Dimethyl sulfate is primarily used as a methylating agent in organic synthesis. It transfers methyl groups to nucleophiles such as amines, phenols, and thiols, making it valuable in the production of pharmaceuticals, dyes, and agrochemicals. It is especially effective in the methylation of aromatic hydroxyl groups in phenolic compounds, which is a key step in synthesizing certain drugs and antioxidants. Due to its high reactivity, it is also employed in the preparation of quaternary ammonium compounds and in modifying natural products. However, because of its toxicity and carcinogenic nature, its use is often limited to controlled industrial settings with strict safety protocols.