Well-defined chiral dinuclear copper complexes in enantioselective propargylic substitution: For a long-standing supposition on binuclear mechanism

Despite binuclear Cu active sites present in some biological and heterogeneous catalysts, the development of chiral binuclear copper catalysts is still in its infancy and remains a formidable challenge. A notable example is that the asymmetric propargylic substitution catalyzed by a chiral binuclear Cu complex is still unknown, although some kinds of in-situ-assembled binuclear Cu species have frequently been proposed as active intermediates. Herein, we report a series of binuclear copper catalysts supported by chiral benzo [c] cinnoline dioxazoline frameworks, which demonstrated high efficiency in (dynamic) kinetic resolution of propargylic alcohol derivatives via propargylic substitution. Mechanistic investigations suggested that the binuclear Cu core shows a bifunctional role in coordination with acetylide and allenylidene ligands. These findings shed light onto the long-standing mechanistic ambiguity, providing solid support for the proposal that the binuclear Cu core can be crucial for substrate activation and selectivity control in catalysis.