Bouthayna Zilate

Owing to their favorable molecular topology, atropisomers represent particularly valuable chiral scaffolds for numerous applications throughout academic research and industry. Nevertheless, whereas various well-established catalyst-controlled methodologies allow addressing stereocenter configuration, efficient procedures to prepare axially chiral compounds in high isomeric purity are still scarce. Complementary to the comprehensive reviews in the area, this Perspective features representative advances for the catalyst-stereocontrolled synthesis of atropisomeric scaffolds. With a focus on axially chiral motifs frequently utilized in catalysis or medicinal chemistry, selected recent examples encompassing unique stereoselective transition metal, hydrogen bond, ion pairing, chiral phosphoric acid, and amine catalysis are highlighted.

Recent developments in preparative photocatalysis have reshaped synthetic strategies and now represent an integral part of current organic chemistry. Due to their favourable electrochemical and photophysical properties, the nowadays most frequently used photocatalysts are based on precious Ru- and Ir-polypyridyl complexes. Apart from that, organic catalysts such as the acridinium salts are now commonly employed to complement transition metals to provide potentially sustainable strategies amenable to large-scale synthesis. In this feature article, the design, synthesis and application of aminoacridinium photoredox catalysts as well as their exceptionally broad range of redox properties are highlighted. Due to their modularity, this burgeoning class of organophotocatalysts is anticipated to contribute significantly to synthetic methodology development and the translation to a wide range of innovative implementations.

Control over redox states and spin multiplicity of photocatalysts throughout a catalytic cycle is crucial for selective and efficient photocatalytic processes. However, the rational design of photocatalysts is often hampered by the mechanistic complexity and low modularity of the catalyst structure. Herein, we demonstrate a photophysical study of diverging photocatalytic pathways that guides the design of organic acridinium catalysts to complement polypyridyl transition metal systems. A combined halogen–metal exchange/directed ortho-metalation provides reagents for a broad range of modular acridinium catalysts with fine-tuned photophysical and photochemical properties such as excited-state lifetimes, redox potentials, and photostabilities poised to refine organocatalytic photoredox methodology.

The continuous development of photocatalytic methods incentivizes the design of organic catalysts to complement the frequently used and precious polypyridyl transition metal systems. Herein, a scalable synthesis of suitable acridinium dyes and their application in photoredox deuterations are described. The acridinium catalysts, prepared on multi-gram scale, allowed the deuteration of a pharmaceutically relevant scaffold in high yield and selectivity under mild conditions.

Abstract Photostability is an essential design aspect for the overall performance of photocatalysts, particularly as groups introduced to adjust redox properties often constitute sites of potential reactivity. Herein, we describe a modular and flexible synthetic approach to incorporate diarylamino moieties with increased photostability that allow to efficiently tune the redox behavior of a new generation of organic acridinium photocatalysts. A series of cross‐coupling reactions gave access to precursors for halogen metal exchange reactions combined with directed ortho ‐metalations to provide reagents that allow the formation of acridinium salts with adjustable redox properties and enhanced photostability in good yields. magnified image