RESUMO
A new strategy for the synthesis of the title compounds via a regio- and chemoselective one-pot inter- and intramolecular Buchwald-Hartwig amination of 2-chloro-3-iodopyridine with aminoazines and -diazines is reported.
Assuntos
Compostos Aza/síntese química , Imidazóis/síntese química , Compostos Organometálicos/química , Paládio/química , Piridinas/síntese química , Amidinas/química , Aminação , Catálise , Imidazóis/química , Estrutura MolecularRESUMO
Evidence for an interphase deprotonation of Pd(II)-amine complexes with weak carbonate base has been gained for the first time. When a rate-limiting deprotonation step is involved in the catalytic cycle, controlling the structure (shape and size of the particles) and/or molar excess of the carbonate base used can significantly increase the reaction rate of Buchwald-Hartwig aminations. By taking such a "base effect" into account a general protocol for the intermolecular amination of aryl iodides with all types of amines has been developed based on a standard Pd-BINAP catalyst, using cesium carbonate as the base.