Systems With a Spirocyclic Heteroatom

Abstract This article covers an overview of synthesis and reactivity of azoniaspiro compounds. The spirocyclic ammonium derivatives contain a nitrogen atom at the point of fusion. These quaternary compounds are isolated and characterized as salts. A brief update on experimental and structural methods of azoniaspiro salts is given. Theoretical concepts and thermodynamic aspects are illustrated. The synthesis of all types of azoniaspiro derivatives is described, which includes recent examples of different ring formation. Finally, the importance of these compounds and their broad spectrum of applications are presented.