title: Organocatalytic, Asymmetric Eliminative [4+2] Cycloaddition of Allylidene Malononitriles with Enals: Rapid Entry to Cyclohexadiene-Embedding Linear and Angular Polycycles.
abstract: A direct aminocatalytic synthesis has been developed for the chemo-, regio-, diastereo-, and enantioselective construction of densely substituted polycyclic carbaldehydes containing fused cyclohexadiene rings. The chemistry utilizes, for the first time, remotely enolizable π-extended allylidenemalononitriles as electron-rich 1,3-diene precursors in a direct eliminative [4+2] cycloaddition with both aromatic and aliphatic α,β-unsaturated aldehydes. The generality of the process is demonstrated by approaching 6,6-, 5,6-, 7,6-, 6,6,6-, and 6,5,6-fused ring systems, as well as biorelevant steroid-like 6,6,6,6,5- and 6,6,6,5,6-rings. A stepwise reaction mechanism for the key [4+2] addition is proposed as a domino bis-vinylogous Michael/Michael/retro-Michael reaction cascade. The utility of the malononitrile moiety as traceless activating group of the dicyano nucleophilic substrates is demonstrated.
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27A, 43124 Parma (Italy).|Dipartimento di Scienze degli Alimenti, Università degli Studi di Parma, Parma (Italy).
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Brindani
authors.affiliation: Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Traversa La Crucca 3, 07100 Li Punti Sassari (Italy). gloria.rassu@icb.cnr.it.
authors.forename: Gloria
authors.initials: G
authors.lastname: Rassu
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27A, 43124 Parma (Italy).|Institute of Chemical Research of Catalonia, Tarragona (Spain).
authors.forename: Luca
authors.initials: L
authors.lastname: Dell'Amico
authors.affiliation: Istituto di Chimica Biomolecolare, Consiglio Nazionale delle Ricerche, Traversa La Crucca 3, 07100 Li Punti Sassari (Italy).
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Zambrano
authors.affiliation: Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari, Sassari (Italy).
authors.forename: Luigi
authors.initials: L
authors.lastname: Pinna
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27A, 43124 Parma (Italy).
authors.forename: Claudio
authors.initials: C
authors.lastname: Curti
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27A, 43124 Parma (Italy).
authors.forename: Andrea
authors.initials: A
authors.lastname: Sartori
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27A, 43124 Parma (Italy).
authors.forename: Lucia
authors.initials: L
authors.lastname: Battistini
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27A, 43124 Parma (Italy).
authors.forename: Giovanni
authors.initials: G
authors.lastname: Casiraghi
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Parma, Parma (Italy).
authors.forename: Giorgio
authors.initials: G
authors.lastname: Pelosi
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27A, 43124 Parma (Italy).
authors.forename: Daniela
authors.initials: D
authors.lastname: Greco
authors.affiliation: Dipartimento di Farmacia, Università degli Studi di Parma, Parco Area delle Scienze 27A, 43124 Parma (Italy). franca.zanardi@unipr.it.
authors.forename: Franca
authors.initials: F
authors.lastname: Zanardi
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis* / Q000737:chemistry; D000498:Allyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D002384:Catalysis; D061565:Cycloaddition Reaction; D053138:Cyclohexenes / Q000138:chemical synthesis / Q000737:chemistry*; D009570:Nitriles / Q000138:chemical synthesis / Q000737:chemistry*; D011083:Polycyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D000498:Allyl Compounds; D053138:Cyclohexenes; D009570:Nitriles; D011083:Polycyclic Compounds; C048401:1,4-cyclohexadiene; C000945:dicyanmethane
keywords: asymmetric catalysis; carbocycles; cycloaddition; organocatalysis; synthetic methods