Used primarily as an intermediate in organic synthesis, especially in the pharmaceutical and agrochemical industries. It serves as a key building block for sulfonamide-based compounds, which are common in bioactive molecules. Its sulfonyl chloride group readily reacts with amines to form sulfonamides, making it valuable in drug development for creating libraries of compounds with potential antimicrobial, anti-inflammatory, or central nervous system activity. Also employed in the synthesis of dyes and fluorescent probes due to the indole backbone’s inherent optical properties. Its reactivity and structural features allow for functionalization in heterocyclic chemistry, supporting the design of novel compounds in research settings.