More than Bystanders: The Effect of Olefins on Transition-Metal-Catalyzed Cross-Coupling Reactions

Olefins and alkynes are ubiquitous in transition‐metal catalysis, whether introduced by the substrate, the catalyst, or as an additive. Whereas the impact of metals and ligands is relatively well understood, the effects of olefins in these reactions are generally underappreciated, even though numerous examples of olefins influencing the outcome of a reaction, through increased activity, stability, or selectivity, have been reported. This Review provides an overview of the interaction of olefins with transition metals and documents examples of olefins influencing the outcome of catalytic reactions, in particular cross‐coupling reactions. It should thus provide a basis for the improved understanding and further utilization of olefin and alkyne effects in transition‐metal‐catalyzed reactions. Olé to olefins: Olefins as components of transition‐metal‐catalyzed reactions can influence the outcome of a reaction through increased activity, stability, or selectivity. This Review outlines the interaction of olefins with transition metals and documents examples of olefins that influence catalytic reactions; a particular focus is on cross‐coupling reactions.