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Volume 11: Five-Membered Hetarenes with One Chalcogen and One Additional Heteroatom |
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Introduction by Prof. Ernst Schaumann (Volume Editor): |
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This volume is the third in Hetarenes and Related Ring Systems (Category 2) of Science of Synthesis and deal with five-membered hetarenes with one chalcogen and one additional heteroatom. Throughout this category, a hetarene is considered to be a heterocyclic ring with a fully conjugated perimeter of π- or nonbonding electrons. Also, potentially tautomeric systems with a hydroxy, sulfanyl, or amino substituent are included when conjugation is possible at least in one tautomer. In the present volume, this formal definition leads to quite different types of five-membered heterocyclic ring systems including the 1,2- or 1,3-arrangement of two chalcogen atoms to give cationic rings, as well as 1,2- or 1,3-combinations of a chalcogen atom and a nitrogen or phosphorus atom. The latter group comprises well-known ring systems such as oxazoles or thiazoles, but also less well-studied ring systems.
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In each case, not only monocyclic rings are considered but also annulated derivatives,in particular benzoannulated systems, and other examples of arenoannulationand also hetarenoannulation. When convenient, syntheses of these derivatives are covered together with the chemistry of the monocycles, otherwise they immediately follow the chapter on the corresponding monocyclic system. A separate chapter is devoted to the chemistry of tri- or tetraheterapentalenes, which have a particularly interesting electronic structure.
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