Synthesis of 5H-thiazolo[2′,3′:2,3]imidazo[4,5-b]indole Fused Hybrid Structures via Copper-Catalyzed Sequential C-N Coupling Reactions

In this study, we developed a simple and efficient synthetic procedure to obtain novel imidazothiazole-indole fused hybrid compounds through sequential C-N coupling reactions using copper catalysts. The key reaction was performed between 5-bromo-6-(2-bromophenyl)imidazo[2,1-b]thiazole derivatives and various amines, allowing for a significant expansion of the structural scope of the products compared to the use of nitrile derivatives. Optimal reaction conditions were identified, employing the CuI/ethyl 2-oxocyclohexane-1-carboxylate catalyst system, providing high overall yields (76-85%). Using this method, we successfully synthesized four new compounds (7c-f). The structures of all compounds were confirmed by 1H-NMR and 13C-NMR spectroscopy. This work presents a valuable contribution to the field of heterocyclic chemistry, offering a practical and versatile approach for the synthesis of diverse imidazothiazole-indole hybrids with potential applications in medicinal chemistry and materials science.