4-Phenylbut-3-enoic acid is primarily utilized in organic synthesis as a versatile intermediate for the production of various pharmaceuticals and fine chemicals. Its structure, featuring both a phenyl group and a carboxylic acid, makes it valuable for constructing complex molecules. It is often employed in the synthesis of anti-inflammatory drugs, analgesics, and other bioactive compounds. Additionally, it serves as a precursor in the development of liquid crystals and polymers, where its conjugated system can enhance material properties. In research, it is used to study reaction mechanisms and develop new synthetic methodologies.