New reactivity of 6,6-bis-donor-substituted pentafulvenes: one-step synthesis of highly substituted [3]cumulene and dihydropentalene

• Published in: Tetrahedron Vol. 71; no. 25; pp. 4393 - 4399
• Main Authors: Kerisit, Nicolas, Finke, Aaron D., Trapp, Nils, Leroux, Yann R., Guillemin, Jean-Claude, Trolez, Yann, Diederich, François
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 24.06.2015; Elsevier
• Subjects: [2+2] Cycloaddition; chemical reactions; Chemical Sciences; chemical structure; Chemistry; Chemistry, Organic; Cumulene; dihydropentalene; Electrocyclization; Organic chemistry; organic compounds; Pentafulvenes; Physical Sciences; Science & Technology; spectroscopy; X-radiation; Electrocyclization; Cumulene; [2+2] Cycloaddition; Pentafulvenes; dihydropentalene; CUMULENES; BENZENE; MONO; PUSH-PULL CHROMOPHORES; X-RAY; ACCESS; SEQUENTIAL 2+2 CYCLOADDITION; ELECTRONIC-STRUCTURE
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2015.03.081

We report the preparation of a 6,6-bis[(4-N,N-dimethylanilino)ethynyl]pentafulvene from a 6,6-dibromopentafulvene and 4-ethynyl-N,N-dimethylaniline under Sonogashira cross-coupling conditions. A push–pull [3]cumulene was formed unexpectedly during this reaction in moderate yield. The 6,6-bis[(4-N,N-dimethylanilino)ethynyl]pentafulvene was reacted with tetracyanoethylene, and an unprecedented 1,2-dihydropentalene was obtained in high yield as the exclusive product. The structures of the new compounds are supported by X-ray analysis, and a reasonable mechanism for their formation is proposed. We also report their interesting opto-electronic properties, as studied by UV/vis spectroscopy and cyclic voltammetry (CV). [Display omitted] A 6,6-bis[(4-N,N-dimethylanilino)ethynyl]pentafulvene has been prepared using a 6,6-dibromopentafulvene and 4-ethynyl-N,N-dimethylaniline under Sonogashira cross-coupling conditions. A push–pull [3]cumulene was formed unexpectedly during this reaction in moderate yield. The 6,6-bis[(4-N,N-dimethylanilino)ethynyl]pentafulvene was reacted with tetracyanoethylene, and an unprecedented 1,2-dihydropentalene was obtained in high yield as the exclusive product.