Electrocyclization of α,β,γ,δ-unsaturated ferrocenyl aldehydes: Synthesis of novel ferrocenyl phenyl decorated pyridines

In this study, we have explored the formation of ferrocenyl-substituted pyridines by utilizing an electrocyclization process with alpha,beta,gamma,delta-unsaturated aldehydes and aqueous ammonia solutions. The reactions occur under solvent-free conditions, although, if needed, water can be used as a solvent; it is a convenient and effective technique, yielding the desired product in just 6 hours. The protocol demonstrates promising results with all the variants of alpha,beta,gamma,delta-unsaturated aldehydes consisting of ferrocenyl, phenyl and acrylates derivatives. All the newly synthesised ferrocenyl pyridine derivatives were fully characterized by the spectroscopic analysis, moreover, molecular structure of 2-(Naphthalene-2-yl)-4-ferrocenyl pyridine (3g) was established by the Single Crystal Xray Diffraction analysis. Some of the ferrocenyl-substituted pyridines were also studied by UV-vis absorption spectroscopy and electrochemical analyses, a comparative study about the effect of electron donating and withdrawing groups has also been discussed.