title: Solvent/base effects in the selective domino synthesis of phenanthridinones that involves high-valent palladium species: experimental and theoretical studies.
abstract: The domino reaction of o-bromobenzamides 1a-m in the presence of K(2)CO(3) and the [PdCl(2)(PPh(3))(2)] catalyst granted a selective access to phenanthridinones 2 or to the new 1-carboxamide phenanthridinones 3 depending on the solvent, DMF or 1,4-dioxane, respectively. Investigations of the reaction parameters provided the first example of a direct correlation between the base dissociation and the solvent polarity on the selectivity observed. Moreover, mechanistic studies (NMR spectroscopy and ESI-MS monitoring) allowed us to characterize Pd(II) palladacycle 4 and biaryl species as common intermediates for these two domino processes. On that basis, C(sp(2))-C(sp(2)) bond formation is envisaged by generation of a Pd(IV) complex after oxidative addition of 1 into Pd(II) palladacycle 4, a rationale that is supported by DFT calculations. A general catalytic cycle is proposed to account for these observations.
authors.affiliation: Laboratoire de Pharmacognosie UMR CNRS 8638, Université Paris Descartes, Paris, France.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Donati
authors.forename: Pascale
authors.initials: P
authors.lastname: Leproux
authors.forename: Elise
authors.initials: E
authors.lastname: Prost
authors.forename: Sylvie
authors.initials: S
authors.lastname: Michel
authors.forename: François
authors.initials: F
authors.lastname: Tillequin
authors.forename: Vincent
authors.initials: V
authors.lastname: Gandon
authors.forename: François-Hugues
authors.initials: FH
authors.lastname: Porée
mesh_terms: D001549:Benzamides / Q000737:chemistry; D002384:Catalysis; D008962:Models, Theoretical; D015394:Molecular Structure; D010165:Palladium / Q000737:chemistry*; D010616:Phenanthrenes / Q000138:chemical synthesis* / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism
chemical_list: D001549:Benzamides; D010616:Phenanthrenes; D012997:Solvents; D010165:Palladium