Bicyclic 5-6 Systems: Two Heteroatoms 1:1

Abstract

This chapter covers bicyclic ring systems that consist of a five- and a six-membered ring with each ring containing one heteroatom that is not situated at a ring junction position. Nine heterocyclic ring systems containing nitrogen, oxygen, and sulfur heteroatoms are covered, including pyrrolopyridines, furopyridines, thienopyridines, pyranopyrroles, thiopyranopyrroles, furopyrans, thienopyrans, thiopyranofurans, and thienothiopyrans. Pyrrolopyridines, furopyridines, thienopyridines, and their pyridinone derivatives have been most widely covered in the chemical literature. For a few of the ring systems, such as thiopyranofurans and thienothiopyrans, there are only scarce references in the literature. In addition to the fully conjugated ring systems, partially and fully reduced derivatives of these compounds are considered. Representative melting point, spectroscopic, and X-ray crystallographic data are presented. Reactivity of the parent and reduced derivatives of the heterocyclic ring systems are provided. Syntheses of the ring systems from acyclic precursors, five- or six-membered ring starting materials, or transformations of other rings are included. A variety of applications of these heterocyclic ring systems are given. A few of the ring systems are found in naturally occuring compounds; however, many of the compounds are only available synthetically.