63548-78-7Relevant academic research and scientific papers
MP2 and DFT calculations on circulenes and an attempt to prepare the second lowest benzolog, [4]circulene
Christoph, Hilmar,Grunenberg, Joerg,Hopf, Henning,Dix, Ina,Jones, Peter G.,Scholtissek, Martin,Maier, Guenther
, p. 5604 - 5616 (2008)
MP2 and DFT calculations have been carried out for [n]circulenes for n=3 to 20 in order to predict the strain energy and topology of these cyclically condensed aromatic systems. To synthesise [4]circulene (2), 1,5,7,8- tetrakis(bromomethyl)biphenylene (14) was prepared from the corresponding tetramethyl derivative (8) and subjected to various dehalogenation reactions; all attempts to obtain [2.2]biphenylenophane (7) as a precursor for 2 by this route failed. Treatment of 14 with sodium sulfide furnished the thiaphanes 16 and 17, thermal and photochemical desulfurization of which also failed to provide 7. In a second approach [2.2]paracyclophane was converted to the pseudo-geminal dithiol23, which was subsequently bridged to the thiaphanes 22 and 24. On flash vacuum pyrolysis at 800°C these were converted exclusively into phenanthrene (30). An approach to dehydrochlorinate the commercial product PARYLENE C to the tetrahydro[4]-circulene 7 led only to polymerisation. The X-ray structures of the intermediates 8, 14, 17, 23, 24, 26, and 35 are reported.
Electron Spin Resonance Spectroscopy of Radical Cations and Anions of Methylated Biphenylenes, Tetraphenylene, and Octa-β-methyltetraphenylene
Avila, David V.,Davies, Alwyn G.,Girbal, Maria L.,Ng, Kai M.
, p. 1693 - 1699 (2007/10/02)
Octa-β-methyltetraphenylene has been prepared in low yield by the thermolysis of tetra-β-methylbiphenylene.The radical cations and radical anions of tetra-α-methylbiphenylene, tetra-β-methylbiphenylene, and octamethylbiphenylene, and the radical cation of octa-β-methyltetraphenylene have been generated and their ESR spectra have been recorded and analysed.In trifluoroacetic acid containing mercury(II) trifluoroacetate, the tetra-α-methylbiphenylene radical cation undergoes mono- and dimercuriation.Tetra-β-methylbiphenylene in tetrahydrofuran in the presence of lithium apparently undergoes ringopening to give a radical anion derived from 2,2'-dilithiobiphenyl.The structures which these spectra imply, particularly the apparent distortion which has been reported in the tetraphenylene radical anion, are discussed.
Cyclooctannelated Biphenylenes. Diagnosis of an Anomalous Bond Length by Analysis of Ring Current Geometric Factors
Wilcox, Charles F.,Farley, Eric N.
, p. 351 - 356 (2007/10/02)
The syntheses and properties of the benzocyclobutene- and naphthocyclobutene-fused dicyclooctabiphenylenes 8 and 9 are described.These ? systems show paratropic 1H NMR effects with magnitudes between those of the parent hydrocarbon dicyclooctabiphenylene (7) and the cyclooctabiphenylenes 1,2,and 3.A complete 1H NMR spectral analysis was performed on a series of 14 polycyclic hydrocarbons related to biphenylene (10) including 1-3 and 7-9.A self-consistent Heuckel-McWeeny ring current model provided an excellent description of the 1H NMR spectra observed for these polycycles.Correlation of biphenylenic 1H NMR chemical shifts with calculated ring currents for the polycycles 1,2,3,7,8,9, and 10 afforded a semiempirical determination of ring current geometric factors for these systems.Deviations of certain observed geometric factors from theoretical "Biot-Savart" values were found to be diagnostic for an unusually long bond in the cyclobutene ring of the higher annelates 2,3,8, and 9.
Dicyclooctabiphenylene. Synthesis and Properties
Wilcox, Charles F.,Farley, Erik N.
, p. 7195 - 7200 (2007/10/02)
The synthesis and properties of the "antiaromatic" hydrocarbon dicyclooctabiphenylene (1) are described.The observed electronic and 1H NMR spectra of 1 agree well with previous predictions.The series of polycycles consisting o
