Aryl diazonium salts are versatile building blocks in organic synthesis In light of the ever-increasing importance of aryl diazonium salts spanning most disciplines of the chemical sciences, we review the recent development of aryl diazonium chemistry over the past seven years (2013-2020) Special emphasis is put on various new transformations involving the generation of radical intermediates via thermal, photochemical, and electrochemical means Recent advances in the development of transition metal-catalyzed reactions using aryl diazonium salts are also reviewed Together, these newly developed transformations significantly expand the synthetic chemist's repertoire of aromatic carbon-carbon and carbon-heteroatom bond forming methods using aryl diazonium precursors, providing powerful tools for the synthesis and modification of complex molecular scaffolds

Recent Development of Aryl Diazonium Chemistry for the Derivatization of Aromatic Compounds

Sulfonyl compounds have attracted considerable interest due to their extensive applications in drug discovery. Access to the assembly of SO2-containing compounds via the oxygenation oxidative-state introduction of hypervalent sulfur has come to the fore in recent years. This review discusses the application of the same oxygenation-state introduction of hypervalent sulfur strategy under transition-metal-free conditions, and presents it in light of different atoms being linked to the sulfonyl group, including sulfones, sulfonamides, sulfonyl fluorides and thiosulfonates.

https://pubs.rsc.org/en/content/articlepdf/2020/QO/D0QO00987C

The same oxygenation-state introduction of hypervalent sulfur under transition-metal-free conditions

Sulfonyl fluorides have widespread applications in many fields. In particular, their unique biological activity has drawn considerable research interest in the context of chemical biology and drug discovery in the past years. Therefore, new and efficient methods for the synthesis of sulfonyl fluorides are highly in demand. In contrast to extensive studies on FSO2 + -type reagents, a radical fluorosulfonylation reaction with a fluorosulfonyl radical (FSO2 . ) remains elusive so far, probably owing to its instability and difficulty in generation. Herein, the development of the first radical fluorosulfonylation of alkenes based on FSO2 radicals generated under photoredox conditions is reported. This radical approach provides a new and general access to alkenyl sulfonyl fluorides, including structures that would otherwise be challenging to synthesize with previously established cross-coupling methods. Moreover, extension to the late-stage fluorosulfonylation of natural products is also demonstrated.

Radical Fluorosulfonylation: Accessing Alkenyl Sulfonyl Fluorides from Alkenes

Photoredox-catalyzed sulfonylation of difluoroenoxysilanes with the insertion of sulfur dioxide.

Visible-light photoredox catalysis has been regarded as an extremely powerful tool in organic chemistry, bringing the spotlight back to radical processes. The versatility of photocatalyzed reactions has already been demonstrated to be effective in providing alternative routes for cross-coupling as well as multicomponent reactions. The photocatalyst allows the generation of high-energy intermediates through light irradiation rather than using highly reactive reagents or harsh reaction conditions. In a similar vein, organic electrochemistry has experienced a fruitful renaissance as a tool for generating reactive intermediates without the need for any catalyst. Such milder approaches pose the basis toward higher selectivity and broader applicability. In photocatalyzed and electrochemical multicomponent reactions, the generation of the radical species acts as a starter of the cascade of events. This allows for diverse reactivity and the use of reagents is usually not covered by classical methods. Owing to the availability of cheaper and more standardized photo- and electrochemical reactors, as well as easily scalable flow-setups, it is not surprising that these two fields have become areas of increased research interest. Keeping these in view, this review is aimed at providing an overview of the synthetic approaches in the design of MCRs involving photoredox catalysis and/or electrochemical activation as a crucial step with particular focus on the choice of the difunctionalized reagent.

/pdf/multicomponent-reactions-and-photo-electrochemistry-join-hzx9ufru.pdf

Multicomponent reactions and photo/electrochemistry join forces: atom economy meets energy efficiency.

Copper-free Sandmeyer-type Reaction for the Synthesis of Sulfonyl Fluorides

Recent progress in the synthesis of sulfonyl fluorides for SuFEx click chemistry

The development of efficient approaches to access sulfonyl fluorides is of great significance because of the widespread applications of these structural motifs in many areas, among which the emerging sulfur(vi) fluoride exchange (SuFEx) click chemistry is the most prominent. Here, we report the first three-component aminofluorosulfonylation of unactivated olefins by merging photoredox-catalyzed proton-coupled electron transfer (PCET) activation with radical relay processes. Various aliphatic sulfonyl fluorides featuring a privileged 5-membered heterocyclic core have been efficiently afforded under mild conditions with good functional group tolerance. The synthetic potential of the sulfonyl fluoride products has been examined by diverse transformations including SuFEx reactions and transition metal-catalyzed cross-coupling reactions. Mechanistic studies demonstrate that amidyl radicals, alkyl radicals and sulfonyl radicals are involved in this difunctionalization transformation.

/pdf/photoredox-catalyzed-aminofluorosulfonylation-of-unactivated-25sug0je1m.pdf

Tao Zhong

Papers

Copper-free Sandmeyer-type Reaction for the Synthesis of Sulfonyl Fluorides

Recent progress in the synthesis of sulfonyl fluorides for SuFEx click chemistry

Photoredox-catalyzed aminofluorosulfonylation of unactivated olefins.

Deformation twinning in single-crystal Mg under high strain rate tensile loading: A time-resolved X-ray diffraction study