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

Nicolas Kerisit (1) , Aaron D. Finke (2) , Nils Trapp (2) , Yann R. Leroux (1) , Jean-Claude Guillemin (1) , Yann Trolez (1) , François Diederich (2)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 ETH Zürich - Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich]

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).

Mots clés: Pentafulvenes; [2+2] Cycloaddition; Electrocyclization; [3]Cumulene; dihydropentalene

Domaines: Chimie; Chimie organique

Nicolas Kerisit, Aaron D. Finke, Nils Trapp, Yann R. Leroux, Jean-Claude Guillemin, et al.. New reactivity of 6,6-bis-donor-substituted pentafulvenes: one-step synthesis of highly substituted [3]cumulene and dihydropentalene. Tetrahedron, 2015, 71 (25), pp.4393-4399. ⟨10.1016/j.tet.2015.03.081⟩. ⟨hal-01141537⟩