Novel ultra-small Pd NPs on SOS spheres: a new catalyst for domino intramolecular Heck and intermolecular Sonogashira couplings.

We report a novel catalyst Pd/SOS that catalyzes the dual C-C bond forming coupling of an iodoarene moiety with an internal alkene and an external alkyne via an intramolecular Heck reaction, followed by an intermolecular Sonogashira reaction, respectively. The catalyst was characterized using XRD, IR, XPS, SEM and TEM analyses. Notably, for the first time, cheap and readily available new silica [nanosilica on microsilica (SOS)] material-supported ultra-small Pd nanoparticles (2.20 nm) are employed for the efficient synthesis of dihydrobenzofuran and oxindole derivatives in a domino one-pot reaction. Significantly, a sub-molar quantity of Pd (0.3 mol%) was found to be sufficient to furnish the products in very good to near quantitative yields. Gratifyingly, the catalyst could be recycled up to five cycles with a marginal loss (∼no loss) of the product.

Reduced graphene oxide supported ZnO quantum dots for visible light-induced simultaneous removal of tetracycline and hexavalent chromium.

Semiconducting nanomaterials play an important role in the photocatalytic removal of aqueous pollutants like heavy metals, organic compounds, pathogens and antibiotics. In this study, we prepared ZnO quantum dots (QD) by the precipitation method and ZnO/rGO materials with varying percentages (0.5-2 wt%) of ZnO were prepared by the hydrothermal method. The synthesized catalysts were characterized by various physicochemical techniques, such as powder X-ray diffraction (XRD), Raman spectroscopy, ultraviolet-visible-diffuse reflectance spectroscopy (UV-VIS-DRS), Transmission Electron Microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) analysis to determine the structural as well as textural and surface properties. The photocatalytic activity of the prepared catalysts was analyzed during the individual and simultaneous removal of tetracycline (TC) and hexavalent chromium [Cr(vi)] in aqueous medium. Among all the catalysts, 1.5 wt% ZnO/rGO showed the highest visible light activity, where 68% tetracycline and 84% Cr(vi) abatement was observed after 120 min irradiation time. Moreover, tetracycline showed 70% mineralization. The photocatalytic activity is explained based on the photo-generated electron transfer from the conduction band (CB) of ZnO to the surface of rGO which prevents the recombination of excitons and produces OH˙ and O2 -˙; these radicals play an important role in degrading the TC and Cr(vi). The mechanism suggested that the co-existence of oxidizable and reducible species such as TC and Cr(vi) ensured the effective use of the photo-generated electrons and holes that leads to the efficient oxidation of TC and Cr(vi) reduction.

Bimetallic Pd-Au/TiO2 Nanoparticles: An Efficient and Sustainable Heterogeneous Catalyst for Rapid Catalytic Hydrogen Transfer Reduction of Nitroarenes.

Anilines are one of the important chemical feedstocks and are utilized for the preparation of a variety of pharmaceuticals, agrochemicals, pigments, and dyes. In this context, the catalytic reduction of nitro functionality is an industrially vital process for the synthesis of aniline derivatives. Herein, we report an efficient nanosized bimetallic Pd-Au/TiO2 nanomaterial which is proved to be quite efficient for rapid catalytic hydrogen transfer reduction of nitroarenes into corresponding amines. Significantly, the reduction process is successful under solvent-free and mild green atmospheric conditions. Bimetallic Pd-Au nanoparticles served as the active center, and TiO2 played as a support in hydrogen transfer from the source hydrazine monohydrate. Typical results highlighted that the reactions were very rapid and the products were obtained in good to excellent yields. Significantly, the process was successful in the presence of a very low amount catalyst (0.1 mol %). Furthermore, the reaction showed good chemoselectivity and compatiblity with double or triple bond, aldehyde, ketone, and ester functionalities on the aromatic ring. Typical results indicated the true heterogeneous nature of the Pd-Au/TiO2 nanocatalyst, where the catalyst retained the activity, without loss of its activity.

Recyclable Pd/CuFe2O4 nanowires: a highly active catalyst for C-C couplings and synthesis of benzofuran derivatives.

Pd/CuFe2O4 nanowire-catalyzed cross coupling transformations are described. Notably, these reactions showed excellent functional group tolerance. Further, the protocol is applied to a one-pot synthesis of benzofurans via a Sonogashira coupling and intramolecular etherification sequence. The catalyst was reused and found to maintain its activity and stability.