Photoinduced C-C Cross-Coupling of Aryl Chlorides and Inert Arenes

Here we report a facile, efficient, and catalyst-free method to realize C-C cross-coupling of aryl chlorides and inert arenes under UV light irradiation. The aryl radical upon homolytic cleavage of C-Cl bond initiated the nucleophilic substitution reaction with inert arenes to give biaryl products. This mild reaction mode can also be applied to other synthetic reactions, such as the construction of C-N bonds and trifluoromethylated compounds

Mechanistic study of visible light-driven CdS or g-C₃N₄-catalyzed C–H direct trifluoromethylation of (hetero)arenes using CF₃SO₂Na as the trifluoromethyl source

The mild and sustainable methods for C–H direct trifluoromethylation of (hetero)arenes without any base or strong oxidants are in extremely high demand. Here, we report that the photo-generated electron-hole pairs of classical semiconductors (CdS or g-C3N4) under visible light excitation are effective to drive C–H trifluoromethylation of (hetero)arenes with stable and inexpensive CF3SO2Na as the trifluoromethyl (TFM) source via radical pathway. Either CdS or g-C3N4 propagated reaction can efficiently transform CF3SO2Na to [rad]CF3 radical and further afford the desired benzotrifluoride derivatives in moderate to good yields. After visible light initiated photocatalytic process, the key elements (such as F, S and C) derived from the starting TFM source of CF3SO2Na exhibited differential chemical forms as compared to those in other oxidative reactions. The photogenerated electron was trapped by chemisorbed O2 on photocatalysts to form superoxide radical anion (O2[rad]−) which will further attack [rad]CF3 radical with the generation of inorganic product F− and CO2. This resulted in a low utilization efficiency of [rad]CF3 (&lt;50%). When nitro aromatic compounds and CF3SO2Na served as the starting materials in inert atmosphere, the photoexcited electrons can be directed to reduce the nitro group to amino group rather than being trapped by O2. Meanwhile, the photogenerated holes oxidize SO2CF3− into [rad]CF3. Both the photogenerated electrons and holes were engaged in reductive and oxidative paths, respectively. The desired product, trifluoromethylated aniline, was obtained successfully via one-pot free-radical synthesis.</p

Facile One-Pot Solvothermal Method to Synthesize Sheet-on-Sheet Reduced Graphene Oxide (RGO)/ZnIn₂S₄ Nanocomposites with Superior Photocatalytic Performance

Highly reductive RGO (reduced graphene oxide)/ZnIn₂S₄ nanocomposites with a sheet-on-sheet morphology have been prepared via a facile one-pot solvothermal method in a mixture of <i>N</i>,<i>N</i>-dimethylformamide (DMF) and ethylene glycol (EG) as solvent. A reduction of GO (graphene oxide) to RGO and the formation of ZnIn₂S₄ nanosheets on highly reductive RGO has been simultaneously achieved. The effect of the solvents on the morphology of final products has been investigated and the formation mechanism was proposed. The as-prepared RGO/ZnIn₂S₄ nanoscomposites were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), N₂-adsorption BET surface area, UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM). The photocatalytic activity for hydrogen evolution under visible light irradiations over the as-prepared RGO/ZnIn₂S₄ nanocomposites has been investigated. The as-prepared RGO/ZnIn₂S₄ nanocomposites show enhanced photocatalytic activity for hydrogen evolution under visible light irradiations and an optimum photocatalytic activity is observed over 1.0 wt % RGO incorporated ZnIn₂S₄ nanocomposite. The superior photocatalytic performance observed over RGO/ZnIn₂S₄ nanocomposites can be ascribed to the existence of highly reductive RGO which has strong interactions with ZnIn₂S₄ nanosheets. The existence of the strong interaction between ZnIn₂S₄ nanosheets and RGO in the nancomposites facilitates the electron transfer from ZnIn₂S₄ to RGO, with the latter serving as a good electron acceptor, mediator as well as the co-catalyst for hydrogen evolution. This study can provide some guidance for us in the developing of RGO-incorporated nanocomposite photocatalysts

Visible Light Photoredox Catalyzed Biaryl Synthesis Using Nitrogen Heterocycles as Promoter

Although transition-metal-catalyzed direct arylation of aromatic C–H bonds is one of the most efficient ways for the construction of biaryl targets, it is also expected for other alternative methods that can use inexpensive catalysts and abundant solar energy to drive chemical reactions. Herein, we describe a new activation mode for biaryl synthesis by using a photosensitive complex of potassium <i>tert</i>-butoxide (KO<i>t</i>-Bu) and nitrogenous heterocyclic ligands via visible light excitation. Under low-energy visible light irradiation, the single-electron transfer from electron-donor KO<i>t</i>-Bu to electron-deficient nitrogenous heterocycle occurred in the inner part of the complex by using potassium as a bridge atom. The ligand accepted the as-photoexcited single electron and transformed into stable radical anions which played a dominant role in the coupling reactions of benzene with aryl halides at ambient temperature. This reaction paradigm features the use of inexpensive catalyst, abundant visible light energy, and more accessible bromobenzene for the construction of biaryl compounds under rather mild conditions

Quinone-Mediated Trifluoromethylation of Arenes and Heteroarenes with Visible Light

The trifluoromethyl group can significantly influence the physical and chemical properties of organic molecules, thereby increasing their applications in the fields of pharmaceuticals, agrochemicals, and organic materials. An efficient visible-light-promoted method for the direct trifluoromethylation of arenes and heteroarenes has been developed using inexpensive CF₃SO₂Na as the CF₃ radical source and naturally ubiquitous quinones as oxidants. The regeneration of quinones was successfully realized by using a MnO₂-fixed bed. This operationally simple methodology not only provides an access to a wide variety of CF₃-containing building blocks from simple starting materials but also exhibits potential applications on a larger scale synthesis utilizing visible light energy

Isolation and characteristic analysis of a novel strain H7N9 of avian influenza virus A from a patient with influenza-like symptoms in China

A novel H7N9 virus (A/Changsha/1/2013(H7N9)) identified through routine examination in the influenza network laboratory was analyzed retrospectively. The gene sequences of A/Changsha/1/2013(H7N9) were highly homologous to other viruses isolated in mainland China. Mutations of Q226L and G186 V were found in the hemagglutinin protein (HA). Amino acid deletions were found at positions 69–73 of the neuraminidase protein (NA) and 218–230 of the non-structural protein (NS1). All viral genes except PB1 were essentially identical to the sequences of other Chinese influenza A H7N9 isolates. Overall, A/Changsha/1/2013(H7N9) is highly homologous to other H7N9 avian influenza viruses isolated in mainland China

A Templated Method to Bi₂WO₆ Hollow Microspheres and Their Conversion to Double-Shell Bi₂O₃/Bi₂WO₆ Hollow Microspheres with Improved Photocatalytic Performance

Bi₂WO₆ hollow microspheres with dimension of ca. 1.5 μm were synthesized via a hydrothermal method using polystyrene particles as the template. The as-prepared Bi₂WO₆ hollow microspheres can be further transformed to double-shell Bi₂O₃/Bi₂WO₆ hollow microspheres. The samples were fully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, N₂-sorption Brunauer–Emmett–Teller surface area, UV–vis diffuse-reflectance spectroscopy, and X-ray photoelectron spectroscopy. The as-formed double-shell Bi₂O₃/Bi₂WO₆ hollow microspheres exhibit enhanced photocatalytic activity due to the hollow nature and formation of the p–n junction between p-type Bi₂O₃ and n-type Bi₂WO₆. The study provides a general and effective method in the fabrication of composition and dimension-tunable composite hollow microspheres with sound heterojunctions that may show a variety of applications