title: The [2 + 2] Cycloaddition-Retroelectrocyclization and [4 + 2] Hetero-Diels-Alder Reactions of 2-(Dicyanomethylene)indan-1,3-dione with Electron-Rich Alkynes: Influence of Lewis Acids on Reactivity.
abstract: The reaction of electrophilic 2-(dicyanomethylene)indan-1,3-dione (DCID) with substituted, electron-rich alkynes provides two classes of push-pull chromophores with interesting optoelectronic properties. The formal [2 + 2] cycloaddition-retroelectrocyclization reaction at the exocyclic double bond of DCID gives cyanobuta-1,3-dienes, and the formal [4 + 2] hetero-Diels-Alder (HDA) reaction at an enone moiety of DCID generates fused 4H-pyran heterocycles. Both products can be obtained in good yield and excellent selectivity by carefully tuning the reaction conditions; in particular, the use of Lewis acids dramatically enhances formation of the HDA adduct.
authors.affiliation: †Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
authors.forename: Etienne J
authors.initials: EJ
authors.lastname: Donckele
authors.affiliation: †Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Finke
authors.affiliation: ‡Laboratoire d' Electrochimie et de Chimie Physique du Corps Solide, Institut de Chimie-UMR 7177, C.N.R.S., Université de Strasbourg, 4 rue Blaise Pascal, 67081 Strasbourg Cedex, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Ruhlmann
authors.affiliation: ‡Laboratoire d' Electrochimie et de Chimie Physique du Corps Solide, Institut de Chimie-UMR 7177, C.N.R.S., Université de Strasbourg, 4 rue Blaise Pascal, 67081 Strasbourg Cedex, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Boudon
authors.affiliation: †Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
authors.forename: Nils
authors.initials: N
authors.lastname: Trapp
authors.affiliation: †Laboratorium für Organische Chemie, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
authors.forename: François
authors.initials: F
authors.lastname: Diederich