4-Cyanobutylzinc bromide is primarily utilized in organic synthesis as a versatile organozinc reagent. It is commonly employed in carbon-carbon bond-forming reactions, such as Negishi coupling, where it acts as a nucleophile to react with various electrophiles like aryl or vinyl halides. This reagent is particularly useful in the synthesis of complex organic molecules, including pharmaceuticals and fine chemicals, due to its ability to introduce the 4-cyanobutyl group into target structures. Its stability and reactivity under mild conditions make it a valuable tool in the development of novel compounds in medicinal chemistry and materials science.