Violet‐Light‐Induced Dichlorination of Imidazo[1,2‐ <i>a</i> ]pyridines Under Metal/Base/Oxidant Free Conditions

Abstract We report herein an effective violet‐light‐induced protocol for the dichlorination and bromosaccharin‐based disubstitution of imidazo[1,2‐ a ]pyridines under mild, metal‐, and oxidant‐free conditions. Using N‐chlorosuccinimide (NCS) and trimethylsilyl chloride (TMSCl) under 390 nm LED irradiation, a variety of imidazo[1,2‐ a ]pyridine derivatives were converted to their corresponding dichlorinated products in moderate to good yields. Notably, replacement of NCS with N‐bromosaccharin enabled a C3, C5‐disubstitution reaction, affording sulfonyl‐functionalized imidazopyridine derivatives with potential relevance in medicinal and materials chemistry. The methodology was successfully demonstrated on a gram scale, and control experiments revealed that the reaction proceeds through an ionic pathway.