title: Nucleophilic addition/double cyclization cascade processes between enynyl Fischer carbene complexes and alkynyl malonates.
abstract: Two new selective cascade processes for enynyl Fischer carbene complexes 1 are described in their reaction with alkynyl malonates. When carbene complexes 1 react with the sodium enolate of homopropargyl malonates 3 a consecutive Michael-type addition/cyclopentannulation/6-exo cyclization takes place leading, in a regio- and stereoselective way, to n/5/6 angular tricyclic compounds 5. Furthermore, when propargylic malonates are used, a delayed protonation of the reaction mixture allows intermediate 1,4-addition adduct Ia to evolve through a 5-exo cyclization, consisting of an intramolecular nucleophilic attack from the central carbon of the allenylmetallate over the triple C-C bond. Further spontaneous cyclopentannulation of the resulting metallatriene gives rise to bicyclic and linear polycyclic compounds 6 and 7, some of them bearing a polyquinane framework.
authors.affiliation: Departamento de Química Orgánica e Inorgánica, Universidad de Oviedo , Julián Clavería 8, 33071 Oviedo, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Álvarez-Fernández
authors.forename: Tatiana
authors.initials: T
authors.lastname: Suárez-Rodríguez
authors.forename: Ángel L
authors.initials: ÁL
authors.lastname: Suárez-Sobrino