Used primarily as an intermediate in organic synthesis, especially in the preparation of sulfa drugs and other biologically active compounds. Its aldehyde and sulfonyl chloride functional groups allow for dual reactivity, enabling sequential or selective transformations. Commonly employed in the development of sulfonamide-based pharmaceuticals through reaction with amines. Also utilized in the synthesis of dyes, fluorescent probes, and polymer modifiers due to its ability to introduce reactive handles into molecular frameworks. Its bifunctional nature makes it valuable in cross-coupling reactions and the construction of complex aromatic systems.