Synthesis of 2‐Azulenyl‐1,1,4,4‐tetracyano‐3‐ferrocenyl‐1,3‐butadienes by [2+2] Cycloaddition of (Ferrocenylethynyl)azulenes with Tetracyanoethylene

Abstract

1-, 2-, and 6-(Ferrocenylethynyl)azulene derivatives 10-16 have been prepared by palladium-catalyzed alkynylation of ethynylferrocene with the corresponding haloazulenes under Sonogashira-Hagihara conditions. Compounds 10-16 reacted with tetracyanoethylene (TCNE) in a [2+2] cycloaddition-cycloreversion reaction to afford the corresponding 2-azulenyl-1,1,4,4,-tetracyano-3-ferrocenyl-1,3-butadiene chromophores 17-23 in excellent yields. The redox behavior of the novel azulene chromophores 17-23 was examined by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions.

Synthesis and Properties of Azulene‐Substituted Donor–Acceptor Chromophores Connected by Arylamine Cores

“…However, most such reagents are toxic or expensive, and/or the reaction with the reagents often requires harsh reaction conditions 12–14. We have recently developed an efficient iodination procedure using NaI in the presence of N ‐chlorosuccinimide (NCS) 8e,9a,15. Thus, we have examined the preparation of iodoarylamines 5 – 8 starting from arylamines 1 – 4 ; iodination of 1 – 4 requires that the next reaction be palladium‐catalyzed cross‐coupling reaction.…”

Azulene‐Based Donor–Acceptor Systems: Synthesis, Optical, and Electrochemical Properties

“…Preparation of ferrocene-substituted AzTCBDs 40-46 was accomplished by the [2+ +2] CA-RE of ferrocenylethynylazulene derivatives with TCNE ( Figure 8). [54] In this reaction, the ferrocenes ubstituent on 2and 6-ethynylazulenes acts as an activating group and accelerates the [2+ +2] CA-RE reaction.…”

Reactions of Alkynyl‐ and 1,1′‐Dialkynylferrocenes with Tetracyanoethylene – Unanticipated Addition at the Less Electron‐Rich of Two Triple Bonds

“…[19] Bruce et al, who used metal acetylide substituted ferrocenes as substrates, have explored this chemistry in depth. [25][26][27][28][29][30][31][32] Very recently, related reactions of diferrocenyl substrates have been reported. [25][26][27][28][29][30][31][32] Very recently, related reactions of diferrocenyl substrates have been reported.…”