title: The chemistry of four-membered aromatics.
abstract: This article provides an overview on the aromatic systems of four-membered rings. These aromatic four-membered ring systems are rather exotic because of a poor correspondence between the Hückel rule and the structure of four-membered rings. Consequently, such aromatics are generally dications or dianions, to form 2π or 6π electron systems respectively. Alternatively, the use of open-shell structures or empty d-orbitals of transition metal atoms could give neutral aromatic four-membered ring systems. This paper summarizes the four-membered aromatic compounds reported to date and describes the various methods for evaluating their aromaticity.
authors: Department of Chemistry, School of Science, The University of Tokyo, Hongo, Tokyo 113-0033, Japan. matsuo@chem.s.u-tokyo.ac.jp
authors: Yutaka
authors: Y
authors: Matsuo
authors: Masashi
authors: M
authors: Maruyama