Used as a key intermediate in the synthesis of biologically active compounds, particularly in pharmaceuticals and agrochemicals. Its sulfonyl chloride group readily reacts with amines and alcohols, making it valuable for introducing the isoquinoline moiety into larger molecules. Commonly employed in the development of kinase inhibitors and other medicinal agents targeting cancer and inflammatory diseases. Also utilized in research settings for labeling and derivatization of biomolecules due to its reactive functionality and aromatic stability.