Application of thiopyrylium trifluoromethanesulfonates as Lewis acids in organocatalytic reactions

The successful application of thiopyrylium trifluoromethanesulfonate (triflate) as organic Lewis-acidic catalysts in electro-philic aromatic bromination, acetalization, cascade, and three-component reactions is disclosed. All these transformations provided the desired products in good yield. In particular, a catalytic amount of thiopyrylium triflate was used to activate <i>N</i>-bromosuccinimide for the bromination of various aromatic compounds under ambient and dark conditions.