Electrochemical Deaminative Carboxylation of Aryltriazenes with CO2 to Aryl Carboxylic Acids

The utilization of CO2 as an appealing chemical feedstock for diverse synthetically valuable products is constantly evolving, potentially alleviating chemical production that relies on petrochemistry. Herein we report the first example of the electrochemical deaminative carboxylation of aryltriazenes with CO2. The reaction can be performed under mild and catalyst-free conditions by using sustainable methods with CO2 as a green C1 building block, efficiently converting a diverse range of readily available aryltriazenes into synthetically valuable carboxylic acids. In particular, the formation of C-C bonds by deaminative carboxylation would be an impactful addition to the synthesis toolbox.

The Strategies Towards Electrochemical Generation of Aryl Radicals

The advancement in electrochemical techniques has unlocked a new path for achieving unprecedented oxidations and reductions of aryl radical precursors in a controlled and selective manner. This approach facilitates the construction of aromatic carbon-carbon and carbon-heteroatom bonds. In light of the green merits and the growing importance of this technique in aryl radical chemistry, this review aims to provide an overview of the recent advance in the electrochemical generation of aryl radicals organized by the aryl radical precursor type, with a focus on the substrate scope, limitation, and underlying mechanism, thereby inspiring future work on electrochemical aryl radical generation.

Nucleophilic Aromatic Substitution of Heteroaryl Halides with Thiols

The nucleophilic aromatic substitution (SNAr) between heteroaryl halides (Cl, Br) and thiols proceeds smoothly in DMAc under the action of K2CO3 at rt-100 °C. For most electron-deficient heteroarenes, reaction takes place without introducing an additional electron-withdrawing group. For electron-rich heteroarenes, an additional electron-withdrawing group such as a simple ester, keto, cyano, and nitro group is required to ensure the reaction completes. The reactivity trend of heteroaryl halides is highly dependent on the electronic nature of the heteroarenes and orientation of halogens. Besides thiols, a couple of functionalized thioureas and thioamides are compatible with these conditions, providing the corresponding heteroaryl thioethers in good yields.

Arylazo sulfones: multifaceted photochemical reagents and beyond

The photochemical action of arylazo sulfones under visible light irradiation has recently gained considerable attention for the construction of carbon-carbon and carbon-heteroatom bonds in organic synthesis. The inherent dyedauxiliary group (-N2SO2R) embedded in the reagent is responsible for the absorption of visible light even in the absence of a photocatalyst, additive or oxidant, leading to the generation of three different radicals, viz. aryl (carbon-centred), sulfonyl (sulphur-centred) and diazenyl (nitrogen-centred) radicals, under different reaction conditions. Encountering a reagent with such a versatile behaviour is quite rare, which makes arylazo sulfones a highly interesting class of compounds. The mild reaction conditions under which these reagents can operate are an added advantage. Recently, they are also being used as non-ionic photoacid generators (PAGs), electron acceptors, and hydrogen atom transfer (HAT) and imination reagents in a number of synthetic transformations. They have displayed substantial damaging effect on the structure of DNA in the presence of light which can lead to their use as phototoxic pharmaceuticals for cancer treatment. Moreover, their photochemistry is also being exploited in polymerization reactions (as photoinitiators) and in materials chemistry (surface modification).

Nickel-Catalyzed Cross-Coupling Reaction of Aryl Methyl Sulfides with Aryl Bromides

A nickel-catalyzed cross-coupling reaction of aryl methyl sulfides with aryl bromides has been developed to access biaryls in yields of up to 86%. The reactions proceeded well using Ni(COD)2 as catalyst with the ligand BINAP (2,2'-bis(diphenylphosphanyl)-1,1'-binaphthalene) in the presence of magnesium. The method has a broad scope of substrates and is scalable. The wide availability of commercially available aryl bromides and the absence of preparation and preparation of organometallic reagents make the reaction of high application value.

Transition Metal-Free Aromatic C-H, C-N, C-S and C-O Borylation

Aromatic organoboron compounds are highly valuable building blocks in organic chemistry. They were mainly synthesized through aromatic C-H and C-Het borylation, in which transition metal-catalysis dominate. In the past decade, with increasing attention to sustainable chemistry, numerous transition metal-free C-H and C-Het borylation transformations have been developed and emerged as efficient methods towards the synthesis of aromatic organoboron compounds. This account mainly focuses on recent advances in transition metal-free aromatic C-H, C-N, C-S, and C-O borylation transformations and provides insights to where further developments are required.

Device for automated screening of irradiation wavelength and intensity – investigation of the wavelength dependence of photoreactions with an arylazo sulfone in continuous flow

A system allowing the automatic change of LED arrays (normalized to the number of emitted photons) is presented to study photochemical reactions in continuous flow for their wavelength dependence.

The organocatalytic synthesis of perfluorophenylsulfides via the thiolation of trimethyl(perfluorophenyl)silanes and thiosulfonates

The organic superbase t-Bu-P₄-catalyzed direct thiolation of trimethyl(perfluorophenyl)silanes and thiosulfonates was developed. Yields of perfluorophenylsulfides of up to 97% under catalysis of 5 mol% t-Bu-P₄ were achieved. This method was shown to provide an efficient way to construct the perfluorophenyl-sulfur bond under mild metal-free reaction conditions.

Desulfonylation via Radical Process: Recent Developments in Organic Synthesis

As the "chemical chameleon", sulfonyl-containing compounds and their variants have been merged with various types of reactions for the efficient construction of diverse molecular architectures by taking advantage of their incredible reactive flexibility. Currently, their involvement in radical transformations, in which the sulfonyl group typically acts as a leaving group via selective C-S, N-S, O-S, S-S, and Se-S bond cleavage/functionalization, has facilitated new bond formation strategies which are complementary to classical two-electron cross-couplings via organometallic or ionic intermediates. Considering the great influence and synthetic potential of these novel avenues, we summarize recent advances in this rapidly expanding area by discussing the reaction designs, substrate scopes, mechanistic studies, and their limitations, outlining the state-of-the-art processes involved in radical-mediated desulfonylation and related transformations. With a specific emphasis on their synthetic applications, we believe this review will be useful for medicinal and synthetic organic chemists who are interested in radical chemistry and radical-mediated desulfonylation in particular.