Asymmetric Tellurium-Bonding Catalysis for Mannich Reaction.

Chalcogen-bonding catalysis has recently emerged as a powerful tool in organocatalysis. Nevertheless, its application in asymmetric transformations remains largely unexplored, primarily due to the scarcity of efficient chiral chalcogen-bond donors. In this study, we report the design and synthesis of a series of chiral tellurium-bonding catalysts based on an axially chiral 1,1'-spirobiindane scaffold. Taking advantage of the highly directional and strongly polarizable tellurium-centered donors along with a well-defined C2-symmetric chiral environment, these catalysts enable cooperative bifunctional activation of substrates. Under optimized conditions, the asymmetric Mannich reaction of isatin imines with dicyanoolefins proceeds smoothly to afford a broad range of products in good to excellent yields with high enantioselectivities. Mechanistic studies support a dual chalcogen-bonding activation mode involving cooperative interactions between the two tellurium centers and the isatin imine substrate. This work constitutes a seminal contribution to asymmetric catalysis enabled by chalcogen bonding and offers a new platform for the development of chiral tellurium-bonding catalysts and related enantioselective transformations.