NCBSI/KI: A Reagent System for Iodination of Aromatics through In Situ Generation of I‑Cl

In situ iodine monochloride (I-Cl) generation followed by iodination of aromatics using NCBSI/KI system has been developed. The NCBSI reagent requires no activation due to longer bond length, lower bond dissociation energy, and higher absolute charge density on nitrogen. The system is adequate for mono- and diiodination of a wide range of moderate to highly activated arenes with good yield and purity. Moreover, the precursor N-(benzenesulfonyl)­benzenesulfonamide can be recovered and transformed to NCBSI, making the protocol eco-friendly and cost-effective.