Photocycloadditions and photorearrangements

Editor: Prof. Axel G. Griesbeck
Universität zu Köln

Organic synthesis using light as reagent and producing complex molecules from simple starting materials is realized in exemplary fashion in natural photosynthesis. Mankind still struggles for an efficient molecular system that mimics this natural process. In order to harvest light energy and to transform it into chemical energy, photochemical reactions must be studied and optimized for synthetic applications. Two major reaction paths that use electronic excitation are photocycloadditions and photochemical rearrangements. These reactions have been intensively investigated in recent decades.

See also the Thematic Series:
Organic synthesis using photoredox catalysis

Photocycloadditions and photorearrangements

Axel G. Griesbeck

Editorial
Published 26 Jan 2011

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Beilstein J. Org. Chem. 2011, 7, 111–112, doi:10.3762/bjoc.7.15

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Synthesis of 2a,8b-Dihydrocyclobuta[a]naphthalene-3,4-diones

Kerstin Schmidt and
Paul Margaretha

Full Research Paper
Published 13 Jul 2010

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1. Graphical Abstract
2. Scheme 1: Synthesis of 2a,8b-dihydrocyclobuta[a]naphthalene-3,4-diones.
  
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Beilstein J. Org. Chem. 2010, 6, No. 76, doi:10.3762/bjoc.6.76

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Heavy atom effects in the Paternò–Büchi reaction of pyrimidine derivatives with 4,4’-disubstituted benzophenones

Feng-Feng Kong,
Jian-Bo Wang and
Qin-Hua Song

Full Research Paper
Published 26 Jan 2011

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1. Graphical Abstract
2. Scheme 1: The Paternò–Büchi reaction of DMT/DMU with benzophenones to generate two regioisomeric photoproduct...
  
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3. Figure 1: The yield and the ratio of 2/3 at different reaction times in the Paternò–Büchi reaction of DMT wit...
  
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4. Figure 2: Eyring plots for the photoreaction of DMT with compounds 1b–e.
  
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5. Scheme 2: The formational processes of two regioisomers in the Paternò–Büchi reaction of DMT/DMU with benzoph...
  
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Beilstein J. Org. Chem. 2011, 7, 113–118, doi:10.3762/bjoc.7.16

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Synthesis of cationic dibenzosemibullvalene-based phase-transfer catalysts by di-π-methane rearrangements of pyrrolinium-annelated dibenzobarrelene derivatives

Heiko Ihmels and
Jia Luo

Full Research Paper
Published 26 Jan 2011

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1. Graphical Abstract
2. Scheme 1: Photorearrangements of dibenzobarrelene (DBB).
  
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3. Figure 1: General structure of pyrrolidinium-annelated dibenzosemibullvalenes (pyDBS).
  
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4. Scheme 2: Synthesis of dibenzobarrelene derivatives 2a–g.
  
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5. Scheme 3: Di-π-methane rearrangements of dibenzobarrelene derivatives 2a–f (counter ions omitted for clarity)....
  
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6. Scheme 4: Di-π-methane rearrangement of dibenzobarrelene derivative 2g.
  
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7. Scheme 5: Synthesis and solid-state photoreactivity of the sulfonate salt 2b-4.
  
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8. Scheme 6: Phase-transfer catalyzed alkylation reactions (see Table 1 for details).
  
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Beilstein J. Org. Chem. 2011, 7, 119–126, doi:10.3762/bjoc.7.17

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Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

Axel G. Griesbeck,
Marco Franke,
Jörg Neudörfl and
Hidehiro Kotaka

Full Research Paper
Published 26 Jan 2011

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1. Graphical Abstract
2. Scheme 1: Synthetic routes to isoxazoles 7a–7e.
  
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3. Scheme 2: Synthetic routes to isoxazoles 7f–7h.
  
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4. Scheme 3: Benzaldehyde photocycloaddition to 7a–7e.
  
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5. Scheme 4: Photochemical ring contraction of isoxazoles 7f–7h.
  
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6. Scheme 5: Photocycloaddition of aromatic aldehydes to di- and trimethyl isoxazoles 7d and 7e.
  
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7. Scheme 6: Preparative photocycloadditions of 7e with aromatic aldehydes.
  
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8. Figure 1: Structures of the photoproducts 9a–9c in the crystal.
  
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9. Scheme 7: T-type photochromism of isoxazole–aldehyde pairs.
  
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10. Scheme 8: Reductive cleavage of the trimethylisoxazole adduct 9a.
  
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Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

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Application of the diastereoselective photodeconjugation of α,β-unsaturated esters to the synthesis of gymnastatin H

Ludovic Raffier and
Olivier Piva

Full Research Paper
Published 02 Feb 2011

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1. Graphical Abstract
2. Scheme 1: Principle of the photodeconjugation process.
  
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3. Scheme 2: Enantio- and diastereoselective photodeconjugation reactions.
  
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4. Figure 1: Natural products prepared by photodeconjugation.
  
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5. Figure 2: Natural amides possessing the same (6R)-fatty acid side chain.
  
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6. Scheme 3: Reagents and conditions: (a) NaH, 13a, THF, 25 °C, 83%. (b) KOH, EtOH/H₂O (95/5), Δ, 97% (E/Z: 90/1...
  
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Beilstein J. Org. Chem. 2011, 7, 151–155, doi:10.3762/bjoc.7.21

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Formation of macrocyclic lactones in the Paternò–Büchi dimerization reaction

Junya Arimura,
Tsutomu Mizuta,
Yoshikazu Hiraga and
Manabu Abe

Letter
Published 28 Feb 2011

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1. Graphical Abstract
2. Scheme 1: Reaction of furan with triplet excited carbonyls, regioselectivity.
  
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3. Scheme 2: Possible pathways for the photochemical reaction of furan derivatives 1a–c.
  
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4. Scheme 3: Synthesis and the photochemical reaction of furan-2-ylmethyl 2-oxoacetates 1a,b.
  
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5. Figure 1: X-ray crystal structure of the macrocyclic lactone 2a.
  
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6. Figure 2: ¹H NMR spectra (500 MHz) for (a) the photolysate of 1a after 4 h irradiation in degassed and dried C...
  
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Beilstein J. Org. Chem. 2011, 7, 265–269, doi:10.3762/bjoc.7.35

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Photoinduced homolytic C–H activation in N-(4-homoadamantyl)phthalimide

Nikola Cindro,
Margareta Horvat,
Kata Mlinarić-Majerski,
Axel G. Griesbeck and
Nikola Basarić

Full Research Paper
Published 02 Mar 2011

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1. Graphical Abstract
2. Scheme 1: Photoinduced domino reaction of adamantylphthalimide.
  
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3. Scheme 2: Synthesis of homoadamantylphthalimide 5.
  
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4. Figure 1: Molecular structure of 5, the geometry optimization was performed by use of DFT B3LYP/6-31G.
  
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5. Scheme 3: Products after irradiation of 5.
  
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6. Scheme 4: Proposed mechanism for the photochemical transformation of 5.
  
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Beilstein J. Org. Chem. 2011, 7, 270–277, doi:10.3762/bjoc.7.36

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Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

Heiko Ihmels and
Jia Luo

Full Research Paper
Published 04 Mar 2011

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1. Graphical Abstract
2. Scheme 1: Photorearrangements of dibenzobarrelenes 1a and 1b.
  
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3. Scheme 2: Stereoselective DPM rearrangement of chiral salts in the solid-state.
  
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4. Scheme 3: Synthesis of ureido- and thioureido-substituted dibenzobarrelene derivatives 1e–i.
  
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5. Scheme 4: Di-π-methane rearrangements of ureido- and thioureido-substituted dibenzobarrelene derivatives 1h a...
  
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6. Figure 1: Photometric titration of A) tetrabutylammonium chloride (TBAC) to 1h (c_1h = 50 µM) and of B) tetrab...
  
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7. Figure 2: Structures of chiral additives employed in DPM rearrangements.
  
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8. Figure 3: Structure of anthracene–thiourea conjugate 4.
  
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9. Figure 4: Proposed structure of the complex between 1h and mandelate SMD.
  
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Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

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Supramolecular FRET photocyclodimerization of anthracenecarboxylate with naphthalene-capped γ-cyclodextrin

Qian Wang,
Cheng Yang,
Gaku Fukuhara,
Tadashi Mori,
Yu Liu and
Yoshihisa Inoue

Full Research Paper
Published 07 Mar 2011

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1. Graphical Abstract
2. Scheme 1: Biphenyl-capped (5), naphthalene-capped (6), and naphthalene-appended γ-cyclodextrin (7).
  
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3. Figure 1: UV–vis spectral changes of 0.2 mM AC upon increasing the concentration of 7 in pH 9 phosphate buffe...
  
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4. Figure 2: Circular dichroism spectra of 7 (0.2 mM) in the presence of 0, 0.0083, 0.025, 0.048, 0.071, 0.093, ...
  
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5. Figure 3: Circular dichroism spectra of 6 (0.2 mM) in the presence of 0, 0.0083, 0.025, 0.048, 0.071, 0.093, ...
  
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6. Figure 4: UV–vis spectra of AC (black dashed line) and 7 (red dashed line) and fluorescence spectra of 7 (0.0...
  
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Beilstein J. Org. Chem. 2011, 7, 290–297, doi:10.3762/bjoc.7.38

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Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan

Axel G. Griesbeck,
Jörg Neudörfl and
Alan de Kiff

Full Research Paper
Published 26 Apr 2011

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1. Graphical Abstract
2. Scheme 1: Three phthalimide/amino acid model reactions: Norrish II process of 1, PET decarboxylation of 3, PE...
  
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3. Figure 1: Phthalimides from tyrosine 8, histidine 9 and tryptophan 10.
  
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4. Scheme 2: PET decarboxylation/photocleavage of 8 and 9.
  
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5. Figure 2: Structure of the tryptophan derivative 10 in the crystal.
  
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6. Figure 3: UV–vis absorption spectra of compounds 8–10 (c = 2 × 10⁻⁴ in CH₃OH).
  
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7. Scheme 3: Direct, triplet-sensitized and ET-sensitized photochemistry of 10.
  
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8. Figure 4: Fluorescence spectra of compounds 8–10 (c = 6 × 10⁻⁵ in CH₃OH).
  
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9. Scheme 4: Mechanistic scenario.
  
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Beilstein J. Org. Chem. 2011, 7, 518–524, doi:10.3762/bjoc.7.60

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The arene–alkene photocycloaddition

Ursula Streit and
Christian G. Bochet

Review
Published 28 Apr 2011

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1. Graphical Abstract
2. Scheme 1: Photochemistry of benzene.
  
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3. Scheme 2: Three distinct modes of photocycloaddition of arenes to alkenes.
  
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4. Scheme 3: Mode selectivity with respect of the free enthalpy of the radical ion pair formation.
  
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5. Scheme 4: Photocycloaddition shows lack of mode selectivity.
  
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6. Scheme 5: Mechanism of the meta photocycloaddition.
  
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7. Scheme 6: Evidence of biradiacal involved in meta photocycloaddition by Reedich and Sheridan.
  
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8. Scheme 7: Regioselectivity with electron withdrawing and electron donating substituents.
  
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9. Scheme 8: Closure of cyclopropyl ring affords regioisomers.
  
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10. Scheme 9: Endo versus exo product in the photocycloaddition of pentene to anisole [33].
  
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11. Scheme 10: Regio- and stereoselectivity in the photocycloaddition of cyclopentene with a protected isoindoline....
  
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12. Scheme 11: 2,6- and 1,3-addition in intramolecular approach.
  
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13. Scheme 12: Linear and angularly fused isomers can be obtained upon intramolecular 1,3-addition.
  
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14. Scheme 13: Synthesis of α-cedrene via diastereoselective meta photocycloaddition.
  
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15. Scheme 14: Asymmetric meta photocycloaddition introduced by chirality of tether at position 2.
  
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16. Scheme 15: Enantioselective meta photocycloaddition in β-cyclodextrin cavity.
  
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17. Scheme 16: Vinylcyclopropane–cyclopentene rearrangement.
  
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18. Scheme 17: Further diversification possibilities of the meta photocycloaddition product.
  
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19. Scheme 18: Double [3 + 2] photocycloaddition reaction affording fenestrane.
  
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20. Scheme 19: Total synthesis of Penifulvin B.
  
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21. Scheme 20: Towards the total synthesis of Lacifodilactone F.
  
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22. Scheme 21: Regioselectivity of ortho photocycloaddition in polarized intermediates.
  
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23. Scheme 22: Exo and endo selectivity in ortho photocycloaddition.
  
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24. Scheme 23: Ortho photocycloaddition of alkanophenones.
  
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25. Scheme 24: Photocycloadditions to naphtalenes usually in an [2 + 2] mode [79].
  
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26. Scheme 25: Ortho photocycloaddition followed by rearrangements.
  
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27. Scheme 26: Stable [2 + 2] photocycloadducts.
  
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28. Scheme 27: Ortho photocycloadditions with alkynes.
  
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29. Scheme 28: Intramolecular ortho photocycloaddition and rearrangement thereof.
  
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30. Scheme 29: Intramolecular ortho photocycloaddition to access propellanes.
  
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31. Scheme 30: Para photocycloaddition with allene.
  
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32. Scheme 31: Photocycloadditions of dianthryls.
  
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33. Scheme 32: Photocycloaddition of enone with benzene.
  
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34. Scheme 33: Intramolecular photocycloaddition affording multicyclic compounds via [4 + 2].
  
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35. Scheme 34: Photocycloaddition described by Sakamoto et al.
  
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36. Scheme 35: Proposed mechanism by Sakamoto et al.
  
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37. Scheme 36: Photocycloaddition described by Jones et al.
  
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38. Scheme 37: Proposed mechanism for the formation of benzoxepine by Jones et al.
  
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39. Scheme 38: Photocycloaddition observed by Griesbeck et al.
  
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40. Scheme 39: Mechanism proposed by Griesbeck et al.
  
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41. Scheme 40: Intramolecular photocycloaddition of allenes to benzaldehydes.
  
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Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

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Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

Henning Hopf,
Vitaly Raev and
Peter G. Jones

Full Research Paper
Published 24 May 2011

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1. Graphical Abstract
2. Scheme 1: [2.2]Paracyclophanes as scaffolds for intraannular photodimerization reactions in solution.
  
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3. Scheme 2: Stereospecific intramolecular [2+2]photoadditions using [2.2]paracyclophane spacers.
  
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4. Scheme 3: Different conformations of pseudo-geminal divinyl[2.2]paracyclophane.
  
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5. Scheme 4: Preparation of tetraene 11.
  
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6. Scheme 5: Photolysis of tetraene 11.
  
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7. Figure 1: The molecule of compound 13 in the crystal. Ellipsoids correspond to 30% probability levels.
  
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8. Scheme 6: Photolysis of trans,trans-dienal 10.
  
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9. Figure 2: The molecule of compound 15 in the crystal. Ellipsoids correspond to 30% probability levels.
  
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10. Scheme 7: Cis–trans-isomerizations of the double bonds of the pseudo-geminal cyclophanes 11 and 19.
  
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11. Scheme 8: Preparation of the vinylcyclopropanes 22–24.
  
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12. Figure 3: The two independent molecules of compound Z,Z-22 in the crystal. Ellipsoids correspond to 50% proba...
  
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13. Figure 4: The molecule of compound 23 in the crystal. Ellipsoids correspond to 50% probability levels.
  
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14. Figure 5: The molecule of compound 24 in the crystal. Ellipsoids correspond to 30% probability levels.
  
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Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

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Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

Wang-Yong Yang,
Samantha A. Marrone,
Nalisha Minors,
Diego A. R. Zorio and
Igor V. Alabugin

Full Research Paper
Published 16 Jun 2011

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1. Graphical Abstract
2. Figure 1: Structure of C-lysine conjugates.
  
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3. Figure 2: Alternative pathways of enediyne photoreactivity: photo-Bergman cyclization (left), C1–C5 cyclizati...
  
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4. Figure 3: Summary of possible mechanistic alternatives for the observed DNA cleavage by monoacetylene conjuga...
  
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5. Scheme 1: Proposed mechanism of photocycloaddition of acetylene with 1,4-CHD.
  
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6. Figure 4: p-, m-, and o-amidyl acetylenes and respective lysine conjugates.
  
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7. Scheme 2: Synthesis of amido-substituted monoacetylenes and lysine conjugates. Reagents and conditions: a. Pd...
  
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8. Scheme 3: Photochemical reactions of TFP-substituted aryl alkynes with selected π-systems. In short, the reac...
  
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9. Scheme 4: Photocycloaddition of amido acetylenes with 1,4-CHD.
  
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10. Scheme 5: Possible mechanism for photochemical hydration of diaryl acetylene moiety catalyzed by the ortho-am...
  
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11. Figure 5: Stern–Volmer plots of three regioisomers, 3 (blue diamond), 4 (red square), and 5 (green triangle),...
  
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12. Figure 6: Absorption spectra of three isomers, 3, 4, 5, and Ph-TFP in acetonitrile (10 μM).
  
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13. Figure 7: Quantified DNA cleavage data for 1 (a), 6 (b) and 7 (c). Blue: Form I (supercoiled) DNA; red: Form ...
  
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14. Figure 8: Effect of hydroxyl radical/singlet oxygen scavengers (20 mM) on the efficiency of DNA cleavage at p...
  
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15. Figure 9: Cell proliferation assay using A375 cells (human melanoma) and compound 1 (green square), 6 (red up...
  
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Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

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