Trimethylsulfoxonium bromide is widely used as a methylating agent in organic synthesis. It facilitates the transfer of methyl groups to various substrates, making it valuable in the production of pharmaceuticals and fine chemicals. The compound is particularly effective in methylation reactions involving nucleophiles such as alcohols, amines, and thiols. It is also employed in the synthesis of dimethylsulfoxonium methylide, a key intermediate in the Corey-Chaykovsky reaction, which enables the formation of epoxides from aldehydes and ketones, as well as cyclopropanes from α,β-unsaturated carbonyl compounds. Additionally, its stability and reactivity make it a preferred reagent in laboratory settings for selective methylation processes and other specialized synthetic transformations.