But-3-yn-1-yl methanesulfonate is primarily used as a reactive intermediate in organic synthesis. Its alkyne functional group makes it valuable for click chemistry reactions, particularly in the formation of triazoles through copper-catalyzed azide-alkyne cycloaddition (CuAAC). This compound is also employed in the modification of biomolecules, such as peptides and proteins, enabling the attachment of functional groups or labels for biochemical studies. Additionally, it serves as a building block in the synthesis of complex organic molecules, including pharmaceuticals and agrochemicals, due to its ability to introduce alkyne moieties into target structures. Its methanesulfonate group further enhances its reactivity, making it a versatile reagent in various chemical transformations.