New annulation strategiesFrom polycyclic aromatic hydrocarbons to natural products

Resumen

This PhD covers three fields of synthetic organic chemistry devoted to the synthesis of new materials based on polycyclic aromatic hydrocarbons (PAHs), the development of new metal-catalyzed synthetic methodology, and the synthesis of natural product derivatives. The development of new strategies for the precise synthesis of structurally well-defined novel graphene cutouts is a field of great interest due to their potential implementation in molecular electronic devices. Particularly interesting PAHs are disc-shaped fragments of graphene because of their unique optoelectronic and self-assembly properties, which are predicted to be enhanced for expanded systems. In this context, an efficient synthesis of a new discotic highly symmetric C54H20 graphene fragment – tetrabenzocircumpyrene – was developed and the electronic properties of this new graphene fragment were examined by scanning tunneling microscopy (STM). Acenes consist of planar sets of linearly fused benzene rings and represent another appealing class of PAHs due to their semiconducting properties. Nonetheless, their applicability in electronic devices is limited by their poor solubility and their inherent instability. One approach to circumvent these limitations is the preparation of more stable partially saturated derivatives, which can be used as precursors of the conjugated systems. Thus, a selective method for the preparation of partially saturated acenes under mild reaction conditions was developed based on a gold(I)-catalyzed cyclization of suitable 1,7-enynes that were assembled from a common precursor. The method proved to be general and allowed the preparation of functionalized dihydrotetracenes, as well as larger hydroacenes with up to nine linearly fused rings. The outstanding ability of gold(I) complexes to construct complex polycyclic frameworks was also examined in the context of the synthesis of natural products. Thus, the gold(I)-catalyzed alkoxycyclization of cyclopropyl-tethered 1,6-enynes allowed the ready assembly of the [3,5,5,7] tetracyclic skeleton of Echinopines, which opened an entry for the preparation of functionalized derivatives of these natural products.