Copper-Catalyzed Asymmetric Nucleophilic Opening of 1,1,2,2-Tetrasubstituted Donor–Acceptor Cyclopropanes for the Synthesis of α-Tertiary Amines

Catalytic asymmetric transformation of donor-acceptor cyclopropanes (DACs) has been proven to be a highly valuable and robust strategy to construct diverse types of enantioenriched molecules. However, the use of 1,1,2,2-tetrasubstituted DACs to form products bearing quaternary stereocenters remains a long-term unsolved challenge. Here, we report the copper-catalyzed asymmetric aminative ring opening of tetrasubstituted alkynyl DACs that delivers a myriad of α-tertiary amines with high levels of enantioselectivities. The alkyne, amine, and ester moieties within the products enable diverse further applications, including the asymmetric synthesis of bioactive molecules. Mechanistic studies indicate that the zwitterionic intermediate bearing a copper-acetylide unit plays a key role in the process, which represents a new mode for achieving catalytic asymmetric transformation of DACs.