Abstract
Mohamed Abdel-Megid
Most of the common and novel synthesized active methylene compounds as well as heterocycles bearing active methyl or having methine site were used in the syntheses of wide variety of five-, six- and seven-membered azaheterocyclic systems having oxygen or sulfur atom in their structures in addition to some oxygenated heterocycles such as pyrans. Many synthetic approaches were used for the preparation of target heterocyclic systems such as cyclocondensation reactions, ring opening-ring closure, cycloaddition, acid-, base-catalyzed reaction, intermolecular cyclization and self-condensation as well as ring–chain tautomerism has been reviewed in this paper.
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