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Published on: August 22, 2018
Synthesis of 11H-Indeno[2,1-a]azulenes and Transformation into Azulene-Fused Dicyanobenzofulvenes
Masayuki Iwabuchi1, Miku Yoshida1, Daichi Ando2
1Department of Chemical Biology and Applied Chemistry, College of Engineering, Nihon University, Koriyama 963-8642, Japan.
Abstract:
11H-Indeno[2,1-a]azulenes were efficiently synthesized via the [8 + 2] cycloaddition of 2H-cyclohepta[b]furan-2-ones with the enamines generated from several 1-indanones. Subsequent transformations included halogenation, cross-coupling, oxidation, and/or Knoevenagel condensation to furnish the azulene-fused dicyanobenzofulvenes (DBFs). Comprehensive characterization was accomplished through single-crystal X-ray analysis, UV/vis absorption, fluorescence spectroscopy, and electrochemical methods. The DBFs exhibited pronounced absorption in the visible region, attributed to their donor-acceptor structures. Furthermore, notable halochromic behavior and fluorescence were observed in acidic media for 11H-indeno[2,1-a]azulenes, while the DBFs demonstrated distinct electrochromic properties with reversible spectral changes under the electrochemical redox conditions. Computational nucleus-independent chemical shift (NICS) calculations suggested weak antiaromaticity in the dicyanofulvene moiety of the DBFs.
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