Rigid Scaffolds for Supramolecular Applications in Organic Media and Water

The research activity involved in this PhD project was oriented towards the development and the investigation of aromatic scaffolds for supramolecular applications in organic media and water. To do so, the investigation concerned three main topics, the first one consisting in the investigation of synthetic routes to achieve new functionalized triphenylene derivatives, focusing on the formation of C-C bond in the most hindered position in the bend of the molecule. Few examples of derivatives with similar functionalizations are present in the literature. Several amidoalkylating derivatives were tested, achieving alkylation on hexamethoxytriphenylene and on a C3-symmetric triphenylene, obtaining unprecedented compounds. The second topic was focused on micellar catalysis exploiting designer surfactants. New amphiphilic molecules were synthesized starting from a C3-symmetric triphenylene, binaphthol and β- sitosterol, by linking a hydrophilic long polyoxyethylene chain. The aggregation behavior of these three new classes of surfactants was investigated by 1H NMR. The application to catalysis in aqueous media was studied. In particular, surfactants obtained from triphenylene and β-sitosterol allowed to achieve promising results in cross-coupling reactions in water, competing with commercial alternatives. Various surfactants based on BINOL and its derivatives were employed in asymmetric catalysis. Despite the good yields obtained, low asymmetric induction was detected and more tests are required to explore the effect of different combinations of surfactants and catalysts. The third topic concerned the exploration of the reactivity promoted by the hexameric resorcin[4]arene capsule in organic solvents. In particular, elimination and isomerization reactions of substrate such as (S)-citronellal, 1,1-diphenylethanol and α- and β-pinene were extensively studied. Control experiments assessed that the investigated reactions occurred or proceeded faster only in the presence of the sole resorcin[4]arene capsule, which possesses an accessible cavity which resembles the enzyme active site. To further expand the potentiality of such system, oligomerization reactions of styrene derivatives were investigated during a six months internship at the University of Basel, under the supervision of Prof. K. Tiefenbacher. Intriguing results were obtained, in particular with 4-MeO-Styrene, achieving an unprecedented trisubstituted alkene product, that it is not obtainable with traditional synthetic routes. This system allowed selective products formation, without any strong acid or metal catalysts, proving to be an effective organocatalyst, allowing a forward step toward enzyme mimics.