title: Intramolecular C-H activation by alkylpalladium(II) complexes: insights into the mechanism of the palladium-catalyzed arylation reaction.
abstract: The cyclization of [ArOCH2PdL2Cl] complexes proceeds at room temperature in CH3CN in the presence of base, such as KOPh or carbonate, to form palladacycles. The effect of substituents on the aryl moiety (p-MeO > H >p-NO2) is as expected for an electrophilic aromatic substitution by electrophilic Pd(II). The absence of isotopic effect is also consistent with this proposal. Cyclopalladation proceeds with bidentate ligands (dppf, COD and phen); although the C-H activation reactions are slower in these cases. The starting [ArOCH2Pd(PPh3)2Cl] and [ArOCH2Pd(PPh3)Cl]2 complexes were prepared by transmetalation of organostannanes [(ArOCH2)4Sn] with [Pd(PPh3)2Cl2] or [Pd(PPh3)Cl2]2, respectively. Cleavage of palladacycles with HCl also gave [ArOCH2PdL2Cl] complexes.
authors.affiliation: Dpto Química Orgánica (C-I), Facultad de Ciencias, Universidad Autónoma de Madrid, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Martín-Matute
authors.forename: C
authors.initials: C
authors.lastname: Mateo
authors.forename: D J
authors.initials: DJ
authors.lastname: Cárdenas
authors.forename: A M
authors.initials: AM
authors.lastname: Echavarren