Selective ruthenium-catalyzed methylation of 2-arylethanols using methanol as C1 feedstock

We describe the selective cross coupling of methanol and 2-arylethanols using a combination of Ru-MACHO (RuHCl(PNP(Ph))CO) and Shvo's diruthenium complex as catalysts. The desired domino transformation takes place via so-called borrowing hydrogen methodology, which constitutes an ideal example of green chemistry.

Hydrogenation using iron oxide-based nanocatalysts for the synthesis of amines

In this protocol, we describe the preparation of nanoscale iron oxide-based materials and their use in the catalysis of different hydrogenation reactions. Pyrolysis of a Fe(OAc)2-phenanthroline complex on carbon at 800 °C under argon atmosphere results in the formation of nanoscale Fe2O3 particles surrounded by nitrogen-doped graphene layers. By applying these catalysts, the hydrogenation of structurally diverse and functionalized nitroarenes to anilines proceeds with excellent selectivity. Furthermore, we have shown that one-pot reductive amination of carbonyl compounds with nitroarenes is also possible in the presence of these iron oxide catalysts. We report herein the synthesis of more than 40 amines, which are important feedstocks and key intermediates for pharmaceuticals, agrochemicals and polymers. The detailed preparation of the catalysts and the procedures for the hydrogenation processes are presented. The overall time required for the catalyst preparation and for the hydrogenation reactions are 35 h and 20-35 h, respectively.

Iridium-catalyzed hydrogen production from monosaccharides, disaccharide, cellulose, and lignocellulose

Hydrogen constitutes an important feedstock for clean-energy technologies as well as for production of bulk and fine chemicals. Hence, the development of novel processes to convert easily available biomass into H2 is of general interest. Herein, we demonstrate a one-pot protocol hydrogen generation from monosaccharides, disaccharide, and extremely demanding cellulose and lignocellulose substrates by using a pincer-type iridium catalyst. Applying ppm amounts of this catalyst, hydrogen is produced at temperatures lower than 120 °C. More specifically, catalyst turnover numbers (TONs) for lignocellulose from bamboo reached up to about 3000. Interestingly, even (used) cigarette filters, which are composed of cellulose acetate, produce hydrogen under optimized conditions.

"Nanorust"-catalyzed benign oxidation of amines for selective synthesis of nitriles

Organic nitriles constitute key precursors and central intermediates in organic synthesis. In addition, nitriles represent a versatile motif found in numerous medicinally and biologically important compounds. Generally, these nitriles are synthesized by traditional cyanation procedures using toxic cyanides. Herein, we report the selective and environmentally benign oxidative conversion of primary amines for the synthesis of structurally diverse aromatic, aliphatic and heterocyclic nitriles using a reusable "nanorust" (nanoscale Fe2 O3 )-based catalysts applying molecular oxygen.

Spin density distribution after electron transfer from triethylamine to an [Ir(ppy)2(bpy)]+ photosensitizer during photocatalytic water reduction

The photoreduction of the bis(2-phenylpyridinato-)(2,2'-bipyridine)iridium(III) ion ([Ir(ppy)2(bpy)](+)), used as a photosensitizer in photocatalytic water splitting, by triethylamine was studied by means of UV/VIS, XANES, and EPR spectroscopies, supported by theoretical calculations at density functional theory (DFT) and complete active space self-consistent field (CASSCF/CASPT2) levels. The combination of these methods suggests a predominant bpy localization of the spin-density of the unpaired electron with notable delocalization to the Ir center. This is particularly evident from EPR and theoretical results and leads to broad EPR lines and a large anisotropy of the g-factor.

Substitution-controlled excited state processes in heteroleptic copper(I) photosensitizers used in hydrogen evolving systems

Four different heteroleptic [Cu(N^N)(P^P)]PF6 complexes, which combine classical bidentate diimine ligands and sterically demanding diphosphine ligands, are studied by a combination of ultrafast time-resolved spectroscopy and quantum chemical calculations. The light-induced excited state processes, accompanied by a structural change, are discussed with respect to the application of these complexes as a new class of noble-metal-free photosensitizers in proton reducing systems. In particular, the influence of different substituents in the ligand backbone on the photophysical properties is highlighted.

Efficient and selective hydrogen generation from bioethanol using ruthenium pincer-type complexes

Catalytic generation of hydrogen from aqueous ethanol solution proceeds in the presence of pincer-type transition metal catalysts. Optimal results are obtained applying a [Ru(H)(Cl)(CO)(iPr2PEtN(H)EtPiPr2)] complex (catalyst TON 80,000) in the presence of water and base. This dehydrogenation reaction provides up to 70% acetic acid in a selective manner. For the first time, it is shown that bioethanol obtained from fermentation processes can be used directly in this protocol without the need for water removal. The produced hydrogen can be directly utilized in proton exchange membrane (PEM) fuel cells, since very low amounts of CO are formed.

Green synthesis of nitriles using non-noble metal oxides-based nanocatalysts

(Hetero)aromatic and aliphatic nitriles constitute major building blocks for organic synthesis and represent a versatile motif found in numerous medicinally and biologically important compounds. In general, these nitriles are synthesized by traditional cyanation procedures using toxic cyanides. With respect to green chemistry, the development of more sustainable and cost-efficient processes for the synthesis of advanced nitriles is highly desired. Here we report an environmentally benign synthesis of all kinds of structurally diverse aryl, heterocyclic, allylic and aliphatic nitriles from easily available alcohols applying aqueous ammonia and molecular oxygen. Key to success for this synthesis is the use of nitrogen-doped graphene-layered non-noble metal oxides as stable and durable nanocatalysts. As an example a renewable synthesis of adiponitrile, an industrially important bulk chemical is presented.

Electron- and Energy-Transfer Processes in a Photocatalytic System Based on an Ir(III)-Photosensitizer and an Iron Catalyst

The reaction pathways of bis-(2-phenylpyridinato-)(2,2'-bipyridine)iridium(III)hexafluorophosphate [Ir(ppy)2(bpy)]PF6 within a photocatalytic water reduction system for hydrogen generation based on an iron-catalyst were investigated by employing time-resolved photoluminescence spectroscopy and time-dependent density functional theory. Electron transfer (ET) from the sacrificial reagent to the photoexcited Ir complex has a surprisingly low probability of 0.4% per collision. Hence, this step limits the efficiency of the overall system. The calculations show that ET takes place only for specific encounter geometries. At the same time, the presence of the iron-catalyst represents an energy loss channel due to a triplet-triplet energy transfer of Dexter type. This loss channel is kept small by the employed concentration ratios, thus favoring the reductive ET necessary for the water reduction. The elucidated reaction mechanisms underline the further need to improve the sun light's energy pathway to the catalyst to increase the efficiency of the photocatalytic system.

Acinar cell carcinoma of exocrine pancreas in two horses

Two horses were presented with non-specific clinical signs of several weeks' duration and were humanely destroyed due to a poor prognosis. At necropsy examination, both horses had multiple small, white nodules replacing pancreatic tissue and involving the serosal surface of the abdominal cavity, the liver and the lung. Microscopically, neoplastic cells were organized in acini and contained abundant (case 1) or sparse (horse 2) intracytoplasmic zymogen granules. Immunohistochemically, both tumours expressed amylase and pan-cytokeratin, but not insulin or neuron-specific enolase. In case 2, a low percentage of neoplastic cells expressed glucagon and synaptophysin. The presence of zymogen granules was confirmed in both cases by electron microscopy and occasional fibrillary or glucagon granules were observed in cases 1 and 2, respectively. A diagnosis of pancreatic acinar cell carcinoma was established in both horses.

Nanoscale Fe2O3-based catalysts for selective hydrogenation of nitroarenes to anilines

Production of anilines--key intermediates for the fine chemical, agrochemical, and pharmaceutical industries--relies on precious metal catalysts that selectively hydrogenate aryl nitro groups in the presence of other easily reducible functionalities. Herein, we report convenient and stable iron oxide (Fe2O3)-based catalysts as a more earth-abundant alternative for this transformation. Pyrolysis of iron-phenanthroline complexes on carbon furnishes a unique structure in which the active Fe2O3 particles are surrounded by a nitrogen-doped carbon layer. Highly selective hydrogenation of numerous structurally diverse nitroarenes (more than 80 examples) proceeded in good to excellent yield under industrially viable conditions.