed thiocyanation of indole derivatives with Rose Bengal as pho...
  
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27. Scheme 26: Hajra’s visible-light photoredox-catalyzed thiocyanation of imidazoheterocycles with Eosin Y as pho...
  
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28. Scheme 27: Wang’s photoredox-catalyzed thiocyanation reaction of indoles, applying heterogeneous TiO₂/MoS₂ nan...
  
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29. Scheme 28: Yadav’s photoredox-catalyzed α-C(sp³)–H thiocyanation reaction for tertiary amines, applying Eosin ...
  
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30. Scheme 29: Yadav’s photoredox-catalyzed synthesis of 5-aryl-2-imino-1,3-oxathiolanes.
  
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31. Scheme 30: Yadav’s photoredox-catalyzed synthesis of 1,3-oxathiolane-2-thiones.
  
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32. Scheme 31: Li’s photoredox catalysis for the preparation of 2-substituted benzothiazoles, applying [Ru(bpy)₃](...
  
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33. Scheme 32: Lei’s external oxidant-free synthesis of 2-substituted benzothiazoles by merging photoredox and tra...
  
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34. Scheme 33: Metal-free photocatalyzed synthesis of 2-aminobenzothiazoles, applying Eosin Y as photocatalyst.
  
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35. Scheme 34: Metal-free photocatalyzed synthesis of 1,3,4-thiadiazoles, using Eosin Y as photocatalyst.
  
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36. Scheme 35: Visible-light photoredox-catalyzed preparation of benzothiophenes with Eosin Y.
  
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37. Scheme 36: Visible-light-induced KOH/DMSO superbase-promoted preparation of benzothiophenes.
  
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38. Scheme 37: Jacobi von Wangelin’s photocatalytic approach for the synthesis of aryl sulfides, applying Eosin Y ...
  
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39. Scheme 38: Visible-light photosensitized α-C(sp³)–H thiolation of aliphatic ethers.
  
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40. Scheme 39: Visible-light photocatalyzed cross-coupling of alkyl and aryl thiosulfates with aryl diazonium salt...
  
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41. Scheme 40: Visible-light photocatalyzed, controllable sulfenylation and sulfoxidation with organic thiosulfate...
  
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42. Scheme 41: Rastogi’s photoredox-catalyzed methylsulfoxidation of aryl diazonium salts, using [Ru(bpy)₃]Cl₂ as ...
  
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43. Scheme 42: a) Visible-light metal-free Eosin Y-catalyzed procedure for the preparation of vinyl sulfones from ...
  
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44. Scheme 43: Visible-light photocatalyzed cross-coupling of sodium sulfinates with secondary enamides.
  
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45. Scheme 44: Wang’s photocatalyzed oxidative cyclization of phenyl propiolates with sulfinic acids, applying Eos...
  
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46. Scheme 45: Lei’s sacrificial oxidant-free synthesis of allyl sulfones by merging photoredox and transition met...
  
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47. Scheme 46: Photocatalyzed Markovnikov-selective radical/radical cross-coupling of aryl sulfinic acids and term...
  
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48. Scheme 47: Visible-light Eosin Y induced cross-coupling of aryl sulfinic acids and styrene derivatives, afford...
  
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49. Scheme 48: Photoredox-catalyzed bicyclization of 1,7-enynes with sulfinic acids, applying Eosin Y as photocata...
  
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50. Scheme 49: Visible-light-accelerated C–H-sulfinylation of arenes and heteroarenes.
  
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51. Scheme 50: Visible-light photoredox-catalyzed β-selenosulfonylation of electron-rich olefins, applying [Ru(bpy)...
  
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52. Scheme 51: Photocatalyzed preparation of β-chlorosulfones from the respective olefins and p-toluenesulfonyl ch...
  
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53. Scheme 52: a) Photocatalyzed preparation of β-amidovinyl sulfones from sulfonyl chlorides. b) Preparation of β...
  
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54. Scheme 53: Visible-light photocatalyzed sulfonylation of aliphatic tertiary amines, applying [Ru(bpy)₃](PF₆)₂ ...
  
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55. Scheme 54: Reiser’s visible-light photoredox-catalyzed preparation of β-hydroxysulfones from sulfonyl chloride...
  
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56. Scheme 55: a) Sun’s visible-light-catalyzed approach for the preparation of isoquinolinonediones, applying [fac...
  
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57. Scheme 56: Visible-light photocatalyzed sulfonylation/cyclization of vinyl azides, applying [Ru(bpy)₃]Cl₂ as p...
  
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58. Scheme 57: Visible-light photocatalyzed procedure for the formation of β-ketosulfones from aryl sulfonyl chlor...
  
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59. Scheme 58: Zheng’s method for the sulfenylation of indole derivatives, applying sulfonyl chlorides via visible...
  
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60. Scheme 59: Cai’s visible-light induced synthesis of β-ketosulfones from sulfonyl hydrazines and alkynes.
  
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61. Scheme 60: Photoredox-catalyzed approach for the preparation of vinyl sulfones from sulfonyl hydrazines and ci...
  
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62. Scheme 61: Jacobi von Wangelin’s visible-light photocatalyzed chlorosulfonylation of anilines.
  
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63. Scheme 62: Three-component photoredox-catalyzed synthesis of N-amino sulfonamides, applying PDI as organic dye....
  
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64. Scheme 63: Visible-light induced preparation of complex sulfones from oximes, silyl enol ethers and SO₂.
  
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Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

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Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst

Martin Obst and
Burkhard König

Full Research Paper
Published 09 Nov 2016

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1. Graphical Abstract
2. Figure 1: Rod mill, schematic (left) and photographs (middle and right).
  
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3. Scheme 1: Oxidation of 4,4’-dimethoxybenzhydrol (1a) to 4,4’-dimethoxybenzophenone (1b).
  
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4. Scheme 2: Scope for benzylic alcohol oxidation and obtained yields.
  
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5. Scheme 3: Oxidation of 4-methoxyphenyl methyl carbinol (6a) to 4-methoxyacetophenone (6b).
  
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6. Figure 2: ¹H NMR (crude) of 4-methoxyacetophenone 6b.
  
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Beilstein J. Org. Chem. 2016, 12, 2358–2363, doi:10.3762/bjoc.12.229

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Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

Qiu Sun,
Jörg Heilmann and
Burkhard König

Review
Published 16 Feb 2015

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1. Graphical Abstract
2. Figure 1: Structure of 4-hydroxybenzyl alcohol (HBA, 1).
  
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3. Figure 2: Structure–activity relationship of curcumin analogs.
  
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4. Scheme 1: Synthesis of curcumin (3). Reagents and conditions: (a) vanillin, 1,2,3,4-tetrahydroquinoline, HOAc...
  
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5. Figure 3: Backbone and substitution of monocarbonyl analogs of curcumin (MACs) showing their structural diver...
  
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6. Scheme 2: Exemplary synthesis of MAC representatives. Reagents and conditions: (a) 40% KOH, EtOH, 5 °C; stirr...
  
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7. Scheme 3: Synthesis of ellagic acid (7). Reagents and conditions: (a) H₂SO₄, CH₃OH; (b) (1) o-chloranil, Et₂O...
  
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8. Figure 4: Structure of resveratrol and its analogs.
  
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9. Scheme 4: Synthesis of quinolone-substituted phenol 20. Reagents and conditions: (a) Ac₂O, 2-hydroxybenzaldeh...
  
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10. Scheme 5: Synthesis of quinolone-substituted phenol 23. Reagents and conditions: (a) Ac₂O, 2-hydroxybenzaldeh...
  
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11. Figure 5: Design of 4-amino-2-sulfanylphenol derivatives and their structure–activity relationship.
  
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12. Scheme 6: Synthesis of 4-amino-2-sulfanylphenol derivatives. Reagents and conditions: (a) R¹SO₂Cl, pyridine, ...
  
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13. Figure 6: Structures of two series of natural-like acylphloroglucinols.
  
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14. Scheme 7: Synthesis of acylphloroglucinol derivatives 35–41. Reagents and conditions: (a) acyl chloride, AlCl₃...
  
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15. Scheme 8: Synthesis of acylphloroglucinol derivatives 43–51. Reagents and conditions: (a) isoprene, Amberlyst...
  
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16. Figure 7: Analogs of (−)-EGCG for the prevention of oxidation and improvement of the bioavailability of the c...
  
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17. Scheme 9: Synthesis of xanthohumol 58. Reagents and conditions: (a) MOMCl, diisopropylethylamine, CH₂Cl₂; (b)...
  
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18. Scheme 10: Synthesis of genistein 60. Reagents and conditions: (a) 4-hydroxyphenylacetonitrile, anhydrous HCl,...
  
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19. Scheme 11: Synthesis of fisetin (67) and quercetin (68). Reagents and conditions: (a) 3,4-dimethoxybenzaldehyd...
  
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20. Figure 8: Structure of (2S)-7,2’,4’-trihydroxy-5-methoxy-8-(dimethylallyl)flavanone (69).
  
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Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

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Studies on the photodegradation of red, green and blue phosphorescent OLED emitters

Susanna Schmidbauer,
Andreas Hohenleutner and
Burkhard König

Full Research Paper
Published 11 Oct 2013

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1. Graphical Abstract
2. Figure 1: Structures of the investigated phosphorescent triscyclometalated iridium complexes.
  
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3. Figure 2: Photodegradation of the different compounds in toluene under ambient atmosphere. Plotted is the rat...
  
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4. Figure 3: Photodegradation behavior of the iridium complexes in CH₂Cl₂ and toluene solution and in a spin-coa...
  
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5. Figure 4: Mass spectra of the identified halogenated degradation products of a) Ir(ppy)₃ after 200 min of irr...
  
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6. Figure 5: Degradation curves of Ir(piq)₃ in benzene and benzene-d₆ under ambient and inert conditions (left)....
  
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7. Figure 6: DAD chromatogram showing the formation of two main degradation products (left) and their assigned m...
  
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8. Figure 7: Degradation curves of Ir(ppy)₃ in benzene and benzene-d₆ under ambient and inert conditions, and ma...
  
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9. Figure 8: (a) Degradation curves of Ir(Me-ppy)₃ in benzene and benzene-d₆ under ambient and inert conditions....
  
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10. Figure 9: Degradation curves of Ir(F,CN-ppy)₃ in benzene, benzene-d₆ and toluene under ambient conditions and...
  
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Beilstein J. Org. Chem. 2013, 9, 2088–2096, doi:10.3762/bjoc.9.245

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New GABA amides activating GABA_A-receptors

Peter Raster,
Andreas Späth,
Svetlana Bultakova,
Pau Gorostiza,
Burkhard König and
Piotr Bregestovski

Full Research Paper
Published 20 Feb 2013

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1. Graphical Abstract
2. Figure 1: The neurotransmitter GABA.
  
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3. Scheme 1: Synthesis of GABA-amide hydrochlorides 4a–c and 6a–f. (i) THF, reflux; (ii) MeOH, HCl (5%); (iii) T...
  
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4. Figure 2: Effect of 7b on GABA_A-receptor activation. (A) Superimposed traces of whole-cell currents induced b...
  
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5. Figure 3: Absence of GABA_A-receptor activation on application of 4c. Top traces: Examples of whole-cell curre...
  
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6. Figure 4: Variation of EC₅₀ values with the number n of methylene units separating the amide and the ammonium...
  
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7. Figure 5: Effect of 7d on GABA_A-receptor activation. (A,B) Superimposed traces of whole-cell currents induced...
  
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Beilstein J. Org. Chem. 2013, 9, 406–410, doi:10.3762/bjoc.9.42

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Parallel solid-phase synthesis of diaryltriazoles

Matthias Wrobel,
Jeffrey Aubé and
Burkhard König

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Published 06 Jul 2012

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1. Graphical Abstract
2. Scheme 1: Terphenyl scaffold 1 [13,14]; oxazole-pyridazine-piperazine 2 [14,15] and aryl-triazoles 3 and 4 [15,16] as α-helix mime...
  
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3. Scheme 2: Synthesis of azido-functionalized resins 7 and 9.
  
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Beilstein J. Org. Chem. 2012, 8, 1027–1036, doi:10.3762/bjoc.8.115

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Reduction of benzylic alcohols and α-hydroxycarbonyl compounds by hydriodic acid in a biphasic reaction medium

Michael Dobmeier,
Josef M. Herrmann,
Dieter Lenoir and
Burkhard König

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Published 02 Mar 2012

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1. Graphical Abstract
2. Scheme 1: Mechanism of the alcohol reduction and recycling of iodine.
  
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Beilstein J. Org. Chem. 2012, 8, 330–336, doi:10.3762/bjoc.8.36

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Molecular recognition of organic ammonium ions in solution using synthetic receptors

Andreas Späth and
Burkhard König

Review
Published 06 Apr 2010

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1. Graphical Abstract
2. Figure 1: Biologically important amines and quaternary ammonium salts: histamine (1), dopamine (2) and acetyl...
  
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3. Figure 2: Crown ether 18-crown-6.
  
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4. Figure 3: Conformations of 18-crown-6 (4) in solvents of different polarity.
  
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5. Figure 4: Binding topologies of the ammonium ion depending on the crown ring size.
  
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6. Figure 5: A “pseudorotaxane” structure consisting of 24-crown-8 and a secondary ammonium ion (5); R = Ph.
  
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7. Figure 6: Typical examples of azacrown ethers, cryptands and related aza macrocycles.
  
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8. Figure 7: Binding of ammonium to azacrown ethers and cryptands [111-113].
  
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9. Figure 8: A 19-crown-6-ether with decalino blocking groups (11) and a thiazole-dibenzo-18-crown-6-ether (12).
  
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10. Figure 9: 1,3-Bis(6-oxopyridazin-1-yl)propane derivatives 13 and 14 by Campayo et al.
  
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11. Figure 10: Fluorescent azacrown-PET-sensors based on coumarin.
  
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12. Figure 11: Two different pyridino-cryptands (17 and 18) compared to a pyridino-crown (19); chiral ammonium ion...
  
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13. Figure 12: Pyridino-18-crown-6 ligand (21), a similar acridino-18-crown-6 ligand (22) and a structurally relat...
  
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14. Figure 13: Ciral pyridine-azacrown ether receptors 24.
  
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15. Figure 14: Chiral 15-crown-5 receptors 26 and an analogue 18-crown-6 ligand 27 derived from amino alcohols.
  
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16. Figure 15: C₂-symmetric chiral 18-crown-6 amino alcohol derivatives 28 and related macrocycles.
  
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17. Figure 16: Macrocycles with diamide-diester groups (30).
  
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18. Figure 17: C₂-symmetric chiral aza-18-crown-6 ethers (31) with phenethylamine residues.
  
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19. Figure 18: Chiral C-pivot p-methoxy-phenoxy-lariat ethers.
  
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20. Figure 19: Chiral lariat crown ether 34.
  
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21. Figure 20: Sucrose-based chiral crown ether receptors 36.
  
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22. Figure 21: Permethylated fructooligosaccharide 37 showing induced-fit chiral recognition.
  
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23. Figure 22: Biphenanthryl-18-crown-6 derivative 38.
  
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24. Figure 23: Chiral lariat crown ethers derived from binol by Fuji et al.
  
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25. Figure 24: Chiral phenolic crown ether 41 with “aryl chiral barriers” and guest amines.
  
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26. Figure 25: Chiral bis-crown receptor 43 with a meso-ternaphthalene backbone.
  
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27. Figure 26: Chromogenic pH-dependent bis-crown chemosensor 44 for diamines.
  
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28. Figure 27: Triamine guests for binding to receptor 44.
  
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29. Figure 28: Chiral bis-crown phenolphthalein chemosensors 46.
  
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30. Figure 29: Crown ether amino acid 47.
  
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31. Figure 30: Luminescent receptor 48 for bis-alkylammonium guests.
  
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32. Figure 31: Luminescent CEAA (49a), a bis-CEAA receptor for amino acids (49b) and the structure of lysine bindi...
  
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33. Figure 32: Luminescent CEAA tripeptide for binding small peptides.
  
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34. Figure 33: Bis crown ether 51a self assembles co-operatively with C₆₀-ammonium ion 51b.
  
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35. Figure 34: Triptycene-based macrotricyclic dibenzo-[24]-crown-8 ether host 52 and guests.
  
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36. Figure 35: Copper imido diacetic acid azacrown receptor 53a and the suggested His-Lys binding motif; a copper ...
  
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37. Figure 36: Urea (54) and thiourea (55) benzo crown receptor for transport and extraction of amino acids.
  
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38. Figure 37: Crown pyryliums ion receptors 56 for amino acids.
  
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39. Figure 38: Ditopic sulfonamide bridged crown ether receptor 57.
  
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40. Figure 39: Luminescent peptide receptor 58.
  
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41. Figure 40: Luminescent receptor 59 for the detection of D-glucosamine hydrochloride in water/ethanol and lumin...
  
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42. Figure 41: Guanidinium azacrown receptor 61 for simple amino acids and ditopic receptor 62 with crown ether an...
  
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43. Figure 42: Chiral bicyclic guanidinium azacrown receptor 63 and similar receptor 64 for the enantioselective t...
  
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44. Figure 43: Receptors for zwitterionic species based on luminescent CEAAs.
  
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45. Figure 44: 1,10-Azacrown ethers with sugar podand arms and the anticancer agent busulfan.
  
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46. Figure 45: Benzo-18-crown-6 modified β-cyclodextrin 69 and β-cyclodextrin functionalized with diaza-18-crown-6...
  
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47. Figure 46: Receptors for colorimetric detection of primary and secondary ammonium ions.
  
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48. Figure 47: Porphyrine-crown-receptors 72.
  
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49. Figure 48: Porphyrin-crown ether conjugate 73 and fullerene-ammonium ion guest 74.
  
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50. Figure 49: Calix[4]arene (75a), homooxocalix[4]arene (75b) and resorcin[4]arene (75c) compared (R = H, alkyl c...
  
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51. Figure 50: Calix[4]arene and ammonium ion guest (R = H, alkyl, OAcyl etc.), possible binding sites; A: co-ordi...
  
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52. Figure 51: Typical guests for studies with calixarenes and related molecules.
  
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53. Figure 52: Lower rim modified p-tert-butylcalix[5]arenes 82.
  
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54. Figure 53: The first example of a water soluble calixarene.
  
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55. Figure 54: Sulfonated water soluble calix[n]arenes that bind ammonium ions.
  
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56. Figure 55: Displacement assay for acetylcholine (3) with a sulfonato-calix[6]arene (84b).
  
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57. Figure 56: Amino acid inclusion in p-sulfonatocalix[4]arene (84a).
  
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58. Figure 57: Calixarene receptor family 86 with upper and lower rim functionalization.
  
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59. Figure 58: Calix[6]arenes 87 with one carboxylic acid functionality.
  
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60. Figure 59: Sulfonated calix[n]arenes with mono-substitution at the lower rim systematically studied on their r...
  
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61. Figure 60: Cyclotetrachromotropylene host (91) and its binding to lysine (81c).
  
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62. Figure 61: Calixarenes 92 and 93 with phosphonic acids groups.
  
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63. Figure 62: Calix[4]arene tetraphosphonic acid (94a) and a double bridged analogue (94b).
  
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64. Figure 63: Calix[4]arene tetraphosphonic acid ester (92c) for surface recognition experiments.
  
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65. Figure 64: Calixarene receptors 95 with α-aminophosphonate groups.
  
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66. Figure 65: A bridged homocalix[3]arene 95 and a distally bridged homocalix[4]crown 96.
  
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67. Figure 66: Homocalix[3]arene ammonium ion receptor 97a and the Reichardt’s dye (97b) for colorimetric assays.
  
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68. Figure 67: Chromogenic diazo-bridged calix[4]arene 98.
  
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69. Figure 68: Calixarene receptor 99 by Huang et al.
  
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70. Figure 69: Calixarenes 100 reported by Parisi et al.
  
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71. Figure 70: Guest molecules for inclusion in calixarenes 100: DAP × 2 HCl (101a), APA (101b) and Lys-OMe × 2 HC...
  
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72. Figure 71: Different N-linked peptido-calixarenes open and with glycol chain bridges.
  
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73. Figure 72: (S)-1,1′-Bi-2-naphthol calixarene derivative 104 published by Kubo et al.
  
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74. Figure 73: A chiral ammonium-ion receptor 105 based on the calix[4]arene skeleton.
  
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75. Figure 74: R-/S-phenylalaninol functionalized calix[6]arenes 106a and 106b.
  
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76. Figure 75: Capped homocalix[3]arene ammonium ion receptor 107.
  
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77. Figure 76: Two C₃ symmetric capped calix[6]arenes 108 and 109.
  
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78. Figure 77: Phosphorous-containing rigidified calix[6]arene 110.
  
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79. Figure 78: Calix[6]azacryptand 111.
  
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80. Figure 79: Further substituted calix[6]azacryptands 112.
  
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81. Figure 80: Resorcin[4]arene (75c) and the cavitands (113).
  
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82. Figure 81: Tetrasulfonatomethylcalix[4]resorcinarene (114).
  
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83. Figure 82: Resorcin[4]arenes (115a/b) and pyrogallo[4]arenes (115c, 116).
  
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84. Figure 83: Displacement assay for acetylcholine (3) with tetracyanoresorcin[4]arene (117).
  
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85. Figure 84: Tetramethoxy resorcinarene mono-crown-5 (118).
  
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86. Figure 85: Components of a resorcinarene based displacement assay for ammonium ions.
  
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87. Figure 86: Chiral basket resorcin[4]arenas 121.
  
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88. Figure 87: Resorcinarenes with deeper cavitand structure (122).
  
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89. Figure 88: Resorcinarene with partially open deeper cavitand structure (123).
  
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90. Figure 89: Water-stabilized deep cavitands with partially structure (124, 125).
  
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91. Figure 90: Charged cavitands 126 for tetralkylammonium ions.
  
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92. Figure 91: Ditopic calix[4]arene receptor 127 capped with glycol chains.
  
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93. Figure 92: A calix[5]arene dimer for diammonium salt recognition.
  
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94. Figure 93: Calixarene parts 92c and 129 for the formation molecular capsules.
  
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95. Figure 94: Encapsulation of a quaternary ammonium cation by two resorcin[4]arene molecules (NMe₄⁺@[75c]₂ × Cl⁻...
  
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96. Figure 95: Encapsulation of a quaternary ammonium cation by six resorcin[4]arene molecules (NMe₃D⁺@[130]₆ × Cl⁻...
  
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97. Figure 96: Structure and schematic of cucurbit[6]uril (CB[6], 131a).
  
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98. Figure 97: Cyclohexanocucurbit[6]uril (CB′[6], 132) and the guest molecule spermine (133).
  
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99. Figure 98: α,α,δ,δ-Tetramethylcucurbit[6]uril (134).
  
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100. Figure 99: Structure of the cucurbituril-phthalhydrazide analogue 135.
  
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101. Figure 100: Organic cavities for the displacement assay for amine differentiation.
  
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102. Figure 101: Displacement assay methodology for diammonium- and related guests involving cucurbiturils and some ...
  
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103. Figure 102: Nor-seco-Cucurbituril (±)-bis-ns-CB[6] (140) and guest molecules.
  
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104. Figure 103: The cucurbit[6]uril based complexes 141 for chiral discrimination.
  
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105. Figure 104: Cucurbit[7]uril (131c) and its ferrocene guests (142) opposed.
  
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106. Figure 105: Cucurbit[7]uril (131c) guest inclusion and representative guests.
  
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107. Figure 106: Cucurbit[7]uril (131c) binding to succinylcholine (145) and different bis-ammonium and bis-phosphon...
  
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108. Figure 107: Paraquat-cucurbit[8]uril complex 149.
  
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109. Figure 108: Gluconuril-based ammonium receptors 150.
  
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110. Figure 109: Examples of clefts (151a), tweezers (151b, 151c, 151d) and clips (151e).
  
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111. Figure 110: Kemp’s triacid (152a), on example of Rebek’s receptors (152b) and guests.
  
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112. Figure 111: Amino acid receptor (154) by Rebek et al.
  
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113. Figure 112: Hexagonal lattice designed hosts by Bell et al.
  
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114. Figure 113: Bell’s amidinium receptor (156) and the amidinium ion (157).
  
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115. Figure 114: Aromatic phosphonic acids.
  
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116. Figure 115: Xylene phosphonates 159 and 160a/b for recognition of amines and amino alcohols.
  
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117. Figure 116: Bisphosphonate recognition motif 161 for a colorimetric assay with alizarin complexone (163) for ca...
  
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118. Figure 117: Bisphosphonate/phosphate clip 164 and bisphosphonate cleft 165.
  
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119. Figure 118: N-Methylpyrazine 166a, N-methylnicotinamide iodide (166b) and NAD⁺ (166c).
  
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120. Figure 119: Bisphosphate cavitands.
  
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121. Figure 120: Bisphosphonate 167 of Schrader and Finocchiaro.
  
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122. Figure 121: Tweezer 168 for noradrenaline (80b).
  
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123. Figure 122: Different tripods and heparin (170).
  
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124. Figure 123: Squaramide based receptors 172.
  
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125. Figure 124: Cage like NH₄⁺ receptor 173 of Kim et al.
  
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126. Figure 125: Ammonium receptors 174 of Chin et al.
  
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127. Figure 126: 2-Oxazolin-based ammonium receptors 175a–d and 176 by Ahn et al.
  
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128. Figure 127: Racemic guest molecules 177.
  
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129. Figure 128: Tripods based on a imidazole containing macrocycle (178) and the guest molecules employed in the st...
  
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130. Figure 129: Ammonium ion receptor 180.
  
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131. Figure 130: Tetraoxa[3.3.3.3]paracyclophanes 181 and a cyclophanic tetraester (182).
  
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132. Figure 131: Peptidic bridged paraquat-cyclophane.
  
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133. Figure 132: Shape-selective noradrenaline host.
  
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134. Figure 133: Receptor 185 for binding of noradrenaline on surface layers from Schrader et al.
  
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135. Figure 134: Tetraphosphonate receptor for binding of noradrenaline.
  
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136. Figure 135: Tetraphosphonate 187 of Schrader and Finocchiaro.
  
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137. Figure 136: Zinc-Porphyrin ammonium-ion receptors 188 and 189 of Mizutani et al.
  
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138. Figure 137: Zinc porphyrin receptor 190.
  
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139. Figure 138: Zinc porphyrin receptors 191 capable of amino acid binding.
  
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140. Figure 139: Zinc-porphyrins with amino acid side chains for stereoinduction.
  
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141. Figure 140: Bis-zinc-bis-porphyrin based on Tröger’s base 193.
  
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142. Figure 141: BINAP-zinc-prophyrin derivative 194 and it’s guests.
  
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143. Figure 142: Bisaryl-linked-zinc-porphyrin receptors.
  
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144. Figure 143: Bis-zinc-porphyrin 199 for diamine recognition and guests.
  
  Jump to Figure 143
145. Figure 144: Bis-zinc-porphyrin crown ether 201.
  
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146. Figure 145: Bis-zinc-porphyrin 202 for stereodiscrimination (L = large substituent; S = small substituent).
  
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147. Figure 146: Bis-zinc-porphyrin[3]rotaxane and its copper complex and guests.
  
  Jump to Figure 146
148. Figure 147: Dien-bipyridyl ligand 206 for co-ordination of two metal atoms.
  
  Jump to Figure 147
149. Figure 148: The ligand and corresponding tetradentate co-complex 207 serving as enantioselective receptor for a...
  
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150. Figure 149: Bis(oxazoline)–copper(II) complex 208 for the recognition of amino acids in aqueous solution.
  
  Jump to Figure 149
151. Figure 150: Zinc-salen-complexes 209 for the recognition tertiary amines.
  
  Jump to Figure 150
152. Figure 151: Bis(oxazoline)–copper(II) 211 for the recognition of amino acids in aqueous solution.
  
  Jump to Figure 151
153. Figure 152: Zn(II)-complex of a C₂ terpyridine crown ether.
  
  Jump to Figure 152
154. Figure 153: Displacement assay and receptor for aspartate over glutamate.
  
  Jump to Figure 153
155. Figure 154: Chiral complex 214 for a colorimetric displacement assay for amino acids.
  
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156. Figure 155: Metal complex receptor 215 with tripeptide side arms.
  
  Jump to Figure 155
157. Figure 156: A sandwich complex 216 and its displaceable dye 217.
  
  Jump to Figure 156
158. Figure 157: Lanthanide complexes 218–220 for amino acid recognition.
  
  Jump to Figure 157
159. Figure 158: Nonactin (221), valinomycin (222) and vancomycin (223).
  
  Jump to Figure 158
160. Figure 159: Monesin (224a) and a chiral analogue for enantiodiscrimination of ammonium guests (224b).
  
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161. Figure 160: Chiral podands (226) compared to pentaglyme-dimethylether (225) and 18-crown-6 (4).
  
  Jump to Figure 160
162. Figure 161: Lasalocid A (228).
  
  Jump to Figure 161
163. Figure 162: Lasalocid derivatives (230) of Sessler et al.
  
  Jump to Figure 162
164. Figure 163: The Coporphyrin I tetraanion (231).
  
  Jump to Figure 163
165. Figure 164: Linear and cyclic peptides for ammonium ion recognition.
  
  Jump to Figure 164
166. Figure 165: Cyclic and bicyclic depsipeptides for ammonium ion recognition.
  
  Jump to Figure 165
167. Figure 166: α-Cyclodextrin (136a) and novocaine (236).
  
  Jump to Figure 166
168. Figure 167: Helical diol receptor 237 by Reetz and Sostmann.
  
  Jump to Figure 167
169. Figure 168: Ammonium binding spherand by Cram et al. (238a) and the cyclic[6]metaphenylacetylene 238b in compar...
  
  Jump to Figure 168
170. Figure 169: Receptor for peptide backbone and ammonium binding (239).
  
  Jump to Figure 169
171. Figure 170: Anion sensor principle with 3-hydroxy-2-naphthanilide of Jiang et al.
  
  Jump to Figure 170
172. Figure 171: 7-bromo-3-hydroxy-N-(2-hydroxyphenyl)naphthalene 2-carboxamide (241) and its amine binding.
  
  Jump to Figure 171
173. Figure 172: Naturally occurring catechins with affinity to quaternary ammonium ions.
  
  Jump to Figure 172
174. Figure 173: Spiropyran (244) and merocyanine form (244a) of the amino acid receptors of Fuji et al.
  
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175. Figure 174: Coumarin aldehyde (245) and its iminium species with amino acid bound (245a) by Glass et al.
  
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176. Figure 175: Coumarin aldehyde appended with boronic acid.
  
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177. Figure 176: Quinolone aldehyde dimers by Glass et al.
  
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178. Figure 177: Chromogenic ammonium ion receptors with trifluoroacetophenone recognition motifs.
  
  Jump to Figure 177
179. Figure 178: Chromogenic ammonium ion receptor with trifluoroacetophenone recognition motif bound on different m...
  
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Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Full Text

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

Harald Schmaderer,
Mouchumi Bhuyan and
Burkhard König

Full Research Paper
Published 28 May 2009

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1. Graphical Abstract
2. Scheme 1: Flavin–guanidinium ion conjugates 1 and 2 and tetraacetyl riboflavin (3).
  
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3. Scheme 2: Synthesis of flavins 1 and 2. Conditions: (i) DMAP, H₂O, Δ, 20 h, 71–78%, (ii) HOBt, EDC, NEt(iPr)₂...
  
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4. Figure 1: X-ray crystal structures of the flavin-Kemp’s acids 6 (left) and 9 (right).
  
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5. Figure 2: Structure of compound 1 in the solid state.
  
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6. Figure 3: Calculated lowest energy conformation of 1 in the gas phase (AM1, Spartan program package).
  
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7. Scheme 3: Oxidative photocleavage of dibenzyl phosphate.
  
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8. Scheme 4: Photoreduction of 4-nitrophenyl phosphate.
  
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9. Scheme 5: Photo Diels–Alder-reaction of anthracene with N-methyl-maleinimide.
  
  Jump to Scheme 5
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Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

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Synthesis of new C^α-tetrasubstituted α-amino acids

Andreas A. Grauer and
Burkhard König

Full Research Paper
Published 18 Feb 2009

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1. Graphical Abstract
2. Figure 1: Proposed reaction mechanism for the formation of C^α-tetrasubstituted tetrahydrofuran α-amino acids.
  
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3. Scheme 1: Cyclisation reaction forming the tetrahydrofuran amino acid (TAA).
  
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4. Figure 2: Structure of compound 15 in the solid state determined by X-ray analysis [21].
  
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Beilstein J. Org. Chem. 2009, 5, No. 5, doi:10.3762/bjoc.5.5

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