This review offers an overview of recent synthetic strategies employing photoredox catalysis and electrochemistry in the framework of multicomponent reactions.

Despite their prevalence in organic synthesis, the application of boronic acids (BAs) as alkyl radical precursors in visible-light-assisted photocatalyzed reactions has been limited by their high oxidation potential. This study demonstrates the prominent ability of amide solvents, namely, N,N-dimethylacetamide, to participate in hydrogen-bonding interactions with BAs, thus enabling the modulation of their oxidation potential toward the generation of alkyl radicals. The developed protocol is simple and robust and demonstrates broad applicability for alkylation, allylation, and elimination reactions in batch and continuous flow. The application toward dehydroalanine allows the synthesis of unnatural amino acids. Furthermore, the chemoselective generation of radical species from BAs in the presence of boronic ester-containing molecules is now feasible, endorsing plausible boron-selective (bio-) orthogonal modifications.

Summary Multicomponent reactions (MCRs) are ideal platforms for the generation of a wide variety of organic scaffolds in a convergent and atom-economical manner. Many strategies for the generation of highly substituted and diverse structures have been developed and among these, the Petasis reaction represents a viable reaction manifold for the synthesis of substituted amines via coupling of an amine, an aldehyde and a boronic acid (BA). Despite its synthetic utility, the inherent drawbacks associated with the traditional two-electron Petasis reaction have stimulated continuous research towards more facile and tolerant methodologies. In this regard, we present the use of free alkyl BAs as effective radical precursors in this MCR through a single-electron transfer mechanism under mild reaction conditions. We have further demonstrated its applicability to photo-flow reactors, facilitating the reaction scale-up for the rapid assembly of complex molecular structures.

The development of methods for deuterium incorporation has gained increased attention owing to the importance of deuterated molecules in chemical, medicinal and biological sciences. Despite a number of procedures reported...

The chemistry of boron compounds has been profoundly investigated in the last decades, leading to ubiquity in many synthetic applications as well as biologically active molecules. Since the advent of photoredox catalysis, an upsurge in the discovery of suitable radical precursors has been witnessed, and boron is becoming a protagonist in this field. Despite many studies focused on trifluoroborates, the use of boronic acids and esters have received much less attention in this regard. Because of their high oxidation potential, the development of methods to enable their involvement in photocatalyzed reactions is only recent. Nonetheless, this review summarizes novel strategies developed to unlock their role as radical precursors in photochemical reactions and discloses the potential that boronic acids and esters own, when their intrinsic chemical properties are exploited.