1,2-Dimethylisothiourea hydriodide is a key reagent in organic synthesis, particularly for the preparation of guanidine derivatives via reaction with primary amines. It is widely used in the synthesis of heterocyclic compounds, such as thiazoles and triazoles, which serve as important building blocks in pharmaceuticals, agrochemicals, and materials science. In medicinal chemistry, it acts as a precursor for compounds exhibiting antimicrobial, antifungal, and anticancer activities. Its versatility stems from the reactivity of the isothiourea moiety, making it essential in advanced research and development applications.