Axially Chiral ( R )-BINOL-, ( R )-BINAM-, and ( R )-NOBIN-Stabilized Palladium Nanoparticles for Highly Enan

Abstract

Chiral palladium nanoparticles (PdNPs) stabilized by axially chiral 1,1′-bi-2-naphthol ((R)-BINOL), (R)-[1,1′-binaphthalene]-2,2′-diamine ((R)-BINAM), and (R)-2-amino-1,1′-binaphthalen-2-ol ((R)-NOBIN) ligands were synthesized and evaluated as heterogeneous catalysts for asymmetric Suzuki-Miyaura cross-coupling reactions. Structural and spectroscopic analyses confirmed the formation of crystalline PdNPs with narrow size distributions (2.4–2.7 nm) and ligand-induced surface chirality. Under the optimized conditions, the catalysts consistently provided high enantioselectivities, reaching ≥99% ee over a broad substrate scope comprising diverse aryl halides and boronic acids. Enantioinduction originates from the chiral environment at the nanoparticle surface, whereas catalytic efficiency is primarily determined by the steric and electronic properties of the substrate and the identity of the leaving group. (R)-BINAM-stabilized PdNPs provided superior conversions, which can be attributed to the two amine (−NH2) groups in (R)-BINAM that enable stronger metal–ligand interactions at the Pd surface. Poisoning, hot filtration, and recycling experiments support predominantly heterogeneous catalysis and demonstrate retention of activity and enantioselectivity over multiple cycles. These findings establish chiral PdNPs as efficient, reusable, and highly enantioselective catalysts for the synthesis of axially chiral biaryls.