title: A New Palladium-Catalyzed Intramolecular Allylation to Pyrrolidin-2-ones(1).
abstract: A novel palladium(0)-catalyzed cyclization to 3,4-disubstituted pyrrolidin-2-ones has been developed. The new approach relies upon the concomitant generation of stabilized acetamide enolate anions and of a pi-allyl-palladium appendage, properly tethered by a nitrogen atom. Reaction conditions have been optimized for the methoxycarbonyl-stabilized model reaction [(Z)-2 --> 3] and then applied to other substrates. A broad range of acetamide anion stabilizers was shown to allow the desired intramolecular C-C bond formation (MeO(2)C, MeCO, NC, (EtO)(2)PO, PhSO(2)). The cyclizations gave exclusively 5-exo-trig ring closure, thereby affording gamma-lactams. All the cyclizations gave the corresponding 3,4-disubstituted pyrrolidin-2-ones with total diastereoselection. Complete trans preference was unequivocally demonstrated for the model reaction via a NOESY experiment.
authors.affiliation: Dipartimento di Chimica Organica "Ugo Schiff" and CNR Centro de Studio sulla Chimica e la Struttura dei Composti Eterocicli e loro Applicazioni, Via G. Capponi 9, I-50121, Firenze, Italy.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Giambastiani
authors.forename: Barbara
authors.initials: B
authors.lastname: Pacini
authors.forename: Marina
authors.initials: M
authors.lastname: Porcelloni
authors.forename: Giovanni
authors.initials: G
authors.lastname: Poli