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Synthesis of Dicyano‐Substituted Benzo[c]fluorenes from Tetraaryl[3]cumulenes
Author(s) -
Gawel Przemyslaw,
Halabi Elias A.,
Schweinfurth David,
Trapp Nils,
Ruhlmann Laurent,
Boudon Corinne,
Diederich François
Publication year - 2016
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201600470
Subject(s) - cumulene , chemistry , fluorene , cycloaddition , aromaticity , ring (chemistry) , chromophore , molecule , spectroscopy , photochemistry , electron paramagnetic resonance , stereochemistry , computational chemistry , organic chemistry , polymer , physics , nuclear magnetic resonance , quantum mechanics , catalysis
We have developed a one‐step synthesis of 5,6‐dicyano‐7‐(diphenylvinyl)‐7 H ‐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.