Rational Design of an Organotellurium Chalcogen Bonding Catalyst for Azetidine Activation

The application of chalcogen bonding catalysis has been largely confined to benchmark reactions due to the limited structural diversity and activating ability of the catalysts, especially those derived from tellurium. Herein, we present a group of rationally designed bis-telluronium catalysts and realize the first application of chalcogen bonding donor in catalyzing the [4 + 2] cycloaddition reaction between azetidines and non-activated alkenes or alkynes. This chemistry demonstrates excellent functional group tolerance and offers an efficient avenue to access the piperidine and tetrahydropyridine architectures in generally moderate-to-good efficiency. A wide array of mechanistic experiments and DFT calculations have been performed to verify the high activity of the organotellurium catalysts with strong electron-deficient aromatic substituents and to suggest a novel bidentate activation mode between catalyst and azetidine via Te⋯O interaction.