Ureas and Their Derivatives as Ligands in Transition Metal Catalysis

Ureas and related compounds represent a popular class of organocatalysts, exploiting their dual hydrogen bond donor capacity to promote reactions and enable asymmetric catalysis. The use of these compounds as ligands in transition metal catalysis has been considerably less developed, despite their ease of synthesis and versatility as ligands. However, there have been notable developments over the last 15-20 years that demonstrate the viability of ureas and closely related compounds as an attractive ligand platform for transition metal catalysis. This perspective will highlight seminal work using (thio)ureas as ancillary ligands, where they engage in non-covalent interactions with substrates in the secondary coordination sphere of transition metals, and as primary ligands, where they coordinate directly to the metal to promote catalytic reactions.