Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

Chi-Tung Yeung,
Wesley Ting Kwok Chan,
Wai-Sum Lo,
Ga-Lai Law and
Wing-Tak Wong

Full Research Paper
Published 18 Apr 2019

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1. Graphical Abstract
2. Scheme 1: Chiral biphenyl diol organocatalysts 1–6.
  
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3. Scheme 2: Synthesis of 3.
  
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4. Figure 1: (a) Single crystal X-ray structure of 3: showing intra- and intermolecular hydrogen bonds (green da...
  
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5. Scheme 3: Synthesis of 4.
  
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6. Scheme 4: Synthesis of 6.
  
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7. Figure 2: X-ray crystal structure of (P)-(S,S)-6 at two different orientations to show (a) P atropselectiviti...
  
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Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

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Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

Fangfang Pan,
Mohadeseh Dashti,
Michael R. Reynolds,
Kari Rissanen,
John F. Trant and
Ngong Kodiah Beyeh

Full Research Paper
Published 18 Apr 2019

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1. Graphical Abstract
2. Figure 1: Tetravalent XB acceptor, Hex-NARBr 1, Cy-NARCl 2, divalent XB donor DIOFB, and guests MeCN, MeOH an...
  
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3. Figure 2: The previously reported halogen-bonded complexes CHCl₃@1&DIOFB (a), and MeOH@1&DIOFB (b). (c)The fi...
  
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4. Figure 3: The two dimerization modes in the MeOH-MeCN@1&DIOFB complex. In both modes, the cavities are shown ...
  
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5. Figure 4: (a) The halogen bonding (blue broken lines), hydrogen bonding (red broken lines) and the host–guest...
  
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6. Figure 5: ¹⁹F NMR in CDCl₃ at 298 K of: a) DIOFB (10 mM); b) 1:2 mixture of DIOFB and 1; 1:2:1 mixture of DIO...
  
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7. Figure 6: ¹H NMR in CDCl₃ at 298 K of: a) 1 (10 mM), b) 1:2 mixture of 1 and DIOFB, c) 1:2:1 mixture of 1, DI...
  
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Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

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Towards the preparation of synthetic outer membrane vesicle models with micromolar affinity to wheat germ agglutinin using a dialkyl thioglycoside

Dimitri Fayolle,
Nathalie Berthet,
Bastien Doumeche,
Olivier Renaudet,
Peter Strazewski and
Michele Fiore

Full Research Paper
Published 17 Apr 2019

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1. Graphical Abstract
2. Figure 1: Structure of the β-thiols 1a and 1b and of the commercial alkenes 2a and 2b.
  
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3. Scheme 1: Synthesis of the n-alkyl thioglycosides 3–5, 7 and 8. Detailed reaction conditions are reported in ...
  
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4. Scheme 2: Synthesis of the lipophilic scaffold 6; DMAP = N,N-dimethylaminopyridine.
  
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5. Figure 2: Periodic monitoring by ¹H NMR (300 MHz, DMF-d₇) of the formation of product 8 from a mixture compou...
  
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6. Figure 3: Micrographs of giant vesicles and lipid aggregates obtained from the gentle hydration (in PBS, pH 7...
  
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7. Figure 4: A simplified (and not in scale) representation of the ELLA assay, to study the interaction between ...
  
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8. Figure 5: Inhibition curves for the binding of WGA-HRP to PAA-GlcNAc by D-GlcNAc The symbols (■), () and (○) ...
  
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9. Figure 6: Main poses obtained from docking experiments. WGA (PDB 2UVO) surface is shown in white for monomer ...
  
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Beilstein J. Org. Chem. 2019, 15, 937–946, doi:10.3762/bjoc.15.90

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An anomalous addition of chlorosulfonyl isocyanate to a carbonyl group: the synthesis of ((3aS,7aR,E)-2-ethyl-3-oxo-2,3,3a,4,7,7a-hexahydro-1H-isoindol-1-ylidene)sulfamoyl chloride

Aytekin Köse,
Aslı Ünal,
Ertan Şahin,
Uğur Bozkaya and
Yunus Kara

Letter
Published 16 Apr 2019

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1. Graphical Abstract
2. Scheme 1: The reaction of CSI with olefins.
  
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3. Figure 1: The dipolar intermediate formed in the reaction of CSI with olefins.
  
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4. Scheme 2: The synthesis of imide 9.
  
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5. Scheme 3: The synthesis of ylidene sulfamoyl chloride 10.
  
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6. Figure 2: (a) Molecular structure of racemic molecule 10 (asymmetric unit). Thermal ellipsoids are drawn at t...
  
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7. Scheme 4: Mechanism for the formation of ylidenesulfamoyl chloride 10.
  
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8. Figure 3: Relative energy profile of the reaction mechanism shown in Scheme 4.
  
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Beilstein J. Org. Chem. 2019, 15, 931–936, doi:10.3762/bjoc.15.89

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Synthesis of (macro)heterocycles by consecutive/repetitive isocyanide-based multicomponent reactions

Angélica de Fátima S. Barreto and
Carlos Kleber Z. Andrade

Review
Published 15 Apr 2019

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1. Graphical Abstract
2. Scheme 1: Comparison between a normal sequential reaction and an MCR.
  
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3. Scheme 2: Synthesis of tetrazoles and hydantoinimide derivatives by consecutive Ugi reactions [17].
  
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4. Scheme 3: Synthesis of tetrazole-ketopiperazines by two consecutive Ugi reactions [19].
  
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5. Scheme 4: Synthesis of acylhydrazino bis(1,5-disubstituted tetrazoles) through two hydrazine-Ugi-azide reacti...
  
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6. Scheme 5: Synthesis of substituted α-aminomethyltetrazoles through two consecutive Ugi reactions (U-4CR and U...
  
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7. Scheme 6: Synthesis of tetrazole peptidomimetics by direct use of amino acids in two consecutive Ugi reaction...
  
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8. Scheme 7: One-pot 8CR based on 3 sequential IMCRs [25].
  
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9. Scheme 8: Combination of IMCRs for the synthesis of substituted 2H-imidazolines [25].
  
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10. Scheme 9: 6CR involving a tandem combination of Groebke–Blackburn–Bienaymé and Ugi reaction for the synthesis...
  
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11. Scheme 10: 5CR involving a tandem combination of Groebke–Blackburn–Bienaymé and Passerini reaction for the syn...
  
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12. Scheme 11: Synthesis of tubugis via three consecutive IMCRs [27].
  
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13. Scheme 12: Synthesis of telaprevir through consecutive IMCRs [28].
  
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14. Scheme 13: Another synthesis of telaprevir through consecutive IMCRs [29].
  
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15. Scheme 14: a) Synthetic sequence for accessing diverse macrocycles containing the tetrazole nucleus by the uni...
  
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16. Scheme 15: a) Synthetic sequence for the tetrazolic macrocyclic depsipeptides using a combination of two IMCRs...
  
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17. Scheme 16: Synthesis of cyclic pentapeptoids by consecutive Ugi reactions [32].
  
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18. Scheme 17: Synthesis of a cyclic pentapeptoid by consecutive Ugi reactions [32].
  
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19. Scheme 18: MW-mediated synthesis of a cyclopeptoid by consecutive Ugi reactions [33].
  
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20. Scheme 19: Synthesis of six cyclic pentadepsipeptoids via consecutive isocyanide-based IMCRs [34].
  
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21. Scheme 20: Microwave-mediated synthesis of a cyclic heptapeptoid through four consecutive IMCRs [35].
  
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22. Scheme 21: Macrocyclization of bifunctional building blocks containing diacid/diisonitrile and diamine/diisoni...
  
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23. Scheme 22: Synthesis of steroid-biaryl ether hybrid macrocycles by MiBs [38].
  
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24. Scheme 23: Synthesis of biaryl ether-containing macrocycles by MiBs [39].
  
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25. Scheme 24: Synthesis of natural product-inspired biaryl ether-cyclopeptoid macrocycles [40].
  
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26. Scheme 25: Synthesis of cholane-based hybrid macrolactams by MiBs [41].
  
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27. Scheme 26: Synthesis of macrocyclic oligoimine-based DCL using the Ugi-4CR-based quenching approach [42].
  
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28. Scheme 27: Dye-modified and photoswitchable macrocycles by MiBs [43].
  
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29. Scheme 28: Synthesis of nonsymmetric cryptands by two sequential double Ugi-4CR-based macrocyclizations [44].
  
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30. Scheme 29: Synthesis of steroid–aryl hybrid cages by sequential 2- and 3-fold Ugi-4CR-based macrocyclizations [46]....
  
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31. Scheme 30: Ugi-MiBs approach towards natural product-like macrocycles [47].
  
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32. Scheme 31: a) Bidirectional macrocyclization of peptides by double Ugi reaction. b) Ugi-4CR for the generation...
  
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33. Scheme 32: MiBs based on the Passerini-3CR for the synthesis of macrolactones [49].
  
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34. Scheme 33: Template-driven approach for the synthesis of macrotricycles 170 [50].
  
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Beilstein J. Org. Chem. 2019, 15, 906–930, doi:10.3762/bjoc.15.88

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Easy, efficient and versatile one-pot synthesis of Janus-type-substituted fullerenols

Marius Kunkel and
Sebastian Polarz

Letter
Published 12 Apr 2019

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1. Graphical Abstract
2. Scheme 1: Reaction scheme for the one-pot reaction of C₆₀Cl₆ to produce Janus-type fullerenols (OH)_19+/−3C₆₀(...
  
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3. Figure 1: Characterization of fullerenol amphiphile with substituent 1. a) ESIMS in positive mode, molecular ...
  
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Beilstein J. Org. Chem. 2019, 15, 901–905, doi:10.3762/bjoc.15.87

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Mechanochemistry of supramolecules

Anima Bose and
Prasenjit Mal

Review
Published 12 Apr 2019

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1. Graphical Abstract
2. Figure 1: A generalized overview of coordination-driven self-assembly.
  
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3. Figure 2: Examples of self-assembly or self-sorting and subsequent substitution.
  
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4. Figure 3: Synthesis of salen-type ligand followed by metal-complex formation in the same pot [55].
  
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5. Figure 4: Otera’s solvent-free approach by which the formation of self-assembled supramolecules could be acce...
  
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6. Figure 5: Synthesis of a Pd-based metalla-supramolecular assembly through mechanochemical activation for C–H-...
  
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7. Figure 6: a) Schematic representation for the construction of a [2]rotaxane. b) Chiu’s ball-milling approach ...
  
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8. Figure 7: Mechanochemical synthesis of the smallest [2]rotaxane.
  
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9. Figure 8: Solvent-free mechanochemical synthesis of pillar[5]arene-containing [2]rotaxanes [61].
  
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10. Figure 9: Mechanochemical liquid-assisted one-pot two-step synthesis of [2]rotaxanes under high-speed vibrati...
  
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11. Figure 10: Mechanochemical (ball-milling) synthesis of molecular sphere-like nanostructures [63].
  
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12. Figure 11: High-speed vibration milling (HSVM) synthesis of boronic ester cages of type 22 [64].
  
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13. Figure 12: Mechanochemical synthesis of borasiloxane-based macrocycles.
  
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14. Figure 13: Mechanochemical synthesis of 2-dimensional aromatic polyamides.
  
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15. Figure 14: Nitschke’s tetrahedral Fe(II) cage 25.
  
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16. Figure 15: Mechanochemical one-pot synthesis of the 22-component [Fe₄(AD₂)₆]⁴⁻ 26, 11-component [Fe₂(BD₂)₃]²⁻ ...
  
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17. Figure 16: a) Subcomponent synthesis of catalyst and reagent and b) followed by multicomponent reaction for sy...
  
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18. Figure 17: A dynamic combinatorial library (DCL) could be self-sorted to two distinct products.
  
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19. Figure 18: Mechanochemical synthesis of dynamic covalent systems via thermodynamic control.
  
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20. Figure 19: Preferential formation of hexamer 33 under mechanochemical shaking via non-covalent interactions of...
  
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21. Figure 20: Anion templated mechanochemical synthesis of macrocycles cycHC[n] by validating the concept of dyna...
  
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22. Figure 21: Hydrogen-bond-assisted [2 + 2]-cycloaddition reaction through solid-state grinding. Hydrogen-bond d...
  
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23. Figure 22: Formation of the cage and encapsulation of [2.2]paracyclophane guest molecule in the cage was done ...
  
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24. Figure 23: Formation of the 1:1 complex C₆₀–tert-butylcalix[4]azulene through mortar and pestle grinding of th...
  
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25. Figure 24: Formation of a 2:2 complex between the supramolecular catalyst and the reagent in the transition st...
  
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26. Figure 25: Halogen-bonded co-crystals via a) I···P, b) I···As, and c) I···Sb bonds [112].
  
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27. Figure 26: Transformation of contact-explosive primary amines and iodine(III) into a successful chemical react...
  
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28. Figure 27: Undirected C–H functionalization by using the acidic hydrogen to control basicity of the amines [114]. a...
  
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Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

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Efficient synthesis of pyrazolopyridines containing a chromane backbone through domino reaction

Razieh Navari,
Saeed Balalaie,
Saber Mehrparvar,
Fatemeh Darvish,
Frank Rominger,
Fatima Hamdan and
Sattar Mirzaie

Full Research Paper
Published 11 Apr 2019

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1. Graphical Abstract
2. Figure 1: Selected examples of bioactive molecules based on the pyrazolopyridine framework.
  
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3. Scheme 1: Synthesis of pyrazolopyridines containing chromone 4a–m through a multicomponent reaction.
  
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4. Figure 2: ORTEP Structure of compound 4a and intermolecular hydrogen bonding; the ellipsoid probability level...
  
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5. Figure 3: Structures of synthesized pyrazolopyridines 4a–m. Reaction conditions: 3-formylchromone derivatives...
  
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6. Scheme 2: The proposed mechanism for the synthesis of pyrazolopyridines derivatives 4a–m and 5a–d.
  
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7. Figure 4: Structures of synthesized compounds 5a–d.
  
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Beilstein J. Org. Chem. 2019, 15, 874–880, doi:10.3762/bjoc.15.85

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Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

Ayato Yamada,
Manabu Abe,
Yoshinobu Nishimura,
Shoji Ishizaka,
Masashi Namba,
Taku Nakashima,
Kiyofumi Shimoji and
Noboru Hattori

Full Research Paper
Published 10 Apr 2019

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1. Graphical Abstract
2. Scheme 1: Photochemical generation of TEMPO radical.
  
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3. Scheme 2: Synthesis of caged nitroxides 2a and 2b.
  
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4. Figure 1: Photochemical generation of TEMPO from 2a and 2b. EPR spectra acquired during the photolysis of 2a ...
  
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5. Figure 2: Time profile for photochemical generation of TEMPO radical from 2 (5 mM) at ≈298 K in benzene: (a) ...
  
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6. Scheme 3: Photochemical generation of TEMPO radical and photoproducts 6 and 7 under air atmosphere.
  
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7. Figure 3: Time profile, ln([2a]/[2a]₀) versus irradiation time, of two-photon uncaging reaction of TEMPO in t...
  
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8. Figure 4: ESR spectra acquired during the photolysis of 2a (5 mM) in benzene using 365 nm light.
  
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9. Scheme 4: Isodesmic reaction from BRa and 5b to 5a and BRb.
  
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10. Figure 5: Irradiation time-dependent decline in viability of LLC cells with compound 2a.
  
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11. Figure 6: Detection of intracellular ROS only in irradiated LLC cells with 2a-containing medium.
  
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Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

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An efficient synthesis of the guaiane sesquiterpene (−)-isoguaiene by domino metathesis

Yuzhou Wang,
Ahmed F. Darweesh,
Patrick Zimdars and
Peter Metz

Full Research Paper
Published 09 Apr 2019

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1. Graphical Abstract
2. Figure 1: Structures of the sesquiterpene (−)-isoguaiene (1) and the trisnorsesquiterpene clavukerin A (2).
  
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3. Scheme 1: Retrosynthetic analysis for (−)-isoguaiene (1).
  
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4. Scheme 2: Synthesis of 1 by relay metathesis of trienyne 3. a) HC(OMe)₃, 4 mol % LiBF₄, MeOH, reflux, 80%; b)...
  
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5. Scheme 3: Attempted preparation of 1 by domino metathesis of enediyne 7. a) (i) O₃, CH₂Cl₂, MeOH, pyridine, −...
  
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6. Scheme 4: Conversion of 28 to 1 by relay metathesis of dienediyne 8. a) (i) 21, THF, rt to reflux, (ii) BuLi,...
  
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Beilstein J. Org. Chem. 2019, 15, 858–862, doi:10.3762/bjoc.15.83

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Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides

Maryam Khalesi,
Azim Ziyaei Halimehjani and
Jürgen Martens

Full Research Paper
Published 04 Apr 2019

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1. Graphical Abstract
2. Scheme 1: Synthesis of amino acid-based isocyanides starting from α-amino acids.
  
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3. Scheme 2: Synthesis of pseudo-peptides using levulinic acid, isocyanide esters and amines.
  
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4. Figure 1: Synthesis of functionalized 5-membered lactams using Ugi reaction. ^aIsolated yield for mixture of d...
  
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5. Scheme 3: Proposed mechanism for Ugi-4C-3CR.
  
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6. Figure 2: ORTEP representation of compound (R*,S*)-4a with thermal ellipsoids at 50% probability. Opposite en...
  
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Beilstein J. Org. Chem. 2019, 15, 852–857, doi:10.3762/bjoc.15.82

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Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

Jennifer Klose,
Tobias Severin,
Peter Hahn,
Alexander Jeremies,
Jens Bergmann,
Daniel Fuhrmann,
Jan Griebel,
Bernd Abel and
Berthold Kersting

Full Research Paper
Published 03 Apr 2019

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1. Graphical Abstract
2. Figure 1: Left: Mixed ligand complexes of the type [M₂L(μ-L')]ⁿ⁺ supported by the macrocyclic ligand H₂L (M =...
  
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3. Figure 2: Synthesized compounds and their labels.
  
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4. Scheme 1: Synthesis of complexes 1–9.
  
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5. Figure 3: ¹H NMR spectrum of 6 in CD₃CN at 295 K (1.0–8.0 ppm). The resonances and assignments are listed in Table 2...
  
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6. Figure 4: Structure of the [Zn₂L(μ-azo-OH)]⁺ cation in crystals of [Zn₂L(μ-azo-OH)][Zn₂L(μ-azo-O)]·4MeCN·3H₂O...
  
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7. Figure 5: Space filling representation of the packing of two symmetry-related [Zn₂L(μ-azo-NMe₂)]⁺ cations in ...
  
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8. Figure 6: Structure of the [Cd₂L(μ-azo-NMe₂)]⁺ cation in crystals of [Cd₂L(μ-azo-NMe₂)]ClO₄·0.5MeOH (6·0.5MeO...
  
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9. Figure 7: Space filling representation of the packing of four [Cd₂L(μ-azo-NMe₂)]⁺ cations in crystals of 6·0....
  
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10. Figure 8: Structures of the two crystallographically independent [Ni₂L(μ-azo-NMe₂)]⁺ cations A (left) and B (...
  
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11. Figure 9: Left: ORTEP representation of the molecular structure of the [Cd₂L(μ-azo-CO₂Me)]⁺ cation in crystal...
  
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12. Figure 10: Plots of the effective magnetic moment μ_eff for 2 (open circles), 4 (open squares), and 7 (open tri...
  
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13. Figure 11: UV–vis spectra of Hazo-H (red line), [Cd₂L(μ-Cl)](ClO₄) (black line) and [Cd₂L(μ-azo-H)]ClO₄ (1, bl...
  
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14. Figure 12: UV–vis spectra of Hazo-NMe₂ (red line), [Ni₂L(μ-Cl)](ClO₄) (black line) and [Ni₂L(μ-azo-NMe₂)]ClO₄ (...
  
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15. Figure 13: UV–vis spectra of solutions of [Cd₂L(μ-azo-H)]ClO₄ (1) in acetonitrile irradiated with a UV LED lam...
  
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16. Scheme 2: Cis/trans isomerization process of the bound azo-carboxylato co-ligand in [Cd₂L(μ-azo-H)]ClO₄ (1) i...
  
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Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

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New α- and β-cyclodextrin derivatives with cinchona alkaloids used in asymmetric organocatalytic reactions

Iveta Chena Tichá,
Simona Hybelbauerová and
Jindřich Jindřich

Full Research Paper
Published 01 Apr 2019

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1. Graphical Abstract
2. Figure 1: Schematic cone-shaped (a) and structure representations (b) of α-CD (six glucopyranoside units) and...
  
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3. Figure 2: Common cinchona alkaloids (cinchonine, cinchonidine, quinine, quinidine).
  
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4. Scheme 1: CuAAC click reaction of propargylated cinchona alkaloids 3a–d with 6^I-azido-6^I-deoxy-α-CD (1) and 6^I...
  
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5. Scheme 2: CuAAC click reaction of per-Me-N₃-α-CD (6) or per-Me-N₃-β-CD (7) and propargylated cinchona alkaloi...
  
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6. Scheme 3: Synthesis of difunctionalized α-CD 11 with quinine moieties.
  
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7. Figure 3: Representative ¹H NMR spectrum of the non-methylated quinidine–α-CD derivative 4d.
  
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8. Figure 4: Representative ¹³C NMR spectrum and parts of the HMBC spectrum of the non-methylated quinidine–α-CD...
  
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9. Scheme 4: AAA reaction of MBH carbamate 12 catalyzed by the prepared CD derivatives 4a–d, 5a–d, 8a–d, 9a–d, 11...
  
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Beilstein J. Org. Chem. 2019, 15, 830–839, doi:10.3762/bjoc.15.80

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Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines

Camila B. Francisco,
Cleverton S. Fernandes,
Ulisses Z. de Melo,
Roberto Rittner,
Gisele F. Gauze and
Ernani A. Basso

Full Research Paper
Published 01 Apr 2019

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1. Graphical Abstract
2. Figure 1: Conformations of cis-2-halocyclohexylamines, where X = F, Cl, Br and I.
  
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3. Figure 2: Variable-temperature ¹H NMR spectra (500.13 MHz) for cis-2-chlorocyclohexylamine in dichloromethane-...
  
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4. Figure 3: Potential energy surfaces (PESs) for cis-2-halocyclohexylamines for the C2–C1–N–H dihedral angle ro...
  
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5. Figure 4: Populations of rotamers a, gX e gH in ae (top) and ea (bottom) conformers of cis-2-halocyclohexylam...
  
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6. Figure 5: Nitrogen lone pair in rotamers gX (ae) and a (ea) oriented towards the halogen, making these rotame...
  
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7. Figure 6: PCA for 22 variables corresponding to the hyperconjugative interactions for all rotamers in ae and ...
  
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8. Figure 7: Sum of bonding (donor) and antibonding (acceptor) orbitals interactions of C1–H, C2–X and C3–H_ax bo...
  
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9. Figure 8: Orbitals overlap of σ_C1–H → σ*_C2–X (left) and σ_C3–Hax → σ*_C2–X (right) hyperconjugations in ea conf...
  
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Beilstein J. Org. Chem. 2019, 15, 818–829, doi:10.3762/bjoc.15.79

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Synthesis of acylglycerol derivatives by mechanochemistry

Karen J. Ardila-Fierro,
Andrij Pich,
Marc Spehr,
José G. Hernández and
Carsten Bolm

Full Research Paper
Published 29 Mar 2019

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1. Graphical Abstract
2. Figure 1: Biologically relevant molecules made, used or derivatized by mechanochemistry.
  
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3. Figure 2: Isomeric diacyl-sn-glycerols (DAGs).
  
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4. Scheme 1: Synthetic route to access protected DAGs; PG = protecting group.
  
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5. Scheme 2: Protection of glycidol (1) with TBDMSCl in the ball mill. MM = mixer mill, PBM = planetary ball mil...
  
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6. Scheme 3: Cobalt-catalyzed epoxide ring-opening in the ball mill.
  
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7. Scheme 4: Mechanosynthesis of DAGs 5.
  
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8. Scheme 5: Conjugation of DAG 5a with 7-hydroxycoumarin (9).
  
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9. Figure 3: UV−vis spectra of DAG 6a (dotted line) and conjugated DAGs 10a and 10a’ as a mixture (10a/10a’ 72:2...
  
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Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

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An improved synthesis of adefovir and related analogues

David J. Jones,
Eileen M. O’Leary and
Timothy P. O’Sullivan

Full Research Paper
Published 29 Mar 2019

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1. Graphical Abstract
2. Figure 1: Adefovir (1) and its prodrug 2.
  
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3. Scheme 1: Literature syntheses of 1.
  
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4. Figure 2: Retrosynthetic analysis of 6 to synthons 9 and 10.
  
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5. Scheme 2: Forward synthesis of 6 from 9 and 10.
  
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6. Figure 3: Retrosynthesis of 6 to synthons 14 and 3.
  
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7. Scheme 3: Application of related alkyl iodide 15 [52].
  
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8. Scheme 4: Synthesis of 6 and 20 via iodide 14.
  
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9. Scheme 5: Synthesis of phosphonate 6 using novel salt 21.
  
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10. Scheme 6: Application of iodide 14 in the synthesis of adefovir analogues.
  
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11. Figure 4: HMBC spectrum confirms N7-selectivity for the major product 29.
  
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12. Scheme 7: Attempted synthesis of adefovir dipivoxil (2) exploiting phosphonate 33.
  
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Beilstein J. Org. Chem. 2019, 15, 801–810, doi:10.3762/bjoc.15.77

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A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade

Hong Yan,
Zhong-Yi Mao,
Zhong-Wei Hou,
Jinshuai Song and
Hai-Chao Xu

Letter
Published 28 Mar 2019

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1. Graphical Abstract
2. Scheme 1: Reaction design.
  
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3. Scheme 2: Scope of electrochemical synthesis of axially chiral biaryls. Reaction conditions: undivided cell, 2...
  
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4. Scheme 3: Proposed reaction mechanism for the electrochemical synthesis of 3a.
  
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5. Scheme 4: Computation investigation on the vinyl radical cyclization. DFT (M06-2X/6-31G*) calculated energeti...
  
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Beilstein J. Org. Chem. 2019, 15, 795–800, doi:10.3762/bjoc.15.76

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Stereochemical investigations on the biosynthesis of achiral (Z)-γ-bisabolene in Cryptosporangium arvum

Jan Rinkel and
Jeroen S. Dickschat

Letter
Published 27 Mar 2019

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1. Graphical Abstract
2. Figure 1: Structures of achiral terpenes: (E)-β-farnesene (1), α-humulene (2), 1,8-cineol (3) and sodorifen (4...
  
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3. Figure 2: A) Total ion chromatogram of a hexane extract from the incubation of FPP with BbS and B) EI mass sp...
  
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4. Scheme 1: Cyclisation mechanism to 5 involving either the intermediates (R)-NPP and (S)-A (path A) or (S)-NPP...
  
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5. Figure 3: Total ion chromatograms of hexane extracts from incubation experiments with BbS and A) (R)-NPP, B) (...
  
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6. Figure 4: Hypothetical BbS active site comparable conformational folds of A) FPP, B) (R)- and C) (S)-NPP expl...
  
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Beilstein J. Org. Chem. 2019, 15, 789–794, doi:10.3762/bjoc.15.75

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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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Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

Kirill B. Polyanskii,
Kseniia A. Alekseeva,
Pavel V. Raspertov,
Pavel A. Kumandin,
Eugeniya V. Nikitina,
Atash V. Gurbanov and
Fedor I. Zubkov

Full Research Paper
Published 22 Mar 2019

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1. Graphical Abstract
2. Figure 1: Commercially available ruthenium catalysts for metathesis reactions.
  
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3. Figure 2: Retrosynthesis of the ruthenium catalysts.
  
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4. Scheme 1: Efficient multigram synthesis of N,N-dialkyl-2-vinylbenzylamines 4 (R¹X = Me₂SO₄, Et₂SO₄ or BnCl, s...
  
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5. Scheme 2: Synthesis of N-(2-ethenylbenzyl)heterocycles 5.
  
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6. Scheme 3: Synthesis of N-monoalkyl-2-vinylbenzylamine 7.
  
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7. Scheme 4: Synthesis of Hoveyda–Grubbs-type catalysts 11.
  
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8. Scheme 5: Synthesis of the “chloroform adduct” 9.
  
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9. Figure 3: Selected X-ray data for ruthenium complexes 11a–c. All hydrogen atoms were deleted for clarity (exc...
  
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10. Scheme 6: Catalytic activity of compounds 11 in the metathesis reactions.
  
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Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

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Solid-phase synthesis of biaryl bicyclic peptides containing a 3-aryltyrosine or a 4-arylphenylalanine moiety

Iteng Ng-Choi,
Àngel Oliveras,
Lidia Feliu and
Marta Planas

Full Research Paper
Published 22 Mar 2019

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1. Graphical Abstract
2. Figure 1: Structure of biaryl bicyclic peptides 1–3.
  
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3. Scheme 1: Retrosynthetic analysis for the biaryl bicyclic peptide 1.
  
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4. Scheme 2: Synthesis of the biaryl bicyclic peptide 1 incorporating a Phe-Phe linkage. Reagents and conditions...
  
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5. Scheme 3: Synthesis of the biaryl bicyclic peptide 2 incorporating a Phe-Tyr linkage. Reagents and conditions...
  
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6. Scheme 4: Synthesis of the biaryl bicyclic peptide 3 incorporating a Tyr-Tyr linkage. Reagents and conditions...
  
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Beilstein J. Org. Chem. 2019, 15, 761–768, doi:10.3762/bjoc.15.72

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Diastereo- and enantioselective preparation of cyclopropanol derivatives

Marwan Simaan and
Ilan Marek

Full Research Paper
Published 21 Mar 2019

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1. Graphical Abstract
2. Scheme 1: Various strategies leading to the formation of cyclopropanols.
  
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3. Scheme 2: General approach to the preparation of cyclopropanol and cyclopropylamine derivatives.
  
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4. Figure 1: Prerequisite for a regio- and diastereoselective carbometalation.
  
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5. Scheme 3: Preparation of cyclopropenyl methyl ethers 3a–d.
  
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6. Scheme 4: Regio- and diastereoselective carbocupration of cyclopropenyl methyl ethers 3a,c.
  
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7. Scheme 5: Diastereoselective formation of cyclopropanols.
  
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8. Scheme 6: Diastereoselective carbometalation/oxidation of nonfunctionalized cyclopropenes 6.
  
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9. Scheme 7: Preparation of diastereoisomerically pure and enantioenriched cyclopropanols and cyclopropylamines.
  
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Beilstein J. Org. Chem. 2019, 15, 752–760, doi:10.3762/bjoc.15.71

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Tuning the stability of alkoxyisopropyl protection groups

Zehong Liang,
Henna Koivikko,
Mikko Oivanen and
Petri Heinonen

Full Research Paper
Published 21 Mar 2019

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1. Graphical Abstract
2. Figure 1: Reagents for acetal protections.
  
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3. Scheme 1: Synthesis of 2-alkoxyprop-2-yl-protected thymidines. Reagents and conditions (i) 7 equiv 1a–e, 0.5 ...
  
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4. Figure 2: Enol ether 8a: R¹ = TBS and 8b: R¹ = H.
  
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5. Scheme 2: Proposed acetal hydrolysis pathways.
  
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Beilstein J. Org. Chem. 2019, 15, 746–751, doi:10.3762/bjoc.15.70

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Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

Zhargolma B. Bazarova,
Ludmila S. Soroka,
Alex A. Lyapkov,
Мekhman S. Yusubov and
Francis Verpoort

Full Research Paper
Published 20 Mar 2019

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1. Graphical Abstract
2. Figure 1: Absorption spectra in the UV and visible spectral region: 1) bis(cyclopentadienyl)titan dichloride (...
  
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3. Figure 2: Absorption spectra in the visible spectral region: 1) Cp₂TiCl₂·AlEt₂Cl (toluene, 10 mmol/L, Ti/Al r...
  
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4. Figure 3: ¹Н NMR spectra of tricyclopentadiene (a) and the interaction product between Cp₂TiCl₂ and AlEt₂Cl w...
  
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5. Scheme 1: Mechanism of alkylation of Cp₂TiCl₂.
  
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6. Figure 4: Visible spectra of a mixture of Cp₂TiCl₂ and AlEt₂Cl as function of time.
  
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7. Figure 5: Thermometric curve of DCPD polymerization using the catalyst system based on Cp₂TiCl₂ (a) and its s...
  
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8. Scheme 2: The structures formed as a result of the cationic polymerization of dicyclopentadiene.
  
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9. Scheme 3: The units resulting from ROMP of dicyclopentadiene.
  
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10. Scheme 4: Mechanism of ROMP dicyclopentadiene.
  
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11. Figure 6: FTIR spectrum of PDCPD obtained in toluene with the catalyst system based on Cp₂TiCl₂ and AlEt₂Cl.
  
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12. Figure 7: ¹Н NMR spectrum of PDCPD obtained with the catalytic system based on Cp₂TiCl₂ and AlEt₂Cl.
  
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13. Figure 8: GPC traces for two samples of DCPD polymers obtained at a concentration of Cp₂TiCl₂/AlEt₂Cl complex...
  
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14. Figure 9: IR spectra of cationic polymerized dicyclopentadiene taken after certain periods of time exposed to...
  
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15. Figure 10: Correlation of intensities of vibrational bands at 1620 and 700 cm⁻¹ and layer exposure time in air...
  
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16. Figure 11: DSC exotherm for PDCPD subjected to air oxidation for 700 hours.
  
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17. Figure 12: DSC exotherm for PDCPD subjected to unexposed film: 1) in air atmosphere; 2) in argon.
  
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18. Scheme 5: Possible radical formation in the reaction (1).
  
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19. Scheme 6: The first step of the chain propagation.
  
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20. Figure 13: Dependence of intensities of adsorption bands at 1410 and 700 cm⁻¹ and dwell time of the layer in a...
  
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21. Figure 14: Semi-logarithmic kinetic curve of PDCPD oxidation in air (thin layer on silicon) with respect to in...
  
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22. Figure 15: The distribution of oxygen concentration in the polymer layer: 1 – a layer of oxidized cross-linked...
  
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23. Figure 16: Dependence of the ratio of adsorption bands at 1700 and 700 cm⁻¹ on the exposure time of the layer ...
  
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24. Figure 17: Infrared spectra (a) of products of cationic polymerization of DCPD, stabilized with an antioxidant...
  
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Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

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Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials

Widukind Moormann,
Daniel Langbehn and
Rainer Herges

Full Research Paper
Published 20 Mar 2019

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1. Graphical Abstract
2. Figure 1: (a) Isomerization of parent diazocine 1. Distances of carbon atoms para to the ethylene bridge were...
  
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3. Figure 2: Synthesized target diazocines 4–7 for applications in responsive materials.
  
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4. Scheme 1: Key reactions in diazocine synthesis.
  
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5. Scheme 2: Syntheses of the functionalized diazocines 4–7. Reaction conditions: i) Isobutylene, sulfuric acid,...
  
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6. Figure 3: UV–vis spectra of 3,3’-diaminodiazocine 2 (left), 3,3’-di(aminomethyl)diazocine 6a (center), and 3,...
  
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Beilstein J. Org. Chem. 2019, 15, 727–732, doi:10.3762/bjoc.15.68

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