This review summarizes recent developments in photocatalyzed carbon–sulfur bond formation. General concepts, synthetic strategies and the substrate scope of reactions yielding thiols, disulfides, sulfoxides, sulfones and other organosulfur compounds are discussed together with the proposed mechanistic pathways.

The direct C−H/N−H dehydrogenative cross‐coupling of NH‐sulfoximines with electron‐rich arenes was realized by oxidative visible‐light photoredox catalysis, applying 9‐mesityl‐10‐methylacridinium perchlorate as an organic photocatalyst. Sulfoximines display diverse desirable properties for medicinal chemistry and the pharmaceutical industry. However, their preparation is still challenging. Our reaction proceeds without sacrificial oxidant, at room temperature and is highly selective for the C−N bond forming reaction. The scope of the reaction includes mono‐ and multi‐alkylated and halogenated arenes, which are reacted with aromatic and aliphatic electron‐rich and electron‐poor NH‐sulfoximines, giving moderate to excellent yields of the N‐arylated sulfoximines. In addition, we successfully conducted the developed reaction on a gram scale (1.5 g). Mechanistic investigations show that both arene and NH‐sulfoximine interact with the excited‐state of the photocatalyst. We propose a radical‐based mechanism, where both the arene and the NH‐sulfoximine are photo‐oxidized to their respective radical intermediates. Radical‐radical cross‐coupling subsequently leads to the N‐arylated sulfoximine. Two electrons and two protons are released during the reaction and are subsequently converted into H2 by a proton‐reducing cobalt‐catalyst.

A broad computational analysis of carboncentered radical formation via the loss of either CO 2 or SO 2 from the respective RXO 2 radical precursors (X = C or S) reveals dramatic differences between these two types of dissociative processes. Whereas the C−C scission with the loss of CO 2 is usually exothermic, the C−S scission with the loss of SO 2 is generally endothermic. However, two factors can make the C−S scissions thermodynamically favorable: increased entropy, characteristic for the dissociative processes, and stereoelectronic influences of substituents. The threshold between endergonic and exergonic C−S fragmentations depends on subtle structural effects. In particular, the degree of fluorination in a radical precursor has a notable impact on the reaction outcome. This study aims to demystify the intricacies in reactivity regarding the generation of radicals from sulfinates and carboxylates, as related to their role in radical cross-coupling.

Heteroaromatic sulfoxides are a frequent structural motif in natural products, drugs, catalysts, and materials. We report a metal-free visible-light-accelerated synthesis of heteroaromatic sulfoxides from sulfinamides and peroxodisulfate. The reaction proceeds at room temperature with blue-light irradiation and allows the C-H sulfinylation of electron-rich heteroarenes, such as pyrroles and indoles. An electrophilic aromatic substitution mechanism is proposed based on the substrate scope, substitution selectivity, and competition experiments with different nucleophiles.

The dual catalytic arylation of aromatic aldehydes by aryl bromides using UV-irradiation and a nickel catalyst is reported.