Ring-chain transformation reactions of heterocycles have been proven to be a powerful tool for the synthesis of a wide range of carbocyclic as well as heterocyclic compounds.1 View all references The ring transformation reactions of pyryliums and thiopyryliums have been known for a long time.[2]5. Dolling , W. and Schroth , W. 1992. Houben-Weyl Edited by: Kreher , RP Vol. E 7b/2, P687Stuttgart: Thieme. ... View all references Many reactions about this method ...