METHODOLOGIES FOR THE SYNTHESIS OF THIAHELICENE-BASED PHOSPHORUS DERIVATIVES AND THEIR APPLICATIONS IN ASYMMETRIC CATALYSIS

Helicenes are ortho-annulated polycyclic aromatic or heteroaromatic compounds endowed with inherent chirality due to the helical shape of their π-conjugated system, whose unique structural features and physicochemical properties have stimulated countless studies in several fields, including nanosciences, chemosensing, materials science, biomolecular recognition, and asymmetric catalysis. However, whilst axial, central and planar chirality have been largely exploited to build chiral phosphorus ligands and organocatalysts, helical chirality has been rather neglected so far in this field. This Ph.D. thesis aims to provide a meaningful contribution in the development of heterohelicene phosphorus derivatives, especially thiahelicene derivatives, as innovative chiral ligands to use in asymmetric organic and organometallic catalysis. In particular, we set up new classes of tetrathiahelicene(7-TH)-based phosphorus derivatives, including phoshine-borane complexes, phosphine oxides, free phosphanes, phosphathiahelicenes and the corresponding gold (I) complexes. Some of these systems have shown high efficiency as organocatalysts, as well as Au(I) complexes based on chiral phosphathiahelicene ligands were found to be efficient and selective catalysts in some challenging cycloisomerization reactions (ee up to 96%). The promising results obtained in this work will stimulate further developments and applications of these and analogous ligands to new asymmetric processes.