Chalcogen-Bonding Catalysis with Telluronium Cations

Chalcogen bonding results from non-covalent interactions occurring between electrodeficient chalcogen atoms and Lewis bases. Among the chalcogens, tellurium is the strongest Lewis acid, but Te-based compounds are scarcely used as organocatalysts. For the first time, telluronium cations demonstrated impressive catalytic properties at low loadings in three benchmark reactions: the Friedel-Crafts bromination of anisole, the bromolactonization of omega-unsaturated carboxylic acids and the aza-Diels-Alder between Danishefsky's diene and imines. The ability of telluronium cations to interact with a Lewis base through chalcogen bonding was demonstrated on the basis of multi-nuclear (O-17, P-31, and Te-125) NMR analysis and DFT calculations.