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

1812 Accesses

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Album
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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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

1626 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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The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

Marcus Baumann and
Ian R. Baxendale

Review
Published 17 Jul 2015

852 Accesses

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Album
1. Graphical Abstract
2. Figure 1: Pharmaceutical structures targeted in early flow syntheses.
  
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3. Scheme 1: Flow synthesis of 6-hydroxybuspirone (9). Inserted photograph reprinted with permission from [45]. Copy...
  
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4. Figure 2: Configuration of a baffled reactor tube (left) and its schematic working principle (right).
  
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5. Scheme 2: McQuade’s flow synthesis of ibuprofen (16).
  
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6. Scheme 3: Jamison’s flow synthesis of ibuprofen sodium salt (17).
  
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7. Scheme 4: Flow synthesis of imatinib (23).
  
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8. Scheme 5: Flow synthesis of the potent 5HT1B antagonist 28.
  
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9. Scheme 6: Flow synthesis of a selective δ-opioid receptor agonist 33.
  
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10. Scheme 7: Flow synthesis of a casein kinase I inhibitor library (38).
  
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11. Scheme 8: Flow synthesis of fluoxetine (46).
  
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12. Scheme 9: Flow synthesis of artemisinin (55).
  
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13. Scheme 10: Telescoped flow synthesis of artemisinin (55) and derivatives (62–64).
  
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14. Scheme 11: Flow approach towards AZD6906 (65).
  
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15. Scheme 12: Pilot scale flow synthesis of key intermediate 73.
  
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16. Scheme 13: Semi-flow synthesis of vildagliptine (77).
  
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17. Scheme 14: Pilot scale asymmetric flow hydrogenation towards 83. Inserted photograph reprinted with permission...
  
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18. Figure 3: Schematic representation of the ‘tube-in-tube’ reactor.
  
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19. Scheme 15: Flow synthesis of fanetizole (87) via tube-in-tube system.
  
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20. Scheme 16: Flow synthesis of diphenhydramine^.HCl (92).
  
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21. Scheme 17: Flow synthesis of rufinamide (95).
  
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22. Scheme 18: Large scale flow synthesis of rufinamide precursor 102.
  
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23. Scheme 19: First stage in the flow synthesis of meclinertant (103).
  
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24. Scheme 20: Completion of the flow synthesis of meclinertant (103).
  
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25. Scheme 21: Flow synthesis of olanzapine (121) utilising inductive heating techniques.
  
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26. Scheme 22: Flow synthesis of amitriptyline·HCl (127).
  
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27. Scheme 23: Flow synthesis of E/Z-tamoxifen (132) using peristaltic pumping modules.
  
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28. Figure 4: Container sized portable mini factory (photograph credit: INVITE GmbH, Leverkusen Germany).
  
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29. Scheme 24: Flow synthesis of imidazo[1,2-a]pyridines 136 linked to frontal affinity chromatography (FAC).
  
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30. Figure 5: Structures of zolpidem (142) and alpidem (143).
  
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31. Scheme 25: Synthesis and screening loops in the discovery of new Abl kinase inhibitors.
  
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32. Figure 6: Schotten–Baumann approach towards LY573636^.Na (147).
  
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33. Scheme 26: Pilot scale flow synthesis of LY2886721 (146).
  
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34. Scheme 27: Continuous flow manufacture of alikiren hemifumarate 152.
  
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Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134

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A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes

Constantin Stuckhardt,
Diederik Roke,
Wojciech Danowski,
Edwin Otten,
Sander J. Wezenberg and
Ben L. Feringa

Full Research Paper
Published 15 Nov 2019

729 Accesses

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1. Graphical Abstract
2. Figure 1: Schematic representation of a photoresponsive cage with ligands based on overcrowded alkenes.
  
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3. Scheme 1: Cage formation of overcrowded alkene switches E/Z-1 and their isomerization behavior. Note that the...
  
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4. Figure 2: Aromatic region of stacked ¹H NMR spectra (in CD₃CN) of stable Z-1 and cage complex Pd₂(stable Z-1)₄...
  
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5. Figure 3: HRMS spectra of cage complex Pd₂(stable Z-1)₄ (top) and cage complex Pd₂(stable E-1)₄ (bottom); Ins...
  
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6. Figure 4: Crystal structure of cage complex Pd₂(stable E-1)₄ (top left) and DFT optimized structures of cage ...
  
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7. Figure 5: Aromatic region of stacked ¹H NMR spectra (CD₃CN/CD₂Cl₂ 1:1) of i) Pd₂(stable Z-1)₄; ii) Pd₂(stable ...
  
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Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268

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An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

Marcus Baumann,
Ian R. Baxendale,
Steven V. Ley and
Nikzad Nikbin

Review
Published 18 Apr 2011

700 Accesses

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Album
1. Graphical Abstract
2. Figure 1: Structures of atorvastatin and other commercial statins.
  
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3. Figure 2: Structure of compactin.
  
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4. Scheme 1: Synthesis of pentasubstituted pyrroles.
  
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5. Scheme 2: [3 + 2] Cycloaddition to prepare 5-isopropylpyrroles.
  
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6. Scheme 3: Regiospecific [3 + 2] cycloaddition to prepare the pyrrole scaffold.
  
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7. Scheme 4: Formation of the pyrrole core of atorvastatin via [3 + 2] cycloaddition.
  
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8. Scheme 5: Formation of pyrrole 33 via the Paal–Knorr reaction.
  
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9. Scheme 6: Convergent synthesis towards atorvastatin.
  
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10. Figure 3: Binding pocket of sunitinib in the TRK KIT.
  
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11. Scheme 7: Synthesis of sunitinib.
  
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12. Scheme 8: Alternative synthesis of sunitinib.
  
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13. Scheme 9: Key steps in the syntheses of sumatriptan and zolmitriptan.
  
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14. Scheme 10: Introduction of the N,N-dimethylaminoethyl side chain.
  
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15. Scheme 11: Japp–Klingemann reaction in the synthesis of sumatriptan.
  
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16. Scheme 12: Synthesis of the intermediate sulfonyl chlorides 62 and 63.
  
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17. Scheme 13: Alternative introduction of the sulfonamide.
  
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18. Scheme 14: Negishi-type coupling to benzylic sulfonamides.
  
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19. Scheme 15: Heck reaction used to introduce the sulfonamide side chain of naratriptan.
  
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20. Scheme 16: Synthesis of the oxazolinone appendage of zolmitriptan.
  
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21. Scheme 17: Grandberg indole synthesis used in the preparation of rizatriptan.
  
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22. Scheme 18: Improved synthesis of rizatriptan.
  
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23. Scheme 19: Larock-type synthesis of rizatriptan.
  
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24. Scheme 20: Synthesis of eletriptan.
  
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25. Scheme 21: Heck coupling for the indole system in eletriptan.
  
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26. Scheme 22: Attempted Fischer indole synthesis of elatriptan.
  
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27. Scheme 23: Successful Fischer indole synthesis for eletriptan.
  
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28. Scheme 24: Mechanistic rationale for the Bischler–Möhlau reaction.
  
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29. Scheme 25: Bischler-type indole synthesis used in the fluvastatin sodium synthesis.
  
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30. Scheme 26: Palladium-mediated synthesis of ondansetron.
  
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31. Scheme 27: Fischer indole synthesis of ondansetron.
  
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32. Scheme 28: Optimised Pictet–Spengler reaction towards tadalafil.
  
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33. Figure 4: Structures of carvedilol 136 and propranolol 137.
  
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34. Scheme 29: Synthesis of the carbazole core of carvedilol.
  
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35. Scheme 30: Alternative syntheses of 4-hydroxy-9H-carbazole.
  
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36. Scheme 31: Convergent synthesis of etodolac.
  
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37. Scheme 32: Alternative synthesis of etodolac.
  
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38. Figure 5: Structures of imidazole-containing drugs.
  
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39. Scheme 33: Synthesis of functionalised imidazoles towards losartan.
  
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40. Scheme 34: Direct synthesis of the chlorinated imidazole in losartan.
  
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41. Scheme 35: Synthesis of trisubstituted imidazoles.
  
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42. Scheme 36: Preparation of the imidazole ring in olmesartan.
  
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43. Scheme 37: Synthesis of ondansetron.
  
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44. Scheme 38: Alternative route to ondansetron and its analogues.
  
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45. Scheme 39: Proton pump inhibitors and synthesis of esomeprazole.
  
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46. Scheme 40: Synthesis of benzimidazole core pantoprazole.
  
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47. Figure 6: Structure of rabeprazole 194.
  
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48. Scheme 41: Synthesis of candesartan.
  
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49. Scheme 42: Alternative access to the candesartan key intermediate 216.
  
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50. Scheme 43: .Medicinal chemistry route to telmisartan.
  
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51. Scheme 44: Improved synthesis of telmisartan.
  
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52. Scheme 45: Synthesis of zolpidem.
  
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53. Scheme 46: Copper-catalysed 3-component coupling towards zolpidem.
  
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54. Figure 7: Structure of celecoxib.
  
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55. Scheme 47: Preparation of celecoxib.
  
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56. Scheme 48: Alternative synthesis of celecoxib.
  
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57. Scheme 49: Regioselective access to celecoxib.
  
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58. Scheme 50: Synthesis of pazopanib.
  
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59. Scheme 51: Syntheses of anastrozole, rizatriptan and letrozole.
  
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60. Scheme 52: Regioselective synthesis of anastrozole.
  
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61. Scheme 53: Triazine-mediated triazole formation towards anastrozole.
  
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62. Scheme 54: Alternative routes to 1,2,4-triazoles.
  
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63. Scheme 55: Initial synthetic route to sitagliptin.
  
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64. Figure 8: Binding of sitagliptin within DPP-IV.
  
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65. Scheme 56: The process route to sitagliptin key intermediate 280.
  
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66. Scheme 57: Synthesis of maraviroc.
  
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67. Scheme 58: Synthesis of alprazolam.
  
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68. Scheme 59: The use of N-nitrosoamidine derivatives in the preparation of fused benzodiazepines.
  
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69. Figure 9: Structures of itraconazole, ravuconazole and voriconazole.
  
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70. Scheme 60: Synthesis of itraconazole.
  
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71. Scheme 61: Synthesis of rufinamide.
  
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72. Scheme 62: Representative tetrazole formation in valsartan.
  
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73. Figure 10: Structure of tetrazole containing olmesartan, candesartan and irbesartan.
  
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74. Scheme 63: Early stage introduction of the tetrazole in losartan.
  
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75. Scheme 64: Synthesis of cilostazol.
  
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76. Figure 11: Structure of cefdinir.
  
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77. Scheme 65: Semi-synthesis of cefdinir.
  
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78. Scheme 66: Thiazole syntheses towards ritonavir.
  
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79. Scheme 67: Synthesis towards pramipexole.
  
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80. Scheme 68: Alternative route to pramipexole.
  
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81. Scheme 69: Synthesis of famotidine.
  
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82. Scheme 70: Efficient synthesis of the hyperuricemic febuxostat.
  
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83. Scheme 71: Synthesis of ziprasidone.
  
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84. Figure 12: Structure of mometasone.
  
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85. Scheme 72: Industrial access to 2-furoic acid present in mometasone.
  
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86. Scheme 73: Synthesis of ranitidine from furfuryl alcohol.
  
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87. Scheme 74: Synthesis of nitrofurantoin.
  
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88. Scheme 75: Synthesis of benzofuran.
  
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89. Scheme 76: Synthesis of amiodarone.
  
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90. Scheme 77: Synthesis of raloxifene.
  
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91. Scheme 78: Alternative access to the benzo[b]thiophene core of raloxifene.
  
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92. Scheme 79: Gewald reaction in the synthesis of olanzapine.
  
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93. Scheme 80: Alternative synthesis of olanzapine.
  
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94. Figure 13: Access to simple thiophene-containing drugs.
  
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95. Scheme 81: Synthesis of clopidogrel.
  
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96. Scheme 82: Pictet–Spengler reaction in the preparation of tetrahydrothieno[3,2-c]pyridine (422).
  
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97. Scheme 83: Alternative synthesis of key intermediate 422.
  
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98. Figure 14: Co-crystal structures of timolol (left) and carazolol (right) in the β-adrenergic receptor.
  
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99. Scheme 84: Synthesis of timolol.
  
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100. Scheme 85: Synthesis of tizanidine 440.
  
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101. Scheme 86: Synthesis of leflunomide.
  
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102. Scheme 87: Synthesis of sulfamethoxazole.
  
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103. Scheme 88: Synthesis of risperidone.
  
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104. Figure 15: Relative abundance of selected transformations.
  
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105. Figure 16: The abundance of heterocycles within top 200 drugs (5-membered rings).
  
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Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

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A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

Magnus Rueping and
Boris J. Nachtsheim

Review
Published 20 Jan 2010

690 Accesses

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Album
1. Graphical Abstract
2. Scheme 1: AlCl₃-mediated reaction between amyl chloride and benzene as developed by Friedel and Crafts.
  
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3. Figure 1: Most often used metal salts for catalytic FC alkylations and hydroarylations of arenes.
  
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4. Figure 2: 1,1-diarylalkanes with biological activity.
  
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5. Scheme 2: Alkylating reagents and side products produced.
  
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6. Scheme 3: Initially reported TeCl₄-mediated FC alkylation of 1-penylethanol with toluene.
  
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7. Scheme 4: Sc(OTf)₃-catalyzed FC benzylation of arenes.
  
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8. Scheme 5: Reductive FC alkylation of arenes with arenecarbaldehydes.
  
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9. Scheme 6: Iron(III)-catalyzed FC benzylation of arenes and heteroarenes.
  
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10. Scheme 7: A gold(III)-catalyzed route to beclobrate.
  
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11. Scheme 8: Catalytic FC-type alkylations of 1,3-dicarbonyl compounds.
  
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12. Scheme 9: Iron(III)-catalyzed synthesis of phenprocoumon.
  
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13. Scheme 10: Bi(OTf)₃-catalyzed FC alkylation of benzyl alcohols developed by Rueping et al.
  
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14. Scheme 11: (A) Bi(OTf)₃-catalyzed intramolecular FC alkylation as an efficient route to substituted fulvenes. ...
  
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15. Scheme 12: FC-type glycosylation of 1,2-dimethylindole and trimethoxybenzene.
  
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16. Scheme 13: FC alkylation with highly reactive ferrocenyl- and benzyl alcohols. The reaction proceeds even with...
  
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17. Scheme 14: Reductive FC alkylation of arenes with benzaldehyde and acetophenone catalyzed by the Ir-carbene co...
  
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18. Scheme 15: Formal synthesis of 1,1-diarylalkanes from benzyl alcohols and styrenes.
  
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19. Scheme 16: (A) Mo-catalyzed hydroarylation of styrenes and cyclohexenes. (B) Hydroalkylation–cyclization casca...
  
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20. Scheme 17: Bi(III)-catalyzed hydroarylation of styrenes with arenes and heteroarenes.
  
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21. Scheme 18: BiCl₃-catalyzed ene/FC alkylation reaction cascade – A fast access to highly arylated dihydroindene...
  
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22. Scheme 19: Au(I)/Ag(I)-catalyzed hydroarylation of indoles with styrenes, aliphatic and cyclic alkenes.
  
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23. Scheme 20: First transition-metal-catalyzed ortho-hydroarylation developed by Beller et al.
  
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24. Scheme 21: (A) Ti(IV)-mediated rearrangement of an N-benzylated aniline to the corresponding ortho-alkylated a...
  
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25. Scheme 22: Dibenzylation of aniline gives potentially useful amine-based ligands in a one-step procedure.
  
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26. Scheme 23: FC-type alkylations with allyl alcohols as alkylating reagents – linear vs. branched product format...
  
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27. Scheme 24: (A) First catalytic FC allylation and cinnamylation using allyl alcohols and its derivatives. (B) E...
  
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28. Scheme 25: FC allylation/cyclization reaction yielding substituted chromanes.
  
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29. Scheme 26: Synthesis of (all-rac)-α-tocopherol utilizing Lewis- and strong Brønsted-acids.
  
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30. Scheme 27: Au(III)-catalyzed cinnamylation of arenes.
  
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31. Scheme 28: “Exhaustive” allylation of benzene-1,3,5-triol.
  
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32. Scheme 29: Palladium-catalyzed allylation of indole.
  
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33. Scheme 30: Pd-catalyzed synthesis of pyrroloindoles from L-tryptophane.
  
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34. Scheme 31: Ru(IV)-catalyzed allylation of indole and pyrroles with unique regioselectivity.
  
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35. Scheme 32: Silver(I)-catalyzed intramolecular FC-type allylation of arenes and heteroarenes.
  
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36. Scheme 33: FC-type alkylations of arenes using propargyl alcohols.
  
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37. Scheme 34: (A) Propargylation of arenes with stoichiometric amounts of the Ru-allenylidene complex 86. (B) Fir...
  
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38. Scheme 35: Diruthenium-catalyzed formation of chromenes and 1H-naphtho[2,1-b]pyrans.
  
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39. Scheme 36: Rhenium(V)-catalyzed FC propargylations as a first step in the total synthesis of podophyllotoxin, ...
  
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40. Scheme 37: Scandium-catalyzed arylation of 3-sulfanyl- and 3-selanylpropargyl alcohols.
  
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41. Scheme 38: Synthesis of 1,3-diarylpropynes via direct coupling of propargyl trichloracetimidates and arenes.
  
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42. Scheme 39: Diastereoselective substitutions of benzyl alcohols.
  
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43. Scheme 40: (A) First diastereoselective FC alkylations developed by Bach et al. (B) anti-Selective FC alkylati...
  
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44. Scheme 41: Diastereoselective AuCl₃-catalyzed FC alkylation.
  
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45. Scheme 42: Bi(OTf)₃-catalyzed alkylation of α-chiral benzyl acetates with silyl enol ethers.
  
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46. Scheme 43: Bi(OTf)₃-catalyzed diastereoselective substitution of propargyl acetates.
  
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47. Scheme 44: Nucelophilic substitution of enantioenriched ferrocenyl alcohols.
  
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48. Scheme 45: First catalytic enantioselective propargylation of arenes.
  
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Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

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Computational methods in drug discovery

Sumudu P. Leelananda and
Steffen Lindert

Review
Published 12 Dec 2016

666 Accesses

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1. Graphical Abstract
2. Figure 1: Schematic representation of a computer-aided drug discovery (CADD) pipeline. CADD methods are broad...
  
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3. Figure 2: FDA approved drugs Saquinavir and Amprenavir for the treatment of HIV infections. (a) The structure...
  
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4. Figure 3: (a) The crystal structure showing the binding of Dorzolamide (orange) to carbonic anhydrase II (pur...
  
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5. Figure 4: The best ligand binding site identified by SiteHound in HIV-1 protease. The ligand binding pocket i...
  
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6. Figure 5: Binding mode prediction. The known inhibitor Dorzolamide is docked into Carbonic anhydrase II cryst...
  
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7. Figure 6: The molecular structure of Raltegravir. Raltegravir is an FDA approved drug used in the treatment o...
  
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8. Figure 7: An example alchemical thermodynamic cycle for a protein–ligand binding free energy calculation. The...
  
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9. Figure 8: Schematic diagram showing the steps involved in QSAR. Known drug molecule activity and descriptor d...
  
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10. Figure 9: A few drugs discovered with the help of ligand-based drug discovery tools. (a) Zolmitriptan: used a...
  
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Beilstein J. Org. Chem. 2016, 12, 2694–2718, doi:10.3762/bjoc.12.267

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Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

Eric J. N. Helfrich,
Geng-Min Lin,
Christopher A. Voigt and
Jon Clardy

Review
Published 29 Nov 2019

618 Accesses

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1. Graphical Abstract
2. Figure 1: Examples of bioactive terpenoids.
  
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3. Figure 2: Repetitive electrophilic and nucleophilic functionalities in terpene and type II PKS-derived polyke...
  
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4. Figure 3: Abundance and distribution of bacterial terpene biosynthetic gene clusters as determined by genome ...
  
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5. Figure 4: Terpenoid biosynthesis. Terpenoid biosynthesis is divided into two phases, 1) terpene scaffold gene...
  
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6. Figure 5: Mechanisms for type I, type II, and type II/type I tandem terpene cyclases. a) Tail-to-head class I...
  
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7. Figure 6: Functional TC characterization. a) Different terpenes were produced when hedycaryol (18) synthase a...
  
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8. Figure 7: Selected examples of terpene modification by bacterial CYPs. a) Hydroxylation [89]. b) Carboxylation, h...
  
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9. Figure 8: Off-target effects observed during heterologous expression of terpenoid BGCs. Unexpected oxidation ...
  
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10. Figure 9: TC promiscuity and engineering. a) Spata-13,17-diene (39) synthase (SpS) can take C₁₅ and C₂₅ oligo...
  
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11. Figure 10: Substrate promiscuity and engineering of CYPs. a) Selected examples from using a CYP library to oxi...
  
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12. Figure 11: Engineering of terpenoid pathways. a) Metabolic network of terpenoid biosynthesis. Toxic intermedia...
  
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Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

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A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

Munmun Ghosh,
Valmik S. Shinde and
Magnus Rueping

Review
Published 13 Nov 2019

616 Accesses

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1. Graphical Abstract
2. Figure 1: General classification of asymmetric electroorganic reactions.
  
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3. Scheme 1: Asymmetric reduction of 4-acetylpyridine using a modified graphite cathode.
  
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4. Scheme 2: Asymmetric hydrogenation of ketones using Raney nickel powder electrodes modified with optically ac...
  
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5. Scheme 3: Asymmetric reduction of prochiral activated olefins with a poly-ʟ-valine-coated graphite cathode.
  
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6. Scheme 4: Asymmetric reduction of prochiral carbonyl compounds, oximes and gem-dibromides on a poly-ʟ-valine-...
  
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7. Scheme 5: Asymmetric hydrogenation of prochiral ketones with poly[Ru^III(L)₂Cl₂]⁺-modified carbon felt cathode...
  
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8. Scheme 6: Asymmetric hydrogenation of α-keto esters using chiral polypyrrole film-coated cathode incorporated...
  
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9. Scheme 7: Quinidine and cinchonidine alkaloid-induced asymmetric electroreduction of acetophenone.
  
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10. Scheme 8: Asymmetric electroreduction of 4- and 2-acetylpyridines at a mercury cathode in the presence of a c...
  
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11. Scheme 9: Enantioselective reduction of 4-methylcoumarin in the presence of catalytic yohimbine.
  
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12. Scheme 10: Cinchonine-induced asymmetric electrocarboxylation of 4-methylpropiophenone.
  
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13. Scheme 11: Enantioselective hydrogenation of methyl benzoylformate using an alkaloid entrapped silver cathode.
  
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14. Scheme 12: Alkaloid-induced enantioselective hydrogenation using a Cu nanoparticle cathode.
  
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15. Scheme 13: Alkaloid-induced enantioselective hydrogenation of aromatic ketones using a bimetallic Pt@Cu cathod...
  
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16. Scheme 14: Enantioselective reduction of ketones at mercury cathode using N,N'-dimethylquininium tetrafluorobo...
  
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17. Scheme 15: Asymmetric synthesis of an amino acid using an electrode modified with amino acid oxidase and elect...
  
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18. Scheme 16: Asymmetric oxidation of p-tolyl methyl sulfide using chemically modified graphite anode.
  
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19. Scheme 17: Asymmetric oxidation of unsymmetric sulfides using poly(amino acid)-coated electrodes.
  
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20. Scheme 18: Enantioselective, electocatalytic oxidative coupling on TEMPO-modified graphite felt electrode in t...
  
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21. Scheme 19: Asymmetric electrocatalytic oxidation of racemic alcohols on a TEMPO-modified graphite felt electro...
  
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22. Scheme 20: Asymmetric electrocatalytic lactonization of diols on TEMPO-modified graphite felt electrodes.
  
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23. Scheme 21: Asymmetric electrochemical pinacolization in a chiral solvent.
  
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24. Scheme 22: Asymmetric electroreduction using a chiral supporting electrolyte.
  
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25. Scheme 23: Asymmetric anodic oxidation of enol acetates using chiral supporting electrolytes.
  
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26. Scheme 24: Kinetic resolution of primary amines using a chiral N-oxyl radical mediator.
  
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27. Scheme 25: Chiral N-oxyl-radical-mediated kinetic resolution of secondary alcohols via electrochemical oxidati...
  
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28. Scheme 26: Chiral iodoarene-mediated asymmetric electrochemical lactonization.
  
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29. Scheme 27: Os-catalyzed electrochemical asymmetric dihydroxylation of olefins using the Sharpless ligand and i...
  
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30. Scheme 28: Asymmetric electrochemical epoxidation of olefins catalyzed by a chiral Mn-salen complex.
  
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31. Scheme 29: Asymmetric electrooxidation of 1,2-diols, and amino alcohols using a chiral copper catalyst.
  
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32. Scheme 30: Mechanism of asymmetric electrooxidation of 1,2-diols, and amino alcohols using a chiral copper cat...
  
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33. Scheme 31: Enantioselective electrocarboxylation catalyzed by an electrogenerated chiral [Co^I(salen)]⁻ complex....
  
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34. Scheme 32: Asymmetric oxidative cross coupling of 2-acylimidazoles with silyl enol ethers.
  
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35. Scheme 33: Ni-catalyzed asymmetric electroreductive cleavage of allylic β-keto ester 89.
  
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36. Scheme 34: Asymmetric alkylation using a combination of electrosynthesis and a chiral Ni catalyst.
  
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37. Scheme 35: Mechanism of asymmetric alkylation using a combination of electrosynthesis and a chiral Ni catalyst....
  
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38. Scheme 36: Asymmetric epoxidation by electrogenerated percarbonate and persulfate ions in the presence of chir...
  
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39. Scheme 37: α-Oxyamination of aldehydes via anodic oxidation catalyzed by chiral secondary amines.
  
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40. Scheme 38: The α-alkylation of aldehydes via anodic oxidation catalyzed by chiral secondary amines.
  
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41. Scheme 39: Mechanism of α-alkylation of aldehydes via anodic oxidation catalyzed by chiral secondary amines.
  
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42. Scheme 40: Electrochemical chiral secondary amine-catalyzed intermolecular α-arylation of aldehydes.
  
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43. Scheme 41: Mechanism of electrochemical chiral secondary amine-catalyzed intermolecular α-arylation of aldehyd...
  
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44. Scheme 42: Asymmetric cross-dehydrogenative coupling of tertiary amines with simple ketones via an electrochem...
  
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45. Scheme 43: Electroenzymatic asymmetric reduction using enoate reductase.
  
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46. Scheme 44: Assymetric reduction using alcohol dehydrogenase as the electrocatalyst.
  
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47. Scheme 45: Asymmetric electroreduction catalyzed by thermophilic NAD-dependent alcohol dehydrogenase.
  
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48. Scheme 46: Asymmetric epoxidation of styrene by electrochemical regeneration of flavin-dependent monooxygenase....
  
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49. Scheme 47: Asymmetric electroreduction using a chloroperoxidase catalyst.
  
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50. Scheme 48: Asymmetric electrochemical transformation mediated by hydrophobic vitamin B12.
  
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51. Scheme 49: Diastereoselective cathodic reduction of phenylglyoxalic acids substituted with amines as chiral au...
  
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52. Scheme 50: Ni-catalyzed asymmetric electroreductive cross coupling of aryl halides with α-chloropropanoic acid...
  
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53. Scheme 51: Electrochemical Mannich addition of silyloxyfuran to in situ-generated N-acyliminium ions.
  
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54. Scheme 52: Stereoselective electroreductive homodimerization of cinnamates attached to a camphor-derived chira...
  
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55. Scheme 53: Diastereoselective electrochemical carboxylation of chiral α-bromocarboxylic acid derivatives.
  
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56. Scheme 54: Electrocatalytic stereoselective conjugate addition of chiral β-dicarbonyl compounds to methyl viny...
  
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57. Scheme 55: Stereoselective electrochemical carboxylation of chiral cinnamic acid derivatives under a CO₂ atmos...
  
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58. Scheme 56: Electrochemical diastereoselective α-alkylation of pyrrolidines attached with phosphorus-derived ch...
  
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59. Scheme 57: Electrogenerated cyanomethyl anion-induced synthesis of chiral cis-β-lactams from amides bearing ch...
  
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60. Scheme 58: Diastereoselective anodic oxidation followed by intramolecular cyclization of ω-hydroxyl amides bea...
  
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61. Scheme 59: Electrochemical deprotonation of Ni(II) glycinate containing (S)-BPB as a chiral auxiliary: diaster...
  
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62. Scheme 60: Enantioselective electroreductive coupling of diaryl ketones with α,β-unsaturated carbonyl compound...
  
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63. Scheme 61: Asymmetric total synthesis of ropivacaine and its analogues using a electroorganic reaction as a ke...
  
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64. Scheme 62: Asymmetric total synthesis of (−)-crispine A and its natural enantiomer via anodic cyanation of tet...
  
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65. Scheme 63: Asymmetric oxidative electrodimerization of cinnamic acid derivatives as key step for the synthesis...
  
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Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

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A combinatorial approach to improving the performance of azoarene photoswitches

Joaquin Calbo,
Aditya R. Thawani,
Rosina S. L. Gibson,
Andrew J. P. White and
Matthew J. Fuchter

Full Research Paper
Published 14 Nov 2019

534 Accesses

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1. Graphical Abstract
2. Figure 1: a) Tetra ortho-substituted azobenzenes represent a significant advance in terms of Z-isomer stabili...
  
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3. Figure 2: Minimum-energy geometry calculated for a) the Z-isomer ground state and b) the transition states wi...
  
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4. Figure 3: Noncovalent index (NCI) surfaces calculated for representative pyrrolidine-based ortho-substituted ...
  
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5. Figure 4: Noncovalent index (NCI) surfaces and θ dihedral angles (in red) calculated for the minimum-energy g...
  
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6. Figure 5: Description of the lowest-lying n–π* excitation for the Z-isomers of halogenated 4pzH-F2 and 4pzH-C...
  
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7. Figure 6: Description of the lowest-lying n–π* excitation for the E-isomers of halogenated 4pzH-F2 and 4pzH-C...
  
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8. Figure 7: X-ray structures of 4pzMe-F2 (left), 4pzH-F2 (middle) and 4pzMe-OMe2 (right).
  
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9. Figure 8: Experimental UV–vis spectra of 4pzMe-F2, 4pzMe-Cl2, 4pzMe-OMe2 and 4pzH-F2 in MeCN at 25 µM.
  
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Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

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