A Second-Generation Catalyst for Aryl Halide Amination: Mixed Secondary Amines from Aryl Halides and Primary Amines Catalyzed by (DPPF)PdCl_2

摘要

Aromatic amines are important substructures in natural products and organic materials. Our group and Buchwald's have recently reported the palladium-catalyzed amination of ary1 halides in the presence of alkoxide and amide bases that significantly improved upon amination procedures employing toxic and air sensitive aminostannanes. Although these methods gave high yields with secondary amines and aryl bromides, a general high-yielding intermolecular amination procedure involving primary amine substrates or aryl iodide electrophiles had not been developed. The catalysts used for intermolecular animations contained tri-o-tolylphosphine as the ligand. Our mechanistic studies have shown that each complex on the reaction coordinate involving this catalystis a monomeric, monophosphine species. The large size of this ligand leads to fast reaction rates by favoring low coordination number compounds and high selectivity for arylamine formation by favoring reductive elimination of arylamine over β-hydrogenelimination of imine.