Diastereoselective and enantiospecific direct reductive amination in water catalyzed by palladium nanoparticles stabilized by polyethyleneimine derivatives

Alkylated polyethylenimine or homochiral polyethylenimine derivatives, or both, were used to stabilize palladium nanoparticles dispersed in water. Such constructs have hydrophobic regions that enabled the aqueous biphasic hydrogenation of imines formed in situ by the reaction of ketones and chiral primary amines. In the presence of MgCl₂, good yields of the direct amination product were obtained with high diastereoselectivity. In the presence of a homochiral polyethylenimine, enantiospecific direct amination was observed via kinetic resolution, ostensibly as a result of preferred access of one enantiomer to the achiral reaction center.