title: First example of stepwise, zwitterionic mechanism for bicyclo[2.2.1]hept-5-ene (norbornene) formation process catalyzed by the 1-butyl-3-methylimidazolium cations.
abstract: B3LYP/6-31++G(d) calculations indicated that the reaction of (2E)-3-phenyl-2-nitroprop-2-enenitrile with cyclopentadiene catalyzed by cations of 1,3-dialkylimidazolium ionic liquid shall not take place according to the classical scheme of one-step [2+4] Diels-Alder cycloaddition. Along the path finally leading to bicyclo[2.2.1]hept-5-ene (norbornene) with a nitro group inendoorientation, the process of bicarbocyclic skeleton formation shall take place according to the domino mechanism, via [2+4] heterocycloadduct. On the other hand, along the path leading finally to bicyclo[2.2.1]hept-5-ene with a nitro group inexoorientation, acyclic adduct with a zwitterionic nature is formed in the first reaction, which undergoes cyclisation next in the second step of the reaction.
authors.affiliation: Institute of Organic Chemistry and Technology, Cracow University of Technology, Cracow, Poland.
authors.forename: Radomir
authors.initials: R
authors.lastname: Jasiński
keywords: DFT study; Diels–Alder reaction; Mechanism; Nitroalkenes