- Perchlorotriphenylene: A Compound with Severe Molecular Twisting?
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Perchlorotriphenylene has been reported several times in the literature.However, there is inconclusive evidence that this compound has actually been prepared.Severe molecular twisting to relieve steric interactions of "ortho" chlorines may preclude any stable existence.The compound is discussed in context with other severely twisted molecules, and methods are proposed for its synthesis.
- Campbell, M. C.,Humphries, R. E.,Munn, N. M.
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- Access to polysubstituted naphthalenes and anthracenes via a retro-Diels–Alder reaction
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Naphthalene and anthracene nuclei are present in several natural and synthetic compounds. Due to their unique physical and chemical properties, access to functionalized naphthalenes and anthracenes has attracted the attention of both synthetic and medicinal chemists over the decades. In this study, successive Diels–Alder/retro-Diels–Alder reactions of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate with various bicyclic alkenes in one pot to yield naphthalene and anthracene derivatives are reported. Using anti- and syn-cyclotrimers derived from the cyclotrimerization of benzobarrelene as alkene partner enabled efficient synthesis of trinaphthylene.
- Akin, Esra Turan,Erdogan, Musa,Dastan, Arif,Saracoglu, Nurullah
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supporting information
p. 5537 - 5546
(2017/08/22)
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- Natural formation of chlorinated phenols, dibenzo-p-dioxins, and dibenzofurans in soil of a Douglas fir forest
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The natural formation of 4-MCP, 24/25- and 26-DCP, and 245-TrCP was detected in four selected areas of a rural Douglas fir forest where the humic layer was spiked in situ with a solution of Na37Cl and covered by an enclosure, after 1 year of incubation. Chlorinated phenols (CP) can be formed naturally from organic matter and inorganic chloride by either de novo synthesis or chloroperoxidase (CPO)-catalyzed chlorination. The natural CP congeners were found to be present in high concentrations in soil compared to the other congeners, except for 245-TrCP which was present in a relatively low concentration. This study did not reveal which source, natural or anthropogenic, caused the observed concentrations. Some 20 chlorinated dibenzo-p-dioxins and dibenzofurans (CDD/F) were found to be formed naturally in soil of the Douglas fir forest; the formation of three 2,3,7,8-substituted congeners, 2378-TeCDD, 12378-PeCDD, and 123789-HxCDD, deserves special attention. A formation mechanism has been proposed which starts from naturally formed CP congeners and which probably involves peroxidase mediation. Chlorination of CDD/F congeners by the CPO-mediated reaction cannot be ruled out, but seems to be less likely due to the absence of several predicted congeners. The natural formation of 4-MCP, 24/25- and 26-DCP, and 245-TrCP was detected in four selected areas of a rural Douglas fir forest where the humic layer was spiked in situ with a solution of Na37Cl and covered by an enclosure, after 1 year of incubation. Chlorinated phenols (CP) can be formed naturally from organic matter and inorganic chloride by either de novo synthesis or chloroperoxidase (CPO)-catalyzed chlorination. The natural CP congeners were found to be present in high concentrations in soil compared to the other congeners, except for 245-TrCP which was present in a relatively low concentration. This study did not reveal which source, natural or anthropogenic, caused the observed concentrations. Some 20 chlorinated dibenzo-p-dioxins and dibenzofurans (CDD/F) were found to be formed naturally in soil of the Douglas fir forest; the formation of three 2,3,7,8-substituted congeners, 2378-TeCDD, 12378-PeCDD, and 123789-HxCDD, deserves special attention. A formation mechanism has been proposed which starts from naturally formed CP congeners and which probably involves peroxidase mediation. Chlorination of CDD/F congeners by the CPO-mediated reaction cannot be ruled out, but seems to be less likely due to the absence of several predicted congeners.
- Hoekstra, Eddo J.,De Weerd, Henk,De Leer, Ed W. B.,Brinkman, Udo A.Th.
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p. 2543 - 2549
(2007/10/03)
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- De novo synthesis mechanism of polychlorinated dibenzofurans from polycyclic aromatic hydrocarbons and the characteristic isomers of polychlorinated naphthalenes
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Polychlorinated dibenzofurans (PCDFs) and polychlorinated naphthalenes (PCNs) are known to be emitted from municipal waste incinerators (MWIs) with polychlorinated dibenzo-p-dioxins (PCDDs). Two formation paths for PCDD/Fs could mainly work, which are condensation of the precursors such as chlorophenols and 'de novo' formation from carbon. However the correlation between the chemical structure of carbon and the resulting PCDD/Fs still remains unknown. In this study, the PCDD/Fs formation from polycyclic aromatic hydrocarbons (PAHs) and CuCl was examined at 400 under 10% O2. Coronene among the PAHs characteristically gave 1,2,8,9-T4CDF and the derivatives. These isomers clearly indicate that chlorination causes the cleavage of the C-C bonds in a coronene molecule and also that oxygen is easily incorporated from its outside to form 1,2,8,9-T4CDF. The symmetrical preformed structures in the coronene molecule enabled to amplify the de novo formation of the isomer. PCNs are also formed directly from these PAHs. Since there have been few reports on the formation mechanism of PCNs, this study will be a first step to know the whole formation paths. We also define the de novo synthesis as the breakdown reaction of a carbon matrix, since the word has been used without the precise definition.
- Iino,Imagawa,Takeuchi,Sadakata
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p. 1038 - 1043
(2007/10/03)
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- Regiospecific fragmentation of benzene derivatives: Synthetic and analytical applications
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The cycloadducts formed from arenes and tetrachloro- and tetrafluorobenzyne have been shown to undergo specific addition-fragmentation reactions. These sequences are both simple syntheses of arenes with unusual substitution patterns and a convenient alternative to the other methods currently available for assaying the isotopic distribution in [14C]-labelled benzene derivatives.
- Hales, Neil J.,Heaney, Harry,Hollinshead, John H.,Ley, Steven V.
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p. 7755 - 7776
(2007/10/02)
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- The synthesis and assay of radiolabelled benzene derivatives
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Several new syntheses of 1- and 4-[14C]anisole have been investigated and routes from [14C]cyanide and from 2-[14C]acetone are described which are better than those previously reported. The key step in one of the syntheses was catalytic dehydrogenation of 1-[14C]cyclohexanone to 1-[14C]phenol. Degradation of 5,6,7,8-tetrachloro-3,4-dihydro-1,4-etheno-[14C]naphthalen-2-(1H)-on e (10) prepared from [14C]anisole and tetrachlorobenzene has shown that the key step had proceeded without scrambling of the label.
- Hales, Neil J.,Heaney, Harry,Hollinshead, John H.,Ley, Steven V.
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p. 7741 - 7754
(2007/10/02)
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- PREPARATION OF NAPHTHALENE DERIVATIVES BY REACTION OF BENZYNES WITH TIOPHENE-1,1-DIOXIDES
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The reaction of benzynes with thiophene-1,1-dioxides afford the Diels-Alder cycloadducts which spontaneously lose sulphur dioxide to give the corresponding naphthalene derivatives in moderate yields.Further reaction of benzyne with naphthalenes yielding dibenzobarrelenes is observed in a few cases.
- Nakayama, Juzo,Kuroda, Masami,Hoshino, Masamatsu
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p. 1233 - 1236
(2007/10/02)
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- A Contribution to the Bisnorcaradiene Problem. Synthesis, Properties, and Structural Parameters of Bicycloundecapentaene - the Valence Isomer of Bisnorcaradiene
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The problem of the existence of bisnorcaradiene (2) is discussed.MINDO/3 calculations show that the equilibrium of 2 (bearing substituents) with its valence isomers 5 and 21 is shifted towards 5 and 21 with about 11 kcal/mol.The photolysis of the spironorcaradiene/spirotropylidene equilibrium mixtures (78) followed by NMR-spectroscopy allowed the detection of the valence isomer 5.Irradiations of (78) on a preparative scale gave mixtures of hydrocarbons 5, 16, 17, 18, 19, and 20.In the case of the dibenzo derivative, the bicycloundecapentaene 5e could be isolated.NMR and CMR spectra as well as an X-ray analysis clearly established the structure to be 5e.Even at low temperature the bisnorcaradiene (2) could not be detected by NMR spectroscopy.Thermolysis of 5a - e giving 16 and 17 can be explained via an equilibrium 5221, i.e. a bisnorcaradiene must be involved as an unstable intermediate.The photorearrangement of (78) producing 5 (221) has most probably to be regarded as a di-?-methane rearrangement.
- Duerr, Heinz,Pauly, Karl-Heinz,Fischer, Karl
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p. 2855 - 2871
(2007/10/02)
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