A Ternary Chalcogen-Bonding Counteranion-Binding Supramolecular Catalysis System

Herein, we describe a ternary chalcogen-bonding counteranion-binding supramolecular catalysis system that exploits a cationic chalcogen bonding catalyst to activate one reactant while simultaneously using the counteranion to activate another reactant. Beyond a dual-activation property, the two discrete reactants are assembled within a ternary supramolecular complex, enabling creating a favorable proximity condition. The proof-of-concept study on this catalysis system was implemented by using chalcogen bonding catalysts bearing a GaCl4– counteranion while employing the cyclizations of 2H-azirines with naphthols or hydroxyindole as benchmark reactions. Mechanistic investigation suggests that a ternary supramolecular system consisting of one catalyst and two reactants is operative, wherein Se···N interaction activates azirine to enhance its electrophilicity, while GaCl4–···H–O binding activates naphthol or hydroxyindole to improve the nucleophilicity. The advantage of this catalysis system is demonstrated by its capability to solve the reactivity problem, since conventional binary chalcogen-bonding catalysis system had no catalytic activity, while strong Lewis or Brønsted acids were either inactive or yielded complex mixtures at room temperature.