Abstract
We have developed a one‐step synthesis of 5,6‐dicyano‐7‐(diphenylvinyl)‐7H‐benzo[c]fluorenes, starting from easily accessible tetraaryl[3]cumulenes and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). In the proposed mechanism, this transformation is initiated by single‐electron transfer from the cumulene to DDQ with subsequent ring closure. In the next step, [4+2] cycloaddition of an additional DDQ molecule is followed by transformation of the formed cycloadducts, which provides new 5,6‐dicyanobenzo[c]fluorene derivatives in fair to good yields. Isolated intermediates and time‐resolved EPR spectroscopy measurements support our mechanistic proposal. Furthermore, X‐ray crystallographic proof for the postulated structures as well as for the reaction intermediates is provided. The optoelectronic properties of these new chromophores were derived from UV/Vis spectroscopy, electrochemical, and computational studies. Additionally, the aromaticity of the new polycyclic aromatic backbone was analyzed by using nucleus‐independent chemical shift (NICS)‐XY‐scans.
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