title: Straightforward synthesis of 5-bromopenta-2,4-diynenitrile and its reactivity towards terminal alkynes: a direct access to diene and benzofulvene scaffolds.
abstract: The high-yielding synthesis of 5-bromopenta-2,4-diynenitrile (BrC5 N) was achieved for the first time. Its reactivity with triisopropylsilylacetylene and triisopropylsilylbutadiyne in the presence of copper and palladium as co-catalysts and diisopropylamine was evaluated. It revealed an unprecedented cascade reaction leading to a diene in one case and to a benzofulvene in the other case, with a unique structure. Both of them were characterized by X-ray crystallography, among other techniques. The mechanism of the reaction leading to the diene was investigated experimentally. Theoretical calculations at the DFT level suggest that the mechanism leading to the benzofulvene relies on a hexa-dehydro Diels-Alder (HDDA)-type of mechanism. This work constitutes an example of an unanticipated reactivity leading to an important increase of chemical complexity.
authors.affiliation: Ecole Nationale Supérieure de Chimie de Rennes, UMR 6226, CNRS, 11 allée de Beaulieu, CS 50837, 35708 Rennes Cedex 7 (France), Fax: (+33) 2-23-23-81-08.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Kerisit
authors.forename: Loïc
authors.initials: L
authors.lastname: Toupet
authors.forename: Paolo
authors.initials: P
authors.lastname: Larini
authors.forename: Lionel
authors.initials: L
authors.lastname: Perrin
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Guillemin
authors.forename: Yann
authors.initials: Y
authors.lastname: Trolez
keywords: acetylenic compounds; copper; hexa-dehydro Diels-Alder reaction; palladium; ynamine