Polyssena Renzi

Achieving high molecular complexity can be not trivial, but the exploitation of domino reactions provides an atom‐ and step‐economical method to reach this target. Over the past decades, a lot of efforts have been put on the development of photocatalytic cascades employing both metal‐based and purely organic catalysts. Despite the effectiveness of these protocols, catalyst‐ and additive‐free light‐induced domino reactions are gaining momentum thank to their efficiency, operational simplicity and sustainability. The increasing number of papers published on this field in the last years is a proof of the appeal of these transformations. In this Review, we discuss domino and multicomponent reactions mediated by light with a focus on photocatalyst‐ and additive‐free processes. The most recent advances in the synthesis of complex nitrogen‐, oxygen‐, sulphur‐ and selenium‐heterocycles together with multicomponent cascades are analysed with an emphasis on both experimental and mechanistic studies.

In this study, we unveiled titanium‐based tetrapyrazinoporphyrazines as a valuable alternative to noble metals in the oxygen reduction reaction (ORR). By simply modifying the synthetic conditions, we were able to tune the ORR selectivity while showing that the introduction of substituents on the macrocycle periphery is detrimental to the ability of the complex to reduce molecular oxygen. A complete electrochemical characterization in different conditions is reported together with rotating ring‐disk electrode measurements, which assessed the possibility of selectively switching from 2‐ to a 4‐electron reduction product changing the titanium precursor amounts during the complex synthesis.