MP2 and DFT Calculations on Circulenes and an Attempt to Prepare the Second Lowest Benzolog, [4]Circulene

✍ Scribed by Hilmar Christoph; Jörg Grunenberg; Henning Hopf; Ina Dix; Peter G. Jones; Martin Scholtissek; Günther Maier

• Book ID: 102796574
• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 927 KB
• Volume: 14
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200701837

✦ Synopsis

Abstract

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 dithiol 23, 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.