Plasmonic Heating-Promoted Photothermal Synthesis of α-Cyanoacrylonitriles Over Au/h-BN Catalysts.

Plasmonic nanoparticle-involved materials play an essential role in the field of photothermal conversion. Herein, we report the application of photothermal heterogeneous catalysts consisting of gold nanoparticles decorated on defect-rich h-BN sheets (Au/h-BN) for the photocatalytic synthesis of α-cyanoacrylonitriles under mild conditions. It has been demonstrated the-NH2 groups present in the defect-rich h-BN act as the catalytically active sites, while plasmonic heating from the gold nanoparticles can drive the reaction by providing local heat. Au/h-BN catalyst can work for a broad substrate scope in the synthesis of α-cyanoacrylonitriles, and a plausible -NH2 group-involved reaction mechanism has been proposed. This work may open up new avenues in photothermal catalysis by combining plasmonic materials and catalytic sites in one system.

Anti-freezing, moisturizing, resilient and conductive organohydrogel for sensitive pressure sensors.

Conductive hydrogels have attracted significant attention in the area of wearable pressure sensors due to their mechanical flexibility, conductivity and self-healing capability. At subzero temperatures, water-based conductive hydrogels unavoidably lose their elasticity and conductivity which limits their practical usages at low temperatures. However, traditional conductive hydrogels are short of moisturizing and anti-freezing ability due to the limitation of pure water solvent, which greatly restricts their application in extreme environments. In this study, an anti-freezing and moisturizing conductive double network organohydrogel was prepared by incorporating thioctic acid (TA) with polyvinyl alcohol-borate (PVA-PB) in carbon nanotubes (CNTs) that were dispersed in water (H2O) and ethylene glycol (EG). The as-prepared PVA-B-TA-CNTs organohydrogel presented outstanding anti-freezing performance (-60 oC), long-term moisturizing property (30 days), excellent stability (400 cycles) and fascinating conductive sensitivity (S = 0.625 kPa-1). The occurrence of dynamic covalent disulfide bonds and noncovalent hydrogen bonds endow the conductive organohydrogels with brilliant remoldability and self-healing ability, which are significant for practical applications. These remarkable advantages make PVA-B-TA-CNTs organohydrogel to have enormous potential in the application of wearable and flexible pressure sensors, human-healthy monitor, and intelligence devices.

Recent Advances in Plasmon-Promoted Organic Transformations Using Silver-Based Catalysts.

Plasmonics has emerged as a promising methodology to promote chemical reactions and has become a field of intense research effort. Ag nanoparticles (NPs) as plasmonic catalysts have been extensively studied because of their remarkable optical properties. This review analyzes the emergence and development of localized surface plasmon resonance (LSPR) in organic chemistry, mainly focusing on the discovery of novel reactions with new mechanisms on Ag NPs. Initially, the basics of LSPR and LSPR-promoted photocatalytic mechanisms are illustrated. Then, the recent advances in plasmonic nanosilver-mediated photocatalysis in organic transformations are highlighted with an emphasis on the related reaction mechanisms. Finally, a proper perspective on the remaining challenges and future directions in the field of LSPR-promoted organic transformations is proposed.

Visible-Light-Promoted C2 Selective Arylation of Quinoline and Pyridine N-Oxides with Diaryliodonium Tetrafluoroborate.

A protocol of visible-light-promoted C2 selective arylation of quinoline and pyridine N-oxides, with diaryliodonium tetrafluoroborate as an arylation reagent, using eosin Y as a photocatalyst for the construction of N-heterobiaryls was presented. This methodology provided an efficient way for the synthesis of 2-aryl-substituted quinoline and pyridine N-oxides. This strategy has the following advantages: specific regioselectivity, simple operation, good functional group tolerance, and high to moderate yields under mild conditions.

Visible-Light-Mediated Anti-Regioselective Nitrone 1,3-Dipolar Cycloaddition Reaction and Synthesis of Bisindolylmethanes.

The development of photoredox reactions of 1,3-dipolar cycloaddition of nitrones with alkenes is reported. It offers an efficient synthetic method to obtain isoxazolidine derivatives under mild conditions in synthetically useful yields. The nitrones are cyclized with oxidizable styrenes and aliphatic alkenes via a polar radical crossover cycloaddition reaction through photocatalytic reaction without additives. In addition, bis(indole)methanes can also be prepared through this method.

Synthesis of Oxatricyclooctanes via Photoinduced Intramolecular Oxa-[4+2] Cycloaddition of Substituted o-Divinylbenzenes.

The photolysis of substituted o-divinylbenzenes promotes a one-step and metal-free conversion to oxatricycles at room temperature. Irradiation o-divinylbenzenes results in an pericyclic reaction to form cyclic o-quinodiemthane intermediates, which subsequently undergo intramolecular oxa-[4+2] cycloaddition to form oxacyclic derivatives.

Direct oxidation of the C(sp2)-C(sp3) bond from benzyltrimethylsilanes to phenols.

A novel pathway for direct conversion of benzylsilanes to phenols by oxidation with Na2S2O8 and oxygen is efficiently developed under mild and neutral conditions. The reaction shows good functional group tolerance to afford phenols in moderate yields. The possible mechanism is proposed based on the isotopic labeling trials.

Selective C-H trifluoromethylation of benzimidazoles through photoredox catalysis.

The protocol presented here is a new strategy for visible light induced C-H trifluoromethylation at C4 of benzimidazoles using Togni's reagent in the presence of fac-Ir(ppy)3. Its advantages are its operational simplicity, mild reaction conditions, low catalyst loading and wide substrate scope in which electron-withdrawing, electron-donating groups and different protecting groups are tolerated.

Pd(II)-Catalyzed C3-Selective Arylation of Pyridine with (Hetero)arenes.

Palladium catalyzed, nondirected C3-selective arylation of pyridines with arenes and heteroarenes in the presence of 1,10-phenanthroline as the ligand has been developed. The optimized conditions allow for a highly C3-selective arylation of pyridines, affording various 3,3'-bipyridines and 3-arylpyridines.

Visible-Light-Mediated 1,7-Enyne Bicyclizations for Synthesis of Cyclopenta[c]quinolines and Benzo[j]phenanthridines.

A photocatalytic process for 1,7-enyne bicyclizations with α-bromo diethyl malonate has been established via synergistic domino bicyclizations. This protocol provides an efficient and practical method for the synthesis of various cyclopenta[c]quinolines and benzo[j]phenanthridines under operational simplicity and mild reaction conditions.

Visible-Light Induced Trifluoromethylation of N-Arylcinnamamides for the Synthesis of CF3-Containing 3,4-Disubstituted Dihydroquinolinones and 1-Azaspiro[4.5]decanes.

The visible-light induced trifluoromethylation of N-arylcinnamamides with Togni's reagent has been explored. This method allows for an efficient and practical synthesis of a variety of CF3-containing dihydroquinolin-2(1H)-ones and 1-azasporo[4.5]decanes bearing various functional groups under mild conditions.

Ligand-promoted C3-selective arylation of pyridines with Pd catalysts: gram-scale synthesis of (±)-preclamol.

The first example of Pd-catalyzed, C3-selective arylation of unprotected pyridines has been developed by employing a catalytic system consisting of Pd(OAc)(2) and 1,10-phenanthroline. This protocol provides an expeditious route to an important class of 3-arylpyridines and 3-arylpiperidines frequently found in bioactive compounds. A brief synthesis of the drug molecule (±)-preclamol is also reported.

Ligand-promoted C-3 selective C-H olefination of pyridines with Pd catalysts.

Pd-catalyzed C-3 selective olefination of pyridines is developed for the first time using 1,10-phenanthroline as the ligand. This finding provides a novel disconnection for the synthesis of pyridine-containing alkaloids and drug molecules as well as a new approach for developing Pd-catalyzed C-H functionalizations of pyridines.

Unexpected domino reaction via Pd-catalyzed Sonogashira coupling of benzimidoyl chlorides with 1,6-enynes and cyclization to synthesize quinoline derivatives.

A domino reaction via palladium-catalyzed Sonogashira coupling of benzimidoyl chlorides with 1,6-enynes and then cyclization to form quinoline derivatives has been developed. The reaction conditions and the scope of the process are examined, and a plausible mechanism is proposed. The procedure is simple, rapid, and general, and the substrates are readily available.

Synthesis of isoquinoline derivatives via Ag-catalyzed cyclization of 2-alkynyl benzyl azides.

Ag-catalyzed cyclization of 2-alkynyl benzyl azides offers a novel and efficient method for the synthesis of substituted isoquinoline. The reaction proceeds smoothly in moderate to good yields and tolerates considerable functional groups. The reaction conditions and the scope of the process are examined, and a plausible mechanism is proposed.