Dynamic palladium catalysis enables chiral amplification toward acyclic Schiff base atropisomers.

Abstract

Schiff bases, despite their structural versatility and broad applications, have remained elusive as acyclic atropisomers due to synthetic challenges. Herein, we report a palladium-catalyzed asymmetric N-allylation of diarylmethanimines with allylic precursors, enabling the construction of acyclic Schiff base atropisomers bearing C-C axes. Crucially, dynamic ligand exchange between the imine substrates and the palladium pre-catalyst drives its evolution from a less active to a more reactive species. This self-optimizing system leads to a unique time-dependent enhancement of enantioselectivity up to 96% ee. Experimental and density functional theory studies reveal that substrate-induced reorganization of the catalytic system optimizes the reaction pathway, leading to high yields (up to 83%) and absolute Z stereoselectivity. The method exhibits remarkable functional group tolerance and scalability, and its utility is demonstrated through diverse transformations. This work provides efficient access to previously inaccessible atropisomeric scaffolds and establishes a paradigm of substrate-guided catalyst evolution for asymmetric catalysis.