Passerini and Ugi Multicomponent Reactions in Polymer Science

Multicomponent reactions (MCRs) include more than two starting materials and are characterized by highly atom-efficient and straightforward practical procedures. Some of the most important MCRs in organic chemistry are the isocyanide-based MCRs, namely the Passerini three-component and Ugi four-component reaction. These reactions are, for example, often applied in combinatorial and medicinal chemistry due to their easy access to diversity or for the creation of complex structural motifs in the total synthesis of natural products. Only recently, they also gained great interest in macromolecular chemistry, since the variation of the single components displays an easy tool to adjust the properties of the polymers and facile introduction of functional groups is enabled. Hereby, tailor-made high-performance and smart materials can be obtained, which are currently highly requested for many applications. In order to attain this objective, several strategies are followed: the MCRs are used to synthesize structurally diverse monomers for subsequent polymerization, or by the use of bifunctional components, these reactions are directly utilized as polymerization method. Moreover, the Passerini and Ugi reaction are applied in macromolecular engineering as conjugation method of two kinds of polymers, or as tool for grafting reactions as well as in the creation of defined primary structures. Finally, these valuable reactions are also used in the convergent and divergent synthesis of dendritic architectures.