ABSTRACT SYNTHESIS OF FERROCENYL QUINONES AND POLYQUINANES Eralp, Tug&ccedil / e M.S., Department of Chemistry Supervisor: Assoc. Prof. Dr. Metin Zora June 2005, 79 pages With the discovery of antitumor activity of ferrocene derivatives, research on new ferrocene derivatives have gained importance. For this purpose, we have investigated the synthesis of ferrocenyl quinones starting from squaric acid. Several quinone derivatives are known to have antitumor and antibiotic activities. In this research, by combining ferrocene and quinone moieties, we have targeted ferrocenyl quinones which are supposed to have enhanced potential antitumor activity. Thermolysis of ferrocenyl-substituted 4-alkynyl cyclobutenones, which have been prepared from ferrocenyl cyclobutenediones and alkynyllithiums, leads to the formation of ferrocenyl quinones and besides also cyclopentendiones are observed. Ferrocenyl cyclobutenediones have been prepared from known cyclobutenediones by nucleophilic addition of ferrocenyllithium followed by hydrolysis. A mechanism for the formation of ferrocenyl substituted quinones, involving first electrocyclic ring opening of alkynyl substituted cyclobutenone to ketene intermediate and then ring closure, has been proposed. Polyquinanes are widely found in nature and proved to have biological activity such as antibiotic activity. For the synthesis of ferrocenyl polyquinanes, starting from squaric acid, ferrocenyl substituted cyclobutenediones were prepared and reacted with alkenyllithium, and hydrolyzed to afford ferrocenyl substituted polyquinanes. A mechanism has been proposed that involves first the formation of cis- and trans-divinyl substituted cyclobutenes that produce cyclooctatriene-dienolate, upon hydrolysis of this dienolate, aldol-type transannular ring closure reaction takes place, producing polyquinanes.

This work deals with the enantioselective synthesis of chiral cyclohexenones from substituted 4-nitroisoxazoles and α-bromo-α,β-unsaturated aldehydes using of N-heterocyclic carbenes (NHC) as organocatalysts. The work includes the preparation of commercially unavailable NHC-precursors and the synthesis of starting materials, substituted 4-nitroisoxazoles and α-bromo-α,β-unsaturated aldehydes. The second part of the work deals with the optimization of reaction conditions of the enantioselective synthesis of chiral cyclohexenones, proceeding via an azolium dienolate intermediate, and the detailed substrate scope screening.