Jacopo Scarfiello

The conversion of carbon dioxide into value-added products has emerged as an alternative method to achieve net-zero emissions. While technologies that transform CO2 into fuels and chemical feedstocks have made great strides, the direct use of CO2 as C1 synthon for the formation of new carbon-carbon bonds remains a critical challenge. Herein, we present a new catalytic CO2 activation mode for hydrocarboxylation reactions. Key to this methodology is the formation of a CO2 carbamate with a phenothiazine catalyst, which sets the required trigonal geometry for the release of CO2•− via photolysis upon absorption of visible light. The polarity-reversed CO2•− is employed in hydrocarboxylation reactions of alkenes and heterocycles. This protocol is distinguished by its wide substrate scope and broad applicability, even in the context of pharmaceutical cores. Our chemistry can also be utilized for the synthesis of carbon-13 labeled spirolactones using 13CO2. Mechanistic experiments support the photolysis of CO2 carbamate as the main productive pathway under our optimized reaction conditions.

This review provides an overview of skipped dienes synthesis in the last five years. Metal-mediated, metal-free, synergistic/dual and metallaphotoredox catalysed reactions are analysed based on catalytic system, mechanism and stereoselectivity.

A mild and catalyst‐free protocol to obtain several 2‐chloromethylpyrrolidines by the use of a commercial solution of sodium hypochlorite is here reported, without the need for a light source. The choice of the solvent revealed to be crucial in the success of the reaction. Mechanistic studies, both experimental and computational, confirmed a radical mechanism, where the deprotonation step, followed by the oxidation of a N‐centered anion to the corresponding radical, allowed 2‐chloromethylpyrrolidines, by a very fast cyclization, to be obtained. Sodium hypochlorite plays the role of both the oxidant and the chlorine source.

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.