Efficient Approach to Mesoionic Triazolo[5,1-a]isoquinolium through Rhodium-Catalyzed Annulation of Triazoles and Internal Alkynes.

Rhodium-catalyzed annulation reactions between triazoles and internal alkynes, leading to various mesoionic isoquinoliums, are described. The reaction involves sequential triazole-directed C-H activation and C-C, C-N, and C-O bond formation processes in a one-pot manner. The starting materials and catalysts are easily available. The reaction offers a facile and practical approach to mesoionic isoquinolium derivatives.