An Efficient Sequential One‐Pot Approach for the Synthesis of C3‐Functionalized Imidazo[1,2‐a]pyridines under Transition‐Metal Free Conditions

Abstract A metal‐free sequential one‐pot three‐component protocol is described for the synthesis of C3‐functionalized imidazo[1,2‐ a ]pyridines. A successive construction of imidazo[1,2‐ a ]pyridine followed by iodine‐catalysed sulfenylation has been achieved in a one‐pot operation from readily available α‐bromomethyl ketones, 2‐aminopyridines and thiosulfonates. An immense array of 3‐sulfenylimidazo[1,2‐ a ]pyridines were obtained in good to high yields. Also, the method extended for the synthesis of C3‐halogenated imidazo[1,2‐ a ]pyridines using sodium halides in the presence of K 2 S 2 O 8 . Notably, the reaction between α‐bromomethyl ketones and 2‐aminopyridines in the presence of K 2 S 2 O 8 to yield 3‐bromo‐2‐aryl‐imidazo[1,2‐a]pyridines, thus implies α‐bromomethyl ketones also served as brominating agent. Overall, the present sequential one‐pot protocol is straightforward, operationally simple, tolerates a broad range of functional groups, and is reliable for gram‐scale experiments.