Visible - light - promoted dearomative cyclizations: new routes to complex polycycles

Visible - light - promoted dearomative cyclizations are an extremely useful tool for increasing the molecular complexity of a product, starting from cheap, abundant, and commercially available aromatic reagents. However, the reluctance of the arene to break its aromaticity limits the applicability of these transformations. Indeed, harsh conditions are often necessary, resulting in low yields and selectivity. In this thesis, 4 examples of dearomatizing cyclizations will be reported. They are all characterized by the use of very mild conditions, resulting in broad tolerance towards functional groups and excellent selectivity. We were able to achieve the 1,4-para-cycloaddition on simple aromatics in an intramolecular fashion and, with naphthalenes, intramolecularly. We also successfully dearomatized simple- and benzoheteroaromatics with two strategies: a [2+2] cycloaddition with cinnamyls, and a skeletal rearrangement that bring to a fused polycycle starting from enallenes. All these transformations have complete atom economy and employ a cheap setup, that can be adopted in every synthetic laboratory.