Cross-coupling reactions are a type of chemical reaction that allows the formation of carbon-carbon bonds by combining two different organic molecules. These reactions typically involve a metal catalyst, such as palladium or nickel, which facilitates the joining of the two reactants. This process is essential in organic synthesis, enabling the creation of complex molecules used in pharmaceuticals and materials science. One of the most well-known cross-coupling reactions is the Suzuki reaction, where an aryl or vinyl boronic acid reacts with an organic halide. Other examples include the Heck reaction and the Stille reaction. These methods have revolutionized synthetic chemistry by providing efficient pathways to construct diverse organic compounds.