- NMR and DFT study on onium ions derived from substituted fluoranthenes and benzo[κ]fluoranthenes
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Fluoranthene and benzo[k]fluoranthene (3) are nonalternant polyaromatic hydrocarbons. Their derivatives, 3-acetyl, 8-acetyl, 3-nitro, and 3-aminofluoranthenes (4, 5, 7, and 8) were reacted in FSO3H/SO 2ClF and the solutions were observed by NMR measurements at low temperatures, which showed the formation of PAH-substituted onium ions. The most deshielded 13C peaks in fluoranthene frames were observed at 155.7 and 148.7 ppm for 4H+, 154.4 ppm for 5H+, 159.1 and 139.6 ppm for 7H+, and 139.7 ppm for 8H+. Distribution of the positive charges were estimated on the basis of changes in 13CNMR chemical shifts between onium ions and their corresponding parent compounds. Only limited delocalization of positive charges into the aromatic rings was found to occur. GIAO-derived NMR chemical shifts calculated by the DFT method were generally consistent with the experimental chemical shifts. DFT calculations suggested that benzo[k]fluoranthene (3) is favored to be protonated at C-3/C-7 positions. GIAO-derived NICS(1)zz were computed to elucidate aromaticity/antiaromaticity, and the results suggested that the five-membered rings are antiaromatic for cations 4H+, 7H+, 8H +, and 3aH+ (3-benzo[k]fluoranthenium ion).
- Okazaki, Takao,Adachi, Taisuke,Kitagawa, Toshikazu
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- Photochemical approach to new polycyclic substrates suitable for further photocatalytic functionalization
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New polycyclic compounds are synthesized by photocycloaddition reactions of methoxy, methyl or phenyl substituted butadiene derivatives 11-14. Mono- and dimethoxy butadiene derivatives 11 and 12 undergo intramolecular [2+2] photocycloaddition giving benzobicyclo[3.2.1]octadiene structures (endo-15, endo,trans-17) as main products. As minor photoproducts tricyclic compounds endo-16 and endo,trans-18 are isolated, respectively, formed by [4+2] photoinduced cycloaddition of the starting molecules. The reaction of compounds 13 and 14 is more selective and only benzobicyclo[3.2.1]octadienes endo,endo-19 and endo,endo-20 are formed, respectively. New bicyclo[3.2.1]octadienes with isolated double bond can be suitable substrates for further efficient photocatalytic oxygenations in course of new functionalized polycycles, potentially new biologically active compounds.
- Vuk, Dragana,kori, Irena,Marini, eljko
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- Thermal electrocyclization reactions II: Benzooctatetraenes and benzodecapentaenes
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Thermal electrocyclization reactions of benzooctatetraenes and benzodecapentaenes substituted with R=H, Cl, and methyl were studied experimentally and computationally. Methyl and unsubstituted benzooctatetraenes and benzodecapentaenes give the [4.2.0]bicyclooctadiene products by 8π,6π-electrocyclization. Chlorine substitution led to thermal rearrangement of the initially formed 8π,6π-electrocyclization intermediates to give unprecedented products.
- Vuk, Dragana,Marini?, ?eljko,Mol?anov, Kre?imir,Margeti?, Davor,?kori?, Irena
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p. 886 - 891
(2014/01/23)
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- Weak interactions direct crystal packings of arylated 1,3-butadienes
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Four novel aryl butadienes (substituted with R = Cl, OCH3, NO2 and H) were prepared and characterised by X-ray diffraction, IR, UV/Vis and NMR spectroscopies. A comparative analysis of crystal packings was aimed to determining influence of weak interactions: CHa?O and CHa?Cl hydrogen bonds, CHa?π interactions and dispersion interactions. Since no proton donors is present and since the molecules are sterically very similar, these weak interactions are responsible for wide variation in 3D packing and supramolecular motives.
- Vuk, Dragana,Mol?anov, Kre?imir,?kori?, Irena
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- Photochemical transformation of β,β′-dithienyl substituted o-divinylbenzenes leading to 1,2-dihydronaphthalenes or fused pentacyclic compounds: First evidence of electrocyclization process via 2,3- dihydronaphthalene intermediates
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The photochemical behaviour of 2,2′-(o-phenylenedivinylene) dithiophenes (7a-c), 3,3′-(o-phenylenedivinylene)dithiophene (8a) and 3,3′-(o-phenylenedivinylene)dibenzothiophene (8b) was studied under the low concentrations. An intramolecular reaction via the 2,3-dihydronaphthalene intermediate has been observed in all studied examples accompanied by dimerization and polymerization. The 1,2-dihydro-2,3-dithienylnaphthalenes (9a-c) were isolated (7-9%) from the 2-thiophene derivatives while the 3-thiophene derivatives gave polycyclic structures (13-44% yield).
- Vuk, Dragana,Marini?, ?eljko,Mol?anov, Kre?imir,Koji?-Prodi?, Biserka,?indler-Kulyk, Marija
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p. 6873 - 6880
(2012/09/22)
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- Aromatic ylide-stabilized carbocyclic silylene
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New ring on the block: A new type of silylene (see scheme) has been synthesized and is stabilized by the ylidic carbon centers which serve as π-donor substituents while attenuating the σ-withdrawing effects of the nitrogen groups. The electronic and structural features of this neutral silaaromatic system were probed using DFT calculations. Copyright
- Asay, Matthew,Inoue, Shigeyoshi,Driess, Matthias
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supporting information; experimental part
p. 9589 - 9592
(2011/12/05)
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