Isoquinoline-5-sulfonic acid is primarily used in the synthesis of various organic compounds, particularly in the development of dyes and pigments. Its sulfonic acid group makes it a valuable intermediate in creating water-soluble dyes, which are essential in the textile industry for coloring fabrics. Additionally, it serves as a building block in the production of pharmaceuticals, where it is utilized to develop compounds with potential therapeutic properties, such as anti-inflammatory and antimicrobial agents. Its role in organic synthesis also extends to the creation of complex molecules for research and industrial applications.