Novel π‐Extended Quinazoline‐Ferrocene Conjugates: Synthesis, Structure, and Redox Behavior

Abstract

Novel ferrocene conjugates of tricyclic quinazoline derivatives are prepared by condensation of active C‐6 methylene groups of mackinazolinones with ferrocenecarbaldehyde. Following this route the conjugated parent alkaloid as well as derivatives with nitro, amino, and alkanoylamino groups at C‐2 were attached at the ferrocene moiety, thereby significantly extending the delocalized π system. In addition, the parent compound was subjected to the reaction with ferrocene‐1,1'‐dicarbaldehyde, giving rise to the symmetrical and unsymmetrical double condensation products – 1,1'‐disubstituted ferrocene derivatives, which bear two alkaloid substituents. Some of the compounds obtained were subjected to X‐ray crystallographic analyses. The influence of the substituents at C‐2 through the extended conjugated π system on the iron atom is reflected by results of cyclovoltammetric measurements.

The First Anionic Thia‐Fries Rearrangement at the Cobaltocenium Cation

“…[9,10] We have investigated the chemistry of ferrocene under a variety of aspects for a longer period of time. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Among these, the first anionic thia-Fries rearrangements at ferrocene were reported, which start from ferrocenyl triflate (1) or from 1,1'ferrocenediyl ditriflate (3) and gave rearranged products 2 or 4, respectively in high yields under very mild reaction conditions (Scheme 1). [24] Remarkably, 4 was exclusively formed as the meso diastereomer, an unprecedented interannular stereoinduction, which was recently investigated by theoretical calculations.…”

“…We have investigated the chemistry of ferrocene under a variety of aspects for a longer period of time [11–25] . Among these, the first anionic thia‐Fries rearrangements at ferrocene were reported, which start from ferrocenyl triflate ( 1 ) or from 1,1’‐ferrocenediyl ditriflate ( 3 ) and gave rearranged products 2 or 4 , respectively in high yields under very mild reaction conditions (Scheme 1).…”