1 Administration, Department of Chemistry, Faculty of Science, Københavns Universitet2 Department of Chemistry, Faculty of Science, Københavns Universitet3 Department of Chemistry, University of Copenhagen4 Bohdan Khmelnytsky National University5 Department of Chemistry, Faculty of Science, Københavns Universitet6 Administration, Department of Chemistry, Faculty of Science, Københavns Universitet
planar antiaromatic cyclooctatetraenes
In this paper we describe a new class of antiaromatic planar cyclooctatetraenes: the diazadioxacirculenes. The synthesis was achieved by means of a new acid-mediated oxidative dimerization of 3,6-dihydroxycarbazoles to yield the diazadioxacirculenes in high yields. The synthetic protocol appears to be general, and is a one-pot transformation in which two CC bonds and two CO bonds are formed with the loss of two molecules of water. We also present a detailed characterization of the optical and electrochemical properties of this new class of stable planar cyclooctatetraenes. The properties of the diazadioxacirculenes are compared with the properties of isoelectronic tetraoxacirculenes and azatrioxacirculenes. We discuss the antiaromatic nature of the planar central cyclooctatetraene moiety. The antiaromatic nature of the planar cyclooctatetraenes was studied by using computational methods (NICS calculations), and these calculations reveal that the central eight-membered ring has antiaromatic character.
Chemistry: a European Journal, 2013, Vol 19, Issue 50, p. 17097-17102