The Heck reaction proceeds through several key steps:
Oxidative addition of the aryl halide to the palladium catalyst, forming a palladium-aryl complex. Coordination of the alkene to the palladium center, followed by migratory insertion of the alkene into the palladium-aryl bond. β-Hydride elimination to form the product and regenerate the palladium catalyst. Reductive elimination to release the product and restore the active form of the catalyst.
