Tricyclic Quinazoline Alkaloids Conjugated to Ferrocene: Synthesis, Structure, and Redox Behavior of Ferrocenylmethylene‐Substituted 7H‐Deoxyvasicinones

Abstract

AbstractThe first organometallic derivatives of tricyclic quinazoline derivatives are prepared by condensation of the active C‐3 methylene group of 7H‐deoxyvasicinones with ferrocenecarbaldehyde. By following this route the conjugated parent alkaloid and derivatives with nitro, amino, as well as some alkanoylamino groups at C‐7 were attached at the ferrocene moiety, thereby significantly extending the π system. In addition, the parent compound was subjected to the reaction by treatment with ferrocene‐1,1′‐dicarbaldehyde, giving rise to the double condensation product, which is only the second case of a 1,1′‐disubstituted ferrocene derivative with two alkaloid substituents. A number of the compounds obtained were subjected to X‐ray crystallographic analyses. In all cases, the substituents adopt a coplanar conformation with the ferrocene cyclopentadienyl ligands. The influence of the substituents at C‐7 through the extended conjugated π system on the iron atom is reflected by results of cyclic voltammetric measurements as well as by DFT calculations.