The protocol successfully halogenated a diverse collection of pharmaceuticals and agrochemicals, demonstrating its utility for late-stage functionalization. We obtained moderate yields of iodinated vismodegib, bisacodyl, and nicoboxil (72-74). Loratadine proved challenging in the one-pot process, but we could synthesize iodo-, bromo-, and chloro-analogs when we isolated the intermediate Zincke imine (75-77). Nicotine, Boc-protected niaprazine, etoricoxib, and quinoxyfen were competent substrates (78-82). The dihalogenation sequence is also amenable to complex pyridines. Using the basal-cell carcinoma treatment vismodegib, we obtained iodochloro analog 83 in reasonable yield over two steps. In summary, we have developed a 3-selective pyridine halogenation protocol that proceeds via a one-pot ring-opening, halogenation, ring-closing process. The reaction proceeds via NTf-Zincke imine intermediates that engage in a highly regioselective C-Hal bond-forming reaction before ring-closing using ammonia salts or acids. The process functions on various pyridine building blocks, drug-like intermediates, and is viable for late-stage functionalization applications. Given the lack of alternative methods for this transformation and the high value of the halopyridine products, we anticipate that this strategy will be useful for developing medicines and agrochemicals. This approach for pyridine functionalization is likely amenable for numerous other bond constructions that we will report in due course.