Ansgar Sehlinger

Structurally Diverse Polyamides Obtained from Monomers Derived via the Ugi Multicomponent Reaction

The combination of the Ugi four-component reaction (Ugi-4CR) with acyclic diene metathesis (ADMET) or thiol-ene polymerization led to the formation of poly-1-(alkylcarbamoyl) carboxamides, a new class of substituted polyamides with amide moieties in the polymer backbone, as well as its side chains. 10-Undecenoic acid, obtained by pyrolysis of ricinoleic acid, the main fatty acid of castor oil, was used as the key renewable building block. The use of different primary amines, as well as isonitriles (isocyanides) for the described Ugi reactions provided monomers with high structural diversity. Furthermore, the possibility of versatile post-modification of functional groups in the side chains of the corresponding polymers should be of considerable interest in materials science. The obtained monomers were polymerized by ADMET, as well as thiol-ene, chemistry and all polymers were fully characterized. Finally, ortho-nitrobenzylamide-containing polyamides obtained by this route were shown to be photoresponsive and exhibited a dramatic change of their properties upon irradiation with light.

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.

Ugi Reactions with CO2: Access to Functionalized Polyurethanes, Polycarbonates, Polyamides, and Polyhydantoins

A novel strategy for the incorporation of carbon dioxide into polymers is introduced. For this purpose, the Ugi five-component condensation (Ugi-5CC) of an alcohol, CO2 , an amine, an aldehyde, and an isocyanide is used to obtain step-growth monomers. Polymerization via thiol-ene reaction or polycondensation with diphenyl carbonate gives diversely substituted polyurethanes or alternating polyurethane-polycarbonates, respectively. Furthermore, the application of 1,12-diaminododecane and 1,6-diisocyanohexane as bifunctional components in the Ugi-5CC directly results in the corresponding polyamide bearing methyl carbamate side chains (M¯n = 19 850 g mol(-1) ). The latter polymer is further converted into the corresponding polyhydantoin in a highly straightforward fashion.

Versatile side chain modification via isocyanide-based multicomponent reactions: tuning the LCST of poly(2-oxazoline)s

Poly(2-oxazoline)s are receiving large current interest based on their potential use in biomedical applications. The development of novel methods to control the polymer side chains and to tune the polymer properties will further enhance this potential. In this contribution, the Passerini and Ugi multicomponent reactions are used to modify a random poly(2-oxazoline) copolymer of 2-ethyl-2-oxazoline (EtOx) and 2-methyl butyrate-2-oxazoline (C3-MestOx) with defined chain length and comonomer ratio. Hydrolysis of the pending methyl ester groups provided an easy access to carboxylic acid groups in the side chain, which were used for post-polymerization modification reactions via isocyanide-based multicomponent reactions (IMCRs) to simultaneously introduce various substituents. This allowed a straightforward adjustment of the properties of the random poly(2-oxazoline). Most importantly, control over the cloud point and glass transition temperatures was possible by simple variation of the components used in the multicomponent grafting approach.