Used primarily as an intermediate in the synthesis of fluorescent dyes and labeling reagents for biomolecules. It readily reacts with nucleophiles such as amines and thiols, making it suitable for modifying proteins, peptides, and nucleic acids in biochemical assays. Commonly employed in the preparation of fluorescent probes for detecting and quantifying biomolecules in imaging and diagnostic applications. Also utilized in the development of kinase inhibitors and other pharmaceutical agents due to its quinazoline core, which is known for biological activity in drug discovery. Its nitro and chloro groups allow for sequential functionalization, enabling stepwise construction of complex molecules in medicinal chemistry.