A General Photoactive H-Bonding EDA Complex Model Drives the Selective Hydrothiolation and Hydroxysulfenylation of Carbonyl Activated Alkenes.

Excitation of photoactive electron donor-acceptor (EDA) complexes to generate radical is a promising approach in radical chemistry. In this study, we introduce a new model of H-bonding EDA complexes for the selective hydrothiolation and hydroxysulfenylation of carbonyl-activated alkenes with diverse thiols under visible light conditions. The reliability of this H-bonding EDA complex model has been confirmed by meticulous experimental and theoretical calculations. Mechanistic investigations have revealed the significant influence of the solvent in determining whether the excitation of photoactive H-bonding EDA complex leads to charge transfer (CT) or energy-charge transfer (En-CT), thereby controlling Markovnikov and anti-Markovnikov selectivity. Notably, the Quantum Theory of Atoms in Molecules (QTAIM) analysis clearly shows that the excited state of the C＝O---H-S EDA complex involves closed-shell partially covalent interactions.

Chemoselective Synthesis of 3-Bromomethyloxindoles via Visible-Light-Induced Radical Cascade Bromocyclization of Alkenes.

A novel visible-light-induced radical cascade bromocyclization of N-arylacrylamides has been accomplished. This reaction overcomes the overbromination at the benzene rings suffered in traditional electrophilic reactions, thus enabling the first highly chemoselective synthesis of valuable 3-bromomethyloxindoles. The combination of pyridine and anhydrous medium is identified as the key factor for the high chemoselectivity in the current photoreaction system, which might work by suppressing the in situ generation of low-concentration Br2 from N-bromosuccinimide. Moreover, the mild reaction conditions ensure the generation of a wide range of the new desired products with excellent functional group tolerance.

Base-promoted one-pot three-component desulphurization cross-coupling access to 4-cyanoimidazole.

A novel, straightforward, and scalable base-mediated one-pot three-component desulphurization cross-coupling strategy is reported for the synthesis of 4-cyanoimidazole derivatives. Over 35 examples are provided and achieved yields exceeding 85%. Notably, the majority of these readily available compounds can be isolated through simple filtration, thereby circumventing the need for laborious column chromatography. Besides, the present protocol can be scaled up to 10 mmol with a yield of 87%, demonstrating promising potential for industrial applications.

Hydrophosphorylation of electron-deficient alkenes and alkynes mediated by convergent paired electrolysis.

A straightforward and practical strategy for hydrophosphorylation of electron-deficient alkenes and alkynes to access γ-ketophosphine oxides, enabled by a convergent paired electrolysis (CPE) in the absence of a metal, base, and redox reagent, has been described. Mechanistic studies have revealed that the diarylphosphane oxides play the dual role of a phosphorus radical precursor and hydrogen donor in this transformation.

An electrochemical gram-scale protocol for pyridylation of inert N-heterocycles with cyanopyridines.

Here, we present a protocol to decyanopyridate inert N-heterocycles access to N-fused heterocycles via the mechanism of dual proton-coupled electron transfer (PCET). We describe a detailed guide to performing an electrochemical gram-scale protocol for decyanopyridation of inert N-heterocycles. The desired pyridylated quinolone is synthesized in a 5.0 mmol scale with a yield of 76%. The protocol is limited to cyanopyridines. For complete details on the use and execution of this protocol, please refer to Niu et al. (2022).

Electrochemical ammonium-cation-assisted pyridylation of inert N-heterocycles via dual-proton-coupled electron transfer.

A straightforward and practical strategy for pyridylation of inert N-heterocycles, enabled by ammonium cation and electrochemical, has been described. This protocol gives access to various N-fused heterocycles and bidentate nitrogen ligand compounds, through dual-proton-coupled electron transfer (PCET) and radical cross-coupling in the absence of exogenous metal and redox reagent. It features broad substrate scope, wide functional group tolerance, and easy gram-scale synthesis. Various experiments and density functional theory (DFT) calculation results show the mechanism of dual PCET followed by radical cross-coupling is the preferred pathway. Moreover, ammonium salt plays the dual role of protonation reagent and electrolyte in this conversion, and the resulting product 9-(pyridin-4-yl)acridine compound can be used for fluorescence recognition of Fe2+ and Pd2+ with high sensitivity.

Electroreductive C3 Pyridylation of Quinoxalin-2(1H)-ones: An Effective Way to Access Bidentate Nitrogen Ligands.

The construction of functional N-containing active biomolecules and bidentate nitrogen ligands by electroreductive pyridylation of N-heteroaromatics is an eye-catching task and challenge. A simple and practical electroreductive-induced C3 pyridylation of quinoxalin-2(1H)-ones with readily available cyanopyridines is reported. More than 36 examples are supplied, and the reaction performed in >95% yield. The present protocol provides a convenient, efficient, and gram-scale synthesis strategy for a series of new types of potential bidentate nitrogen ligands.

Electrochemical-Induced Transfer Hydrogenation of Imidazopyridines with Secondary Amine as Hydrogen Donor.

Electrochemical-induced transfer hydrogenation (TH) of N-heteroaromatic to construct biologically active functional molecule is an appealing and yet challenging task. We report herein the first selective transfer hydrogenation of imidazopyridine derivatives with secondary amines as the hydrogen donors under electrochemical conditions. The successful conversion of cathode transfer hydrogenation depends on the solvation effect. Importantly, such electrochemical-induced transfer hydrogenation can be easily amplified with excellent efficiency.

Synthesis of Substituted Naphtho[1,8-bc]thiopyrans by Sulfhydryl-Directed Rhodium-Catalyzed peri-Selective C-H Bond Activation and Cyclization of Naphthalene-1-thiols.

The sulfhydryl-directed peri-selective C-H bond activation and tandem cyclization of naphthalene-1-thiols with alkynes proceed efficiently. Most products of naphthothiopyrans with various substituents are achieved in good yields under rhodium catalysis. This protocol has some advantages over the traditional methods in synthesizing naphtho[1,8-bc]thiopyrans in terms of stable coupling substrates, simple operation, peri-selectivity, and atom and step economy.

Metal-Free Catalytic Synthesis of Thiocarbamates Using Sodium Sulfinates as the Sulfur Source.

A novel molecular iodine-catalyzed protocol for the construction of thiocarbamates from readily available sodium sulfinates, isocyanides, and water has been described. The present methodology offers a facile and practical route to a variety of thiocarbamates in moderate to good yields with favorable functional group tolerance by use odorless sodium sulfinates as the sulfur source. The mechanistic studies suggest the present transformation involves a radical process.

Low-Pressure Flow Chemistry of CuAAC Click Reaction Catalyzed by Nanoporous AuCu Membrane.

Click chemistry has been widely used in bioconjugation, polymer synthesis, and the development of new anticancer drugs. Here, we report a nanoporous membrane made of AuCu alloy nanowires, which can effectively catalyze copper(I)-catalyzed 1,3-dipolar cycloaddition between azide and terminal alkyne (CuAAC) in flow condition with pressure less than one bar. Comparison studies of the nanowires before and after the reaction using X-ray photoelectron spectroscopy reveal Cu(0) and Cu(I) are main species that promote the reaction. This simple strategy can be used to synthesize a variety of compounds with triazole linkage and extended to gram level chemical production.

Synergic TiO2 photocatalysis and guanine photoreduction for silver deposition amplification: an ultrasensitive and high-throughput visualized colorimetric analysis strategy for anthrax DNAs in blood using a wettable microwells array.

An ultrasensitive and high-throughput visualized colorimetric method has been initially developed with a wettable microwells array for probing guanine base-containing anthrax DNAs in blood based on silver deposition amplified by the synergic TiO2 photocatalysis and guanine photoreduction under visible light. Hydrophilic microwells were first created on the hydrophobic slides to yield the wettable microwells array, on which photocatalytic titanium dioxide (TiO2) nanoparticles were deposited with dopamine (DA) to yield TiO2@DA for anchoring single strand DNA (ssDNA) capture probes without guanine bases. After the hybridization of the targeted anthrax DNAs, exonuclease I (Exo I) was introduced into the microwells to selectively digest the unhybridized ssDNA probes. The silver deposition was further conducted by the synergic photocatalysis of TiO2@DA and photoreduction of guanine bases of anthrax DNAs, thus achieving the amplified silver signals for the visualized colorimetric assays. Moreover, benefitting from the wettability feature of the hydrophilic-hydrophobic interfaces of the microwells array so fabricated, DNA analytes could be accumulated from the sample droplets through the condensing enrichment process to realize the ultrasensitive detection, in addition to circumventing any crossover contaminants between the sample droplets. The developed visualized colorimetric method with the microwells array was subsequently applied for probing anthrax DNAs in blood with levels down to 1.0 fM. DNAs with single-base and double-base mutations could also be identified accurately. Importantly, such a biosensing design route of a wettable microwells array, in combination with the photocatalytic silver deposition and specific Exo I-catalytic probe digestion, may promise extensive applications for the high-throughput, ultrasensitive, and selective detection of guanine-containing DNA targets with ultra-trace levels in complicated samples like blood.

Metal-Free Direct Alkylation of Ketene Dithioacetals by Oxidative C(sp2 )-H/C(sp3 )-H Cross-Coupling.

The functionalization of internal olefins has been a challenging task in organic synthesis. This protocol provides an efficient and transition-metal-free direct oxidative C(sp2 )-H/C(sp3 )-H cross-coupling method to access tetrasubstituted olefins. The push-pull effect from the polarized olefin substrates accelerates the internal olefin C-H alkylation. Importantly, the mechanistic experimental results demonstrate that the alkanes C-H bond cleavage is the rate-determining step, and a radical pathway has been proposed for the alkylation reaction. Notably, the present protocol has excellent functional group tolerance and could be easily scaled up with good efficiency.

Electrooxidative Tandem Cyclization of Activated Alkynes with Sulfinic Acids To Access Sulfonated Indenones.

An electrooxidative direct arylsulfonlylation of ynones with sulfinic acids via a radical tandem cyclization strategy has been developed for the construction of sulfonated indenones under oxidant-free conditions. This method provides a simple and efficient approach to prepare various sulfonylindenones in good to excellent yields, demonstrating the tremendous prospect of utilizing electrocatalysis in oxidative coupling. Notably, this reaction could be easily scaled up with good efficiency.

Palladium/Copper Co-catalyzed Oxidative C-H/C-H Carbonylation of Diphenylamines: A Way To Access Acridones.

An efficient palladium/copper co-catalyzed oxidative double C(sp2)-H functionalization/carbonylation of diphenylamines for synthesis of acridones has been developed. This method utilizes readily available starting materials and mild reaction conditions. The protocol provides a simple, efficient, and atom-economic way to access acridones. Notably, the present protocol has excellent functional group tolerance and application value.

Metal-Free Oxidative Spirocyclization of Alkynes with Sulfonylhydrazides Leading to 3-Sulfonated Azaspiro[4,5]trienones.

A novel and direct oxidative spirocyclization of arylpropiolamides with sulfonylhydrazides leading to 3-sulfonated azaspiro[4,5]trienones has been developed under metal-free conditions. The reaction is performed in a tandem manner constituted by the sequential sulfonylation of alkynes, ipso-carbocyclization, dearomatization, hydration, and oxidation processes, providing a convenient and efficient approach to various sulfonated azaspiro[4,5] trienones of biological importance.

Direct and metal-free arylsulfonylation of alkynes with sulfonylhydrazides for the construction of 3-sulfonated coumarins.

A novel and metal-free procedure has been developed for the construction of 3-sulfonated coumarins via the direct difunctionalization of alkynoates with sulfonylhydrazides. The present protocol, which simply utilizes TBAI as the catalyst and TBHP as the oxidant, provides a convenient and highly efficient approach to construct a series of sulfonated coumarins with high regioselectivity and good functional group tolerance.

Iron-catalyzed direct difunctionalization of alkenes with dioxygen and sulfinic acids: a highly efficient and green approach to ß-ketosulfones.

A novel iron-catalyzed direct difunctionalization of alkenes with sulfinic acids and dioxygen for the synthesis of ß-ketosulfones has been developed under mild conditions. The present protocol, which utilizes an inexpensive iron salt as the catalyst, readily available benzenesulfinic acids as the sulfonylating reagents, and dioxygen as the oxidant and oxygen source, provides a cost-effective and environmentally benign approach to access various ß-ketosulfones.

High-throughput colorimetric assays for mercury(II) in blood and wastewater based on the mercury-stimulated catalytic activity of small silver nanoparticles in a temperature-switchable gelatin matrix.

A catalysis-based, label-free, and high-throughput colorimetric protocol has been initially proposed for detecting mercury(II) in blood and wastewater with 96-cell plates, based on the mercury-enhanced catalytic activity of small silver nanoparticles synthesized in a gelatin matrix with unique temperature switchable sol-gel transition.

Metal-free direct trifluoromethylation of activated alkenes with Langlois' reagent leading to CF3-containing oxindoles.

A metal-free and cost-effective synthesis protocol has been initially proposed for the construction of CF3-containing oxindoles via the direct oxidative trifluoromethylation of activated alkenes with Langlois' reagent (CF3SO2Na). The present methodology, which utilizes very cheap CF3 reagent and a simple oxidant, provides a convenient and practical approach to CF3-containing oxindoles with a wide variety of functional groups.