A comprehensive review of caged phosphines: synthesis, catalytic applications, and future perspectives

Phosphines have played an important role in the rapid rise of transition metal-catalysed processes and with the possibility of fine-tuning the electronic and steric properties of these ligands, several synthesis challenges have been overcome in the past decades leading to their application in academia and industry. Caged phosphines are one such class of phosphines with the phosphorus atom at the bridgehead of a cyclic cage and have exhibited excellent control of the steric and electronic properties leading to their applications as ligands in a vast number of catalytic processes. This review provides an overview of the origin of this area of research, as well as the developments that have taken place and how the unique properties of these ligand systems could help to fine-tune the reactivity. A critical analysis of the area reveals some lacunae that will also be highlighted to promote further developments in this area of research.