Chemoselective iodination of 6-substituted imidazo[1,2-a]pyridine

Synthesis and Evaluation of Photophysical Properties of C‐3 Halogenated Derivatives of 2‐Phenylimidazo[1,2‐a]pyridine

“…A variety of synthetic methods have been reported for the preparation of C‐3 halogenated imidazo[1,2‐ a ]pyridines. At present, the main strategy is to use NXS, [ 26‐28 ] NaX, [ 29‐30 ] tetra‐ n ‐butyl ammonium halide, [ 31 ] I 2 [ 32 ] as halogen sources and synthesize them by electrochemical oxidation, [ 33‐35 ] photochemical oxidation [ 36 ] and metal oxidation catalysis. [ 37 ] Furthermore, imidazole zwitterionic molten salt, [ 38 ] new chlorination reagent chloramine‐T [ 39 ] or pyridine tribromide [ 40 ] plasma catalytic system have also been used as halogen source or catalyst in C‐3 halogenation reaction over recent years.…”

Recent Progress in Transition Metal-Free C-Heteroatom Bond Formation by Functionalization of C-H Bond in Imidazole-Fused Heterocycles

“…In 2018, Zhao and co-workers [48] investigated the chemose-lectivity of the iodination of 6-substituted imidazo[1,2-a]-pyridine through experiment and theoretical calculations. The iodination reaction occurred at C-3 position both under action of NIS and I 2 -morpholine when 6-unsubstituted and trifluoromethyl-imidazo[1,2-a]pyridines were used as starting materials, while using 6-nitroimidazo[1,2-a]pyridine as substrates, reaction with NIS afforded the 3-iodo-6-nitroimidazo[1,2-a]pyridine and 8-iodo-6-nitroimidazo[1,2-a]pyridine was obtained in the presence of I 2 -morpholine.…”

I2O5-Mediated Iodocyclization Cascade of N-(1-Arylallyl)pyridine-2-amines with Concomitant C═C Bond Cleavage: A Synthesis of 3-Iodoimidazo[1,2-a]pyridines

“…Among imidazo­[1,2- a ]­pyridine family, 3-halogenated imidazo­[1,2- a ]­pyridines have received special attention because they are versatile intermediates enabling the late-stage elaboration with the C–X (X = Cl, Br, I) bonds . The traditional methods for the preparation of 3-halogenated imidazo­[1,2- a ]­pyridines relied on stepwise synthesis via 3-halogenation of preformed imidazo­[1,2- a ]­pyridines with certain halogen sources . Several straightforward methods have been explored including CuO x /OMS-2-catalyzed three-component reaction of 2-aminopyridine, acetophenones, and iodine; copper-catalyzed oxidative coupling between 2-aminopyridine and alkenes in the presence of iodine; copper-mediated aerobic oxidative coupling/cyclization of pyridines and enamides; and transition-metal-free chlorocyclization cascade of 2-aminopyridines with aliphatic carboxylic acids or ketones .…”