ABSTRACT
The urea functional group contains both hydrogen bond donors and a hydrogen bond acceptor and readily forms directional intermolecular interactions. Thus, it is no surprise that this easily synthesized functional group has become a standard moiety for supramolecular chemists. This entry focuses on the use of urea‐containing building blocks that have a high propensity to assemble into dimers with an inner cavity. These capsules can completely engulf a guest, trapping it in their interior. Urea capsules can act as nanoreactors to facilitate reactions such as the Diels–Alder reaction of cyclohexadiene and p‐benzoquinone. Many groups have capitalized on the supramolecular association of these simple monomers to create intricate molecular architectures including catenanes, rotaxanes, dendrimers, and linear polymers.
