Ethyl 4-isocyanatobenzoate is primarily used as a reactive intermediate in organic synthesis, particularly in the production of polymers and specialty chemicals. Its isocyanate group enables it to participate in reactions with compounds containing active hydrogen atoms, such as alcohols and amines, forming urethanes or ureas. This property makes it valuable in the development of coatings, adhesives, and elastomers, where it enhances durability and chemical resistance. Additionally, it is utilized in the synthesis of pharmaceutical compounds, contributing to the creation of active pharmaceutical ingredients (APIs) with specific functional properties. Its role in cross-linking reactions also makes it suitable for modifying materials to achieve desired mechanical and thermal characteristics.