4-Chloro-7-methoxy-6-(3-morpholin-4-yl-propoxy)quinazoline hydrochloride is a key synthetic intermediate used in the preparation of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, such as Gefitinib (Iressa). It serves as a building block in pharmaceutical research and development for anticancer drugs targeting solid tumors, including non-small cell lung cancer and other EGFR-driven malignancies. The 4-chloro substituent facilitates nucleophilic aromatic substitution to introduce anilino groups, forming active inhibitors that block EGFR signaling pathways, thereby inhibiting cancer cell proliferation and promoting apoptosis. Its structural features enhance solubility and support blood-brain barrier penetration in downstream analogs, aiding treatments for brain metastases. Widely utilized in preclinical synthetic chemistry to optimize processes, evaluate purity, and scale up production of targeted therapies.