Copper-Catalyzed Cascade Acylation/Coupling Cyclization Process for the Synthesis of Polycyclic Fused Imidazo[2,1--b][1,3]thiazinones

A new and efficient cascade synthesis of polycyclic fused imidazo[2,1-b][1,3]thiazinones has been developed. This protocol includes an intermolecular N-acylation followed by a copper-catalyzed intramolecular CS coupling reaction. The methodology is applied to a wide range of 2-iodo, 2-bromo, and 2-chloro benzoyl chlorides to yield the polycyclic fused imidazo[2,1-b][1,3]thiazinones in good to excellent yields.