Benzenesulfonyl isocyanate is primarily used as a reagent in organic synthesis, particularly for the introduction of the sulfonyl group into various compounds. It is commonly employed in the preparation of sulfonamides, which are valuable in pharmaceutical applications due to their antibacterial and antifungal properties. Additionally, it serves as a key intermediate in the synthesis of agrochemicals, dyes, and other specialty chemicals. Its reactivity with amines and alcohols makes it useful for modifying polymers and creating functionalized materials. In research, it is utilized for labeling and crosslinking biomolecules, aiding in the study of protein interactions and structures.