Merging Gold Catalysis and Bronsted Acid Catalysis for the Synthesis of Tetrahydrobenzo[b][1,8]naphthyridines

A gold(I)/BrOnsted acid-catalyzed cyclization of 2-azidobenzaldehydes with 3-aza-1,6-enynes has been developed for the synthesis of tetrahydrobenzo[b][1,8]naphthyridine derivatives. This protocol enabled the modular synthesis of tetracyclic heterocycles in one operation with water and nitrogen gas as the byproducts.