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 GaCl 4 – counteranion while employing the cyclizations of 2 H -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 GaCl 4 – ···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.