Chemistry of Hetero Analogs of Pentalene Dianion

Abstract

This chapter is devoted to recent progress in the chemistry of the 5:5 fused heterocyclic systems. There are four possible modes of 5:5 fusions of the simple five-membered heterocycles leading to four structures containing one het-eroatom in each ring. The heteroatoms may be the same or different and may be O, NH, S, Se, Te, P, As, or Sb. The fully conjugated hetero analogs of pentalene dianion have a central CC bond and are isoelectronic with the 10-π-electron pentalene dianion. The scope of the chapter is outlined with a survey of various structural types and nomenclature of the parent compounds and their derivatives. New synthetic procedures and synthetic applications of title compounds are presented. This review has concentrated on the new developments achieved from 1997 to September 2007.