A Dinucleating Modular Phosphine–Pyridine–Oxazoline Ligand for Cu-Catalyzed Asymmetric Dearomative Propargylic Substitutions

Asymmetric catalysis enabled by dinucleating ligands remains markedly underdeveloped compared with the mature field of mononuclear asymmetric catalysis. Here, we report the development of a modular chiral dinucleating ligand based on a 6-phosphinylpyridine-oxazoline skeleton, which can undergo self-assembly upon coordination to form dinuclear complexes with a sterically confined chiral pocket. The catalytic capability and unique chiral environment of this ligand were evaluated by successfully applying it in two types of asymmetric dearomative propargylations, including a stereodivergent synthesis of spiroindolenines bearing two stereocenters. The diverse transformations of the chiral spirocyclic products, including the preparation of chiral dihydroanthracenes via rearrangement, established a versatile platform for accessing valuable molecular scaffolds. Furthermore, mechanistic investigations indicated that dinuclear species are involved in the catalytic cycle, with insights into the enantio-determining steps and the key orbital interaction in the dicopper-allenylidene intermediate.