The emergence of Pd-mediated reversible oxidative addition in cross coupling, carbohalogenation and carbonylation reactions

Exploiting the reversibility of chemical processes is a long-standing tactic of organic chemists, and permeates most areas of the discipline. The notion that oxidative addition of Pd(0) to Ar-X bonds can be considered an irreversible process has been challenged, periodically, over the last 30 years. Recent examples of methodologies that harness the reversibility of oxidative addition reactions in catalytic processes have enabled access to challenging carbocyclic and heterocyclic scaffolds. This Perspective seeks to describe the development of these processes from the early proof-of-principle findings, and highlight key challenges that remain in this avenue of research. In particular, we draw attention to significant deficiencies that remain in the choice of suitable ligands and additives for these transformations. We conclude by describing how the concept of reversible oxidative addition has recently been exploited in the development of novel carbonylation reactions.