Recent Advances in Ammonium Iodide (NH 4 I)‐Mediated Transformations: Toward Greener and Metal‐Free Organic Synthesis

Ammonium iodide (NH 4 I) has recently emerged as a versatile and sustainable reagent in modern organic synthesis. This inexpensive and readily available inorganic salt serves as a redox mediator, promoter, and mild iodide source, enabling a broad spectrum of C–C, C–heteroatom, heteroatom–heteroatom, and one‐pot multibond‐forming reactions under environmentally benign conditions. Its dual functionality as both a nucleophilic iodide donor and an oxidative promoter has facilitated diverse transformations, including oxidative couplings, cyclizations, halogenations, and heterocyclic syntheses. This review provides a comprehensive overview of NH 4 I‐mediated thermal, photochemical, and electrochemical methodologies reported from 2020 to the present, emphasizing key mechanistic features, reaction scopes, and synthetic applications. By consolidating these recent advancements, this work underscores the growing importance of ammonium iodide as an efficient, green, and metal‐free mediator in contemporary organic synthesis and aims to inspire further innovation in sustainable, energy‐efficient, and environmentally responsible chemical transformations.