Derivate der Ketipinsäure, II. Ketipinsäuredilacton und verwandte Verbindungen

Abstract

Derivatives of Ketipic Acid, II. – Ketipic Acid Dilactone and Related Compounds The highly reactive title compound 7 was prepared by thermal decomposition of the disguised oxalylbisketene 6 . Ring opening of 7 with nucleophiles leads to γ‐alkylidenetetronic acids 4 . α‐Substituted derivatives of 4a give rise to unsymmetrical dilactones 9a–c and the dibromodilactone 9d . The alkylidenetetronic acids are stabilized in the E configuration by hydrogen bridges. The pairs of isomeric ( E )‐ and ( Z )‐alkylidenetetronic acids 3 and 4 show characteristic spectral differences.