Palladium-catalyzed amination reactions provide a powerful means of creating carbon-nitrogen bonds from readily available aryl halides or triflates. These reactions are known to be highly sensitive to the structures of both substrate and ancillary ligand, but little information is available regarding potential deactivation pathways or side reactions. Binapththyl 2-triflates bearing various aryl or alkyl 2'-substituents represent a challenging substrate class for amination given the significant steric bulk adjacent to the substitution site. Yields in palladium-catalyzed Buchwald-Hartwig aminations of these chiral synthons were found to depend strongly on the bite angle of the diphosphine ligand as well as the metal:ligand ratio. Under some conditions, a C-H arylation side process occurred, giving rise to chiral [5]helicene derivatives. Reaction conditions were tuned to provide either amination or C-H arylation products for a range of substrates. The former are precursors for a new family of monodentate chiral carbene ligands, while the latter have potential materials applications.

Unusual ligand effects and unexpected C-H arylation side reactions in palladium-catalyzed amination reactions en route to new monodentate binaphthyl-based ligands

247th National Meeting (2014)

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