Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

Martina Tireli,
Silvija Maračić,
Stipe Lukin,
Marina Juribašić Kulcsár,
Dijana Žilić,
Mario Cetina,
Ivan Halasz,
Silvana Raić-Malić and
Krunoslav Užarević

Full Research Paper
Published 06 Nov 2017

2148 Accesses

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1. Graphical Abstract
2. Scheme 1: Synthetic procedures for preparation of p-halogen-substituted and non-substituted phenyl-1,2,3-tria...
  
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3. Figure 1: Experimental Raman spectra of the alkyne 4 and triazole products 5–8. Bands attributed to the vibra...
  
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4. Figure 2: In situ Raman monitoring of a) mechanochemical formation of triazole 5 using copper(II) acetate mon...
  
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5. Figure 3: a) In situ Raman monitoring for mechanochemical synthesis of 5 using brass balls and PMMA reaction ...
  
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6. Figure 4: ESR spectra of samples obtained after milling by methods 2a (black), 2b (red) and 2c (blue). The in...
  
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7. Figure 5: X-ray structure of the triazole compounds. (a) Molecular structure of 5, with the atom-numbering sc...
  
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Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

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Structure–property relationships and third-order nonlinearities in diketopyrrolopyrrole based D–π–A–π–D molecules

Jan Podlesný,
Lenka Dokládalová,
Oldřich Pytela,
Adam Urbanec,
Milan Klikar,
Numan Almonasy,
Tomáš Mikysek,
Jaroslav Jedryka,
Iwan V. Kityk and
Filip Bureš

Full Research Paper
Published 08 Nov 2017

1897 Accesses

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1. Graphical Abstract
2. Figure 1: General structure of investigated DPP derivatives 1–5.
  
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3. Scheme 1: Synthesis of target DPP chromophores 1–5. (i) PdCl₂(PPh₃)₂, Na₂CO₃, THF, H₂O; (ii) PdCl₂(PPh₃)₂, TH...
  
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4. Figure 2: Thermograms of representative chromophores 4a and 4b.
  
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5. Figure 3: Energy level diagram of the electrochemical (black) and DFT (red) derived energies of the E_HOMO/LUMO...
  
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6. Figure 4: UV–vis absorption spectra of chromophores 1a and 1b in 1,4-dioxane at a concentration of 1 × 10⁻⁵ M....
  
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7. Figure 5: UV–vis absorption spectra of chromophores 1b–5b in 1,4-dioxane at a concentration of 1 × 10⁻⁵ M.
  
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8. Figure 6: Typical THG dependences vs the fundamental energy density.
  
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9. Figure 7: HOMO (red) and LUMO (blue) localizations in 1a (ethylhexyl chains truncated).
  
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Beilstein J. Org. Chem. 2017, 13, 2374–2384, doi:10.3762/bjoc.13.235

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Synthesis of spiro[dihydropyridine-oxindoles] via three-component reaction of arylamine, isatin and cyclopentane-1,3-dione

Yan Sun,
Jing Sun and
Chao-Guo Yan

Full Research Paper
Published 03 Jan 2013

1679 Accesses

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1. Graphical Abstract
2. Scheme 1: The four-component reactions containing dimedone (a) and cyclopentane-1,3-dione (b).
  
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3. Figure 1: Molecular structure of spiro[dihydropyridine-oxindole] 1b.
  
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4. Figure 2: The two kinds of spiro compounds from reactions of isatins with arylamines and cyclic 1,3-diketones....
  
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5. Figure 3: Molecular structure of spiro[dihydropyridine-oxindole] 2f.
  
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6. Scheme 2: Condensation reactions of isatins with cyclopentane-1,3-dione.
  
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7. Figure 4: Molecular structure of compound 3d.
  
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8. Scheme 3: Proposed reaction mechanism for the three-component reaction.
  
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Beilstein J. Org. Chem. 2013, 9, 8–14, doi:10.3762/bjoc.9.2

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An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

Marcus Baumann and
Ian R. Baxendale

Review
Published 30 Oct 2013

1281 Accesses

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1. Graphical Abstract
2. Scheme 1: Scaled industrial processes for the synthesis of simple pyridines.
  
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3. Scheme 2: Synthesis of nicotinic acid from 2-methyl-5-ethylpyridine (1.11).
  
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4. Scheme 3: Synthesis of 3-picoline and nicotinic acid.
  
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5. Scheme 4: Synthesis of 3-picoline from 2-methylglutarodinitrile 1.19.
  
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6. Scheme 5: Picoline-based synthesis of clarinex (no yields reported).
  
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7. Scheme 6: Mode of action of proton-pump inhibitors and structures of the API’s.
  
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8. Scheme 7: Hantzsch-like route towards the pyridine rings in common proton pump inhibitors.
  
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9. Figure 1: Structures of rosiglitazone (1.40) and pioglitazone (1.41).
  
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10. Scheme 8: Synthesis of rosiglitazone.
  
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11. Scheme 9: Syntheses of 2-pyridones.
  
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12. Scheme 10: Synthesis and mechanism of 2-pyrone from malic acid.
  
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13. Scheme 11: Polymer-assisted synthesis of rosiglitazone.
  
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14. Scheme 12: Synthesis of pioglitazone.
  
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15. Scheme 13: Meerwein arylation reaction towards pioglitazone.
  
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16. Scheme 14: Route towards pioglitazone utilising tyrosine.
  
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17. Scheme 15: Route towards pioglitazone via Darzens ester formation.
  
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18. Scheme 16: Syntheses of the thiazolidinedione moiety.
  
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19. Scheme 17: Synthesis of etoricoxib utilising Negishi and Stille cross-coupling reactions.
  
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20. Scheme 18: Synthesis of etoricoxib via vinamidinium condensation.
  
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21. Figure 2: Structures of nalidixic acid, levofloxacin and moxifloxacin.
  
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22. Scheme 19: Synthesis of moxifloxacin.
  
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23. Scheme 20: Synthesis of (S,S)-2,8-diazabicyclo[4.3.0]nonane 1.105.
  
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24. Scheme 21: Synthesis of levofloxacin.
  
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25. Scheme 22: Alternative approach to the levofloxacin core 1.125.
  
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26. Figure 3: Structures of nifedipine, amlodipine and clevidipine.
  
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27. Scheme 23: Mg₃N₂-mediated synthesis of nifedipine.
  
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28. Scheme 24: Synthesis of rac-amlodipine as besylate salt.
  
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29. Scheme 25: Aza Diels–Alder approach towards amlodipine.
  
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30. Scheme 26: Routes towards clevidipine.
  
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31. Figure 4: Examples of piperidine containing drugs.
  
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32. Figure 5: Discovery of tiagabine based on early leads.
  
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33. Scheme 27: Synthetic sequences to tiagabine.
  
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34. Figure 6: Structures of solifenacin (2.57) and muscarine (2.58).
  
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35. Scheme 28: Enantioselective synthesis of solifenacin.
  
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36. Figure 7: Structures of DPP-4 inhibitors of the gliptin-type.
  
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37. Scheme 29: Formation of inactive diketopiperazines from cis-rotameric precursors.
  
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38. Figure 8: Co-crystal structure of carmegliptin bound in the human DPP-4 active site (PDB 3kwf).
  
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39. Scheme 30: Improved route to carmegliptin.
  
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40. Figure 9: Structures of lamivudine and zidovudine.
  
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41. Scheme 31: Typical routes accessing uracil, thymine and cytosine.
  
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42. Scheme 32: Coupling between pyrimidones and riboses via the Vorbrüggen nucleosidation.
  
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43. Scheme 33: Synthesis of lamivudine.
  
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44. Scheme 34: Synthesis of raltegravir.
  
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45. Scheme 35: Mechanistic studies on the formation of 3.22.
  
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46. Figure 10: Structures of selected pyrimidine containing drugs.
  
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47. Scheme 36: General preparation of pyrimidines and dihydropyrimidones.
  
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48. Scheme 37: Synthesis of imatinib.
  
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49. Scheme 38: Flow synthesis of imatinib.
  
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50. Scheme 39: Syntheses of erlotinib.
  
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51. Scheme 40: Synthesis of erlotinib proceeding via Dimroth rearrangement.
  
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52. Scheme 41: Synthesis of lapatinib.
  
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53. Scheme 42: Synthesis of rosuvastatin.
  
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54. Scheme 43: Alternative preparation of the key aldehyde towards rosuvastatin.
  
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55. Figure 11: Structure comparison between nicotinic acetylcholine receptor agonists.
  
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56. Scheme 44: Syntheses of varenicline and its key building block 4.5.
  
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57. Scheme 45: Synthetic access to eszopiclone and brimonidine via quinoxaline intermediates.
  
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58. Figure 12: Bortezomib bound in an active site of the yeast 20S proteasome ([114], pdb 2F16).
  
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59. Scheme 46: Asymmetric synthesis of bortezomib.
  
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60. Figure 13: Structures of some prominent piperazine containing drugs.
  
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61. Figure 14: Structural comparison between the core of aplaviroc (4.35) and a type-1 β-turn (4.36).
  
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62. Scheme 47: Examplary synthesis of an aplaviroc analogue via the Ugi-MCR.
  
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63. Scheme 48: Syntheses of azelastine (5.1).
  
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64. Figure 15: Structures of captopril, enalapril and cilazapril.
  
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65. Scheme 49: Synthesis of cilazapril.
  
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66. Figure 16: Structures of lamotrigine, ceftriaxone and azapropazone.
  
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67. Scheme 50: Synthesis of lamotrigine.
  
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68. Scheme 51: Alternative synthesis of lamotrigine (no yields reported).
  
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69. Figure 17: Structural comparison between imiquimod and the related adenosine nucleoside.
  
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70. Scheme 52: Conventional synthesis of imiquimod (no yields reported).
  
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71. Scheme 53: Synthesis of imiquimod.
  
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72. Scheme 54: Synthesis of imiquimod via tetrazole formation (not all yields reported).
  
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73. Figure 18: Structures of various anti HIV-medications.
  
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74. Scheme 55: Synthesis of abacavir.
  
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75. Figure 19: Structures of diazepam compared to modern replacements.
  
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76. Scheme 56: Synthesis of ocinaplon.
  
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77. Scheme 57: Access to zaleplon and indiplon.
  
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78. Scheme 58: Different routes towards the required N-methylpyrazole 6.65 of sildenafil.
  
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79. Scheme 59: Polymer-supported reagents in the synthesis of key aminopyrazole 6.72.
  
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80. Scheme 60: Early synthetic route to sildenafil.
  
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81. Scheme 61: Convergent preparations of sildenafil.
  
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82. Figure 20: Comparison of the structures of sildenafil, tadalafil and vardenafil.
  
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83. Scheme 62: Short route to imidazotriazinones.
  
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84. Scheme 63: Alternative route towards vardenafils core imidazotriazinone (6.95).
  
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85. Scheme 64: Bayer’s approach to the vardenafil core.
  
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86. Scheme 65: Large scale synthesis of vardenafil.
  
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87. Scheme 66: Mode of action of temozolomide (6.105) as methylating agent.
  
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88. Scheme 67: Different routes to temozolomide.
  
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89. Scheme 68: Safer route towards temozolomide.
  
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90. Figure 21: Some unreported heterocyclic scaffolds in top market drugs.
  
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Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

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High-yielding continuous-flow synthesis of antimalarial drug hydroxychloroquine

Eric Yu,
Hari P. R. Mangunuru,
Nakul S. Telang,
Caleb J. Kong,
Jenson Verghese,
Stanley E. Gilliland III,
Saeed Ahmad,
Raymond N. Dominey and
B. Frank Gupton

Full Research Paper
Published 08 Mar 2018

1224 Accesses

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1. Graphical Abstract
2. Figure 1: Commercially available antimalarial drugs.
  
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3. Scheme 1: Current batch syntheses of the key intermediate 5-(ethyl(2-hydroxyethyl)amino)pentan-2-one (6).
  
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4. Scheme 2: Retrosynthetic strategy to hydroxychloroquine (1).
  
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5. Scheme 3: Schematic representation for continuous in-line extraction of 10.
  
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6. Scheme 4: Optimization of the flow process for the synthesis of 12.
  
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Beilstein J. Org. Chem. 2018, 14, 583–592, doi:10.3762/bjoc.14.45

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Correction: Mechanochemical enzymatic resolution of N-benzylated-β³-amino esters

Mario Pérez-Venegas,
Gloria Reyes-Rangel,
Adrián Neri,
Jaime Escalante and
Eusebio Juaristi

Correction
Published 12 Oct 2017

961 Accesses

Beilstein J. Org. Chem. 2017, 13, 2128–2130, doi:10.3762/bjoc.13.210

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Disposable cartridge concept for the on-demand synthesis of turbo Grignards, Knochel–Hauser amides, and magnesium alkoxides

Mateo Berton,
Kevin Sheehan,
Andrea Adamo and
D. Tyler McQuade

Full Research Paper
Published 19 Jun 2020

784 Accesses

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1. Graphical Abstract
2. Figure 1: Comparing on-demand coffee and turbo Grignard pod-style machines.
  
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3. Figure 2: Ranking of the 20 most cited Grignard reagents (SciFinder March 26, 2019).
  
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4. Figure 3: On-demand prototype. A) Inside view of the pump with a flexible bag containing a yellow liquid layi...
  
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5. Figure 4: Temperature evolution measured with thermocouples along the column outer surface at three different...
  
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6. Figure 5: Stratified bicomponent column (Diba Omnifit EZ Solvent Plus) composed of magnesium (chips/powder, 1...
  
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7. Scheme 1: Continuous flow synthesis of TMPMgCl⋅LiCl with a stratified packed-bed column of activated magnesiu...
  
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8. Scheme 2: Continuous flow synthesis of TMPMgCl⋅LiBr with a stratified packed-bed column of activated magnesiu...
  
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9. Scheme 3: Continuous flow synthesis of t-AmylOMgCl⋅LiCl with a stratified packed-bed column of activated magn...
  
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10. Figure 6: Steady-state concentration stability during the conversion of iPrCl in THF (56 mL, 2.2 M) into iPrM...
  
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11. Scheme 4: Synthesis of iPrMgCl⋅LiCl on the ODR prototype.
  
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12. Scheme 5: Synthesis of HMDSMgCl⋅LiCl on the ODR prototype.
  
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Beilstein J. Org. Chem. 2020, 16, 1343–1356, doi:10.3762/bjoc.16.115

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Heterogeneous photocatalysis in flow chemical reactors

Christopher G. Thomson,
Ai-Lan Lee and
Filipe Vilela

Review
Published 26 Jun 2020

698 Accesses

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1. Graphical Abstract
2. Figure 1: A) Bar chart of the publications per year for the topics “Photocatalysis” (49,662 instances) and “P...
  
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3. Figure 2: A) Professor Giacomo Ciamician and Dr. Paolo Silber on their roof laboratory at the University of B...
  
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4. Scheme 1: PRC trifluoromethylation of N-methylpyrrole (1) using hazardous gaseous CF₃I safely in a flow react...
  
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5. Figure 3: A) Unit cells of the three most common crystal structures of TiO₂: rutile, brookite, and anatase. R...
  
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6. Figure 4: Illustration of the key semiconductor photocatalysis events: 1) A photon with a frequency exceeding...
  
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7. Figure 5: Photocatalytic splitting of water by oxygen vacancies on a TiO₂(110) surface. Reprinted with permis...
  
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8. Figure 6: Proposed adsorption modes of A) benzene, B) chlorobenzene, C) toluene, D) phenol, E) anisole, and F...
  
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9. Figure 7: Structures of the sulfonate-containing organic dyes RB5 (3) and MX-5B (4) and the adsorption isothe...
  
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10. Figure 8: Idealised triclinic unit cell of a g-C₃N₄ type polymer, displaying possible hopping transport scena...
  
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11. Figure 9: Idealised structure of a perfect g-C₃N₄ sheet. The central unit highlighted in red represents one t...
  
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12. Figure 10: Timeline of the key processes of charge transport following the photoexcitation of g-C₃N₄, leading ...
  
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13. Scheme 2: Photocatalytic bifunctionalisation of heteroarenes using mpg-C₃N₄, with the selected examples 5 and ...
  
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14. Figure 11: A) Structure of four linear conjugated polymer photocatalysts for hydrogen evolution, displaying th...
  
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15. Figure 12: Graphical representation of the common methods used to immobilise molecular photocatalysts (PC) ont...
  
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16. Figure 13: Wireless light emitter-supported TiO₂ (TiO₂@WLE) HPCat spheres powered by resonant inductive coupli...
  
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17. Figure 14: Graphical representation of zinc–perylene diimide (Zn-PDI) supramolecular assembly photocatalysis v...
  
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18. Scheme 3: Upconversion of NIR photons to the UV frequency by NaYF₄:Yb,Tm nanocrystals sequentially coated wit...
  
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19. Figure 15: Types of reactors employed in heterogeneous photocatalysis in flow. A) Fixed bed reactors and the s...
  
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20. Figure 16: Electrochemical potential of common semiconductor, transition metal, and organic dye-based photocat...
  
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21. Scheme 4: Possible mechanisms of an immobilised molecular photoredox catalyst by oxidative or reductive quenc...
  
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22. Scheme 5: Scheme of the CMB-C₃N₄ photocatalytic decarboxylative fluorination of aryloxyacetic acids, with the...
  
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23. Scheme 6: Scheme of the g-C₃N₄ photocatalytic desilylative coupling reaction in flow and proposed mechanism [208].
  
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24. Scheme 7: Proposed mechanism of the radical cyclisation of unsaturated alkyl 2-bromo-1,3-dicarbonyl compounds...
  
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25. Scheme 8: N-alkylation of benzylamine and schematic of the TiO₂-coated microfluidic device [213].
  
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26. Scheme 9: Proposed mechanism of the Pt@TiO₂ photocatalytic deaminitive cyclisation of ʟ-lysine (23) to ʟ-pipe...
  
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27. Scheme 10: A) Proposed mechanism for the photocatalytic oxidation of phenylboronic acid (24). B) Photos and SE...
  
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28. Scheme 11: Proposed mechanism for the DA-CMP3 photocatalytic aza-Henry reaction performed in a continuous flow...
  
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29. Scheme 12: Proposed mechanism for the formation of the cyclic product 32 by TiO₂-NC HPCats in a slurry flow re...
  
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30. Scheme 13: Reaction scheme for the photocatalytic synthesis of homo and hetero disulfides in flow and scope of...
  
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31. Scheme 14: Reaction scheme for the MoO_x/TiO₂ HPCat oxidation of cyclohexane (34) to benzene. The graph shows t...
  
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32. Scheme 15: Proposed mechanism of the TiO₂ HPC heteroarene C–H functionalisation via aryl radicals generated fr...
  
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33. Scheme 16: Scheme of the oxidative coupling of benzylamines with the HOTT-HATN HPCat and selected examples of ...
  
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34. Scheme 17: Photocatalysis oxidation of benzyl alcohol (40) to benzaldehyde (41) in a microflow reactor coated ...
  
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35. Figure 17: Mechanisms of Dexter and Forster energy transfer.
  
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36. Scheme 18: Continuous flow process for the isomerisation of alkenes with an ionic liquid-immobilised photocata...
  
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37. Scheme 19: Singlet oxygen synthetic step in the total synthesis of canataxpropellane [265].
  
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38. Scheme 20: Scheme and proposed mechanism of the singlet oxygen photosensitisation by CMP_X HPCats, with the st...
  
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39. Scheme 21: Structures of CMP HPCat materials applied by Vilela and co-workers for the singlet oxygen photosens...
  
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40. Scheme 22: Polyvinylchloride resin-supported TDCPP photosensitisers applied for singlet oxygen photosensitisat...
  
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41. Scheme 23: Structure of the ionically immobilised TPP photosensitiser on amberlyst-15 ion exchange resins (TPP...
  
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42. Scheme 24: Photosensitised singlet oxygen oxidation of citronellol (46) in scCO₂, with automatic phase separat...
  
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43. Scheme 25: Schematic of PS-Est-BDP-Cl₂ being applied for singlet oxygen photosensitisation in flow. A) Pseudo-...
  
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44. Scheme 26: Reaction scheme of the singlet oxygen oxidation of furoic acid (54) using a 3D-printed microfluidic...
  
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45. Figure 18: A) Photocatalytic bactericidal mechanism by ROS oxidative cleavage of membrane lipids (R = H, amino...
  
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46. Figure 19: A) Suggested mechanisms for the aqueous pollutant degradation by TiO₂ in a slurry flow reactor [284-287]. B)...
  
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47. Figure 20: Schematic of the flow system used for the degradation of aqueous oxytetracycline (56) solutions [215]. M...
  
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48. Scheme 27: Degradation of a salicylic acid (57) solution by a coupled solar photoelectro-Fenton (SPEF) process...
  
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49. Figure 21: A) Schematic flow diagram using the TiO₂-coated NETmix microfluidic device for an efficient mass tr...
  
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Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

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Photocatalytic trifluoromethoxylation of arenes and heteroarenes in continuous-flow

Alexander V. Nyuchev,
Ting Wan,
Borja Cendón,
Carlo Sambiagio,
Job J. C. Struijs,
Michelle Ho,
Moisés Gulías,
Ying Wang and
Timothy Noël

Full Research Paper
Published 15 Jun 2020

669 Accesses

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1. Graphical Abstract
2. Scheme 1: A) Properties and B) synthesis of CF₃O-bearing arenes; C) trifluoromethoxylation using the “second”...
  
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3. Scheme 2: Optimization of residence time. ¹⁹F NMR yields are reported.
  
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4. Scheme 3: Scope of photoredox trifluoromethoxylation in continuous-flow. In case of different products, the m...
  
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5. Figure 1: Effect of KH₂PO₄ – other substrates. ^a Conditions as for entry 15 (Table 2), 1 h residence time; ^b conditi...
  
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Beilstein J. Org. Chem. 2020, 16, 1305–1312, doi:10.3762/bjoc.16.111

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Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

Carlos H. Escalante,
Eder I. Martínez-Mora,
Carlos Espinoza-Hicks,
Alejandro A. Camacho-Dávila,
Fernando R. Ramos-Morales,
Francisco Delgado and
Joaquín Tamariz

Full Research Paper
Published 17 Jun 2020

627 Accesses

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1. Graphical Abstract
2. Figure 1: Fused aza-hetero polycyclic frames and natural pyrrolizine- and isoindole-containing alkaloids.
  
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3. Scheme 1: Synthetic approaches for the preparation of pyrrolo-fused aza-hetero polycyclic frames.
  
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4. Scheme 2: Preparation of 1,2-substituted pyrroles 8a–f and 8i,j.
  
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5. Scheme 3: Diels–Alder cycloadditions of pyrroles 8a–j and 16a–b with maleimides 7b–c.
  
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6. Figure 2: Structures of 9m (a) and 10m (b) as determined by single-crystal X-ray diffraction crystallography ...
  
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7. Scheme 4: Pd(0)-catalyzed intramolecular Heck cross-coupling reaction of 2-vinylpyrroles 8c,d and 8g.
  
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8. Scheme 5: Synthesis of 2-vinylpyrroles 8k,l and their Pd(0)-catalyzed intramolecular Heck cross-coupling to p...
  
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9. Scheme 6: Diastereoselective Diels–Alder reaction of pyrrolo[2,1-a]isoindole 18a with 7c.
  
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10. Scheme 7: Synthetic approach to the fused aza-heterocyclic pentacycle 12.
  
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11. Figure 3: M06-2X/6-31+G(d,p) Optimized geometry for each of the SCs (a and d), TSs (b and e) and ADs (c and f...
  
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12. Figure 4: M06-2X/6-31+G(d,p) Optimized geometry for each of the TSs of the Diels–Alder reactions of dienes 8b...
  
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13. Figure 5: M06-2X/6-31+G(d,p) Optimized geometry of the endo SCs (a) and TSs (b) for the Diels–Alder reaction ...
  
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Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

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