Liu, R.; Fu, Y.; Wu, F.; Liu, F.; Zhang, J.J.; Yang, L.; Popov, A.A.; Ma, J.; Feng, X.: Modular Synthesis of Structurally Diverse Azulene-Embedded Polycyclic Aromatic Hydrocarbons by Knoevenagel-Type Condensation. Angewandte Chemie - International Edition 62 (2023), p. e202219091/1-7
10.1002/anie.202219091
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Abstract:
The research interest in azulene-embedded polycyclic aromatic hydrocarbons (PAHs) has significantly increased recently, but the lack of efficient synthetic strategies impedes the investigation of their structure-property relationships and further opto-electronic applications. Here we report a modular synthetic strategy towards diverse azulene-embedded PAHs by a tandem Suzuki coupling and base-promoted Knoevenagel-type condensation with good yields and great structural versatility, including non-alternant thiophene-rich PAHs, butterfly- or Z-shaped PAHs bearing two azulene units, and the first example of a two-azulene-embedded double [5]helicene. The structural topology, aromaticity and photophysical properties were investigated by NMR, X-ray crystallography analysis and UV/Vis absorption spectroscopy assisted by DFT calculations. This strategy provides a new platform for rapidly synthesizing unexplored non-alternant PAHs or even graphene nanoribbons with multiple azulene units.