Synergy of redox-activity and hemilability in thioamidato cobalt(III) complexes for the chemoselective reduction of nitroarenes to anilines: catalytic and mechanistic investigation.

Reduction of nitro-compounds to amines is one of the most often employed and challenging catalytic processes in the fine and bulk chemical industry. Herein, we present two series of mononuclear homoleptic and heteroleptic Co(III) complexes, , [Co(LS)] and [Co(LS)LL], respectively ( = 0 or 1, LS = pyrimidine- or pyridine-thioamidato, L/L = thioamidato, phosphine or pyridine), which successfully catalyze the transformation of nitroarenes to anilines by methylhydrazine. The catalytic reaction can be accomplished for a range of electronically and sterically diverse nitroarenes, using mild experimental conditions and low catalyst loadings, resulting in the corresponding anilines in high yields, with high chemoselectivity, and no side-products.

One-Pot Synthetic Approach to 3-Carboxyl- and 3-Ketopyridines in Aqueous Media.

We describe a one-pot strategy to access 3-carboxyl- and 3-ketopyridines from readily available alkynes and propargylamine a hydroamination process. This one-pot protocol uses alkynes as starting materials, has a broad substrate scope, and operates in aqueous media and open-air conditions. A series of aryl- and alkyl-substituted pyridines were synthesized.

Simple Synthetic Approach to -(Pyridin-2-yl)imidates from Nitrostyrenes and 2-Aminopyridines via the -(Pyridin-2-yl)iminonitriles as Intermediates.

A facile, green, synthetic protocol of several substituted -(pyridin-2-yl)imidates from nitrostyrenes and 2-aminopyridines via the corresponding -(pyridin-2-yl)iminonitriles as intermediates is reported. The reaction process involved the in situ formation of the corresponding α-iminontriles under heterogeneous Lewis acid catalysis in the presence of AlO. Subsequently, α-iminonitriles were selectively transformed into the desired -(pyridin-2-yl)imidates under ambient conditions and in the presence of CsCO in alcoholic media.

Biological Response of Human Cancer Cells to Ionizing Radiation in Combination with Gold Nanoparticles.

In the context of improving radiation therapy, high-atomic number (Z) metallic nanoparticles and, more importantly, gold-based nanostructures are developed as radiation enhancers/radiosensitizers. Due to the diversity of cell lines, nanoparticles, as well as radiation types or doses, the resulting biological effects may differ and remain obscure. In this multiparameter study, we aim to shed light on these effects and investigate them further by employing X-irradiation and three human cancer cell lines (PC3, A549, and U2OS cells) treated by multiple techniques.

Supported Gold Nanoparticle-Catalyzed Selective Reduction of Multifunctional, Aromatic Nitro Precursors into Amines and Synthesis of 3,4-Dihydroquinoxalin-2-Ones.

The synthesis of 3,4-dihydroquinoxalin-2-ones via the selective reduction of aromatic, multifunctional nitro precursors catalyzed by supported gold nanoparticles is reported. The reaction proceeds through the in situ formation of the corresponding amines under heterogeneous transfer hydrogenation of the initial nitro compounds catalyzed by the commercially available Au/TiO-EtSiH catalytic system, followed by an intramolecular C-N transamidation upon treatment with silica acting as a mild acid. Under the present conditions, the Au/TiO-TMDS system was also found to catalyze efficiently the present selective reduction process.

Polyoxometalate-Driven Ease Conversion of Valuable Furfural to -,-4,5-Diaminocyclopenten-2-ones.

We investigated the catalytic efficacy of silicotungstic acid (HSiWO) polyoxometalate (POM) toward the reaction between furfural and amines that selectively yields -,-4,5-substituted-diaminocyclopenten-2-ones (-DACPs). HSiWO facilitates the synthesis of a library of -DACPs with loadings as low as 0.05 mol %, in open air, without additives, in short times and good to high isolated yields.

Direct and Indirect Chemiluminescence: Reactions, Mechanisms and Challenges.

Emission of light by matter can occur through a variety of mechanisms. When it results from an electronically excited state of a species produced by a chemical reaction, it is called chemiluminescence (CL). The phenomenon can take place both in natural and artificial chemical systems and it has been utilized in a variety of applications.

Selective Mild Oxidation of Anilines into Nitroarenes by Catalytic Activation of Mesoporous Frameworks Linked with Gold-Loaded Mn O Nanoparticles.

This work reports the synthesis and catalytic application of mesoporous Au-loaded Mn O nanoparticle assemblies (MNAs) with different Au contents, i. e., 0.

Selective C-H Allylic Oxygenation of Cycloalkenes and Terpenoids Photosensitized by [Cu(Xantphos)(neoc)]BF.

We present herein for the first time the use of the [Cu(Xantphos)(neoc)]BF as a photocatalyst for the selective C-H allylic oxygenation of cycloalkenes into the corresponding allylic hydroperoxides or alcohols in the presence of molecular oxygen. The proposed methodology affords the products at good yields and has also been applied successfully to several bioactive terpenoids, such as geraniol, linalool, β-citronellol, and phytol. A mechanistic study involving also kinetic isotope effects (KIEs) supports the proposed singlet oxygen-mediated reaction.

Skeletally Tunable Seven-Membered-Ring Fused Pyrroles.

We describe a copper-mediated method that enables the synthesis of seven-membered-ring fused pyrroles (7-mrFPs). The protocol proceeds via an in situ spiro-intermediate ring expansion and tolerates a library of 7-mrFP derivatives with a broad range of functional groups in a simple step with tangible parameters and substrate adaptations. These rare 7-mrFPs are now accessible on a millimolar scale, and selected examples exhibit high antioxidant activity.

Selective Reduction of Nitroarenes to Arylamines by the Cooperative Action of Methylhydrazine and a Tris(-heterocyclic thioamidate) Cobalt(III) Complex.

We report an efficient catalytic protocol that chemoselectively reduces nitroarenes to arylamines, by using methylhydrazine as a reducing agent in combination with the easily synthesized and robust catalyst tris(-heterocyclic thioamidate) Co(III) complex [Co(κ,-tfmp2S)], tfmp2S = 4-(trifluoromethyl)-pyrimidine-2-thiolate. A series of arylamines and heterocyclic amines were formed in excellent yields and chemoselectivity. High conversion yields of nitroarenes into the corresponding amines were observed by using polar protic solvents, such as MeOH and PrOH.

Selective Synthesis of Benzimidazoles from -Phenylenediamine and Aldehydes Promoted by Supported Gold Nanoparticles.

We investigated the catalytic efficacy of supported gold nanoparticles (AuNPs) towards the selective reaction between -phenylenediamine and aldehydes that yields 2-substituted benzimidazoles. Among several supported gold nanoparticle platforms, the Au/TiO provides a series of 2-aryl and 2-alkyl substituted benzimidazoles at ambient conditions, in the absence of additives and in high yields, using the mixture CHCl:MeOH in ratio 3:1 as the reaction solvent. Among the AuNPs catalysts used herein, the Au/TiO containing small-size nanoparticles is found to be the most active towards the present catalytic methodology.

Selective Photoinduced Reduction of Nitroarenes to -Arylhydroxylamines.

We report the selective photoinduced reduction of nitroarenes to -arylhydroxylamines. The present methodology facilitates this transformation in the absence of catalyst or additives and uses only light and methylhydrazine. This noncatalytic photoinduced transformation proceeds with a broad scope, excellent functional-group tolerance, and high yields.

Alumina-Supported Gold Nanoparticles as a Bifunctional Catalyst for the Synthesis of 2-Amino-3-arylimidazo[1,2-]pyridines.

The bifunctional catalytic efficacy of alumina-supported gold nanoparticles (Au/AlO) was investigated for the synthesis of a series of 2-amino-3-aryl-imidazopyridines through the chemoselective reduction of the corresponding 2-nitro-3-aryl-imidazo[1,2-]pyridines in high isolated yields. This highly efficient protocol was initially applied for the synthesis of 2-nitro-3-aryl imidazo[1,2-]pyridines via the reaction between 2-aminopyridine and nitroalkenes catalyzed by the present catalytic system Au/AlO. Moreover, the heterogeneous surface γ-AlO was also found to catalyze this pathway in a comparable manner.

Application of Silver Nanoparticles in the Multicomponent Reaction Domain: A Combined Catalytic Reduction Methodology to Efficiently Access Potential Hypertension or Inflammation Inhibitors.

The catalytic efficacy of silver nanoparticles was investigated toward the chemoselective reduction of nitro-tetrazole or amino acid-substituted derivatives into the corresponding amines in high isolated yields. This highly efficient protocol was thereafter applied toward the multicomponent reaction synthesis of heterocyclic dihydroquinoxalin-2-ones with high isolated yields. The reaction proceeds with low catalyst loading (0.

Copper(ii)-benzotriazole coordination compounds in click chemistry: a diagnostic reactivity study.

This diagnostic study aims to shed light on the catalytic activity of a library of Cu(ii) based coordination compounds with benzotriazole-based ligands. We report herein the synthesis and characterization of five new coordination compounds formulated as [Cu(L)(MeCN)(CFSO)] (1), [Cu(L)(CFSO)] (2), [Cu(L)(MeCN)(CFSO)]·(CFSO) (3), [Cu(L)(HO)(CFSO)]·(CFSO)·2(MeCO) (4), and [Cu(L)(L)(CFSO)]·4(CFSO)·8(MeCO) (5), derived from similar nitrogen-based ligands. The homogeneous catalytic activity of these compounds along with our previously reported coordination compounds (6-13), derived from similar ligands, is tested against the well-known Cu(i)-catalysed azide-alkyne cycloaddition reaction.

Copper-Promoted Regioselective Synthesis of Polysubstituted Pyrroles from Aldehydes, Amines, and Nitroalkenes via 1,2-Phenyl/Alkyl Migration.

The facile copper-catalyzed synthesis of polysubstituted pyrroles from aldehydes, amines, and β-nitroalkenes is reported. Remarkably, the use of α-methyl-substituted aldehydes provides efficient access to a series of tetra- and pentasubstituted pyrroles via an overwhelming 1,2-phenyl/alkyl migration. The present methodology is also accessible to non α-substituted aldehydes, yielding the corresponding trisubstituted pyrroles.

Mechanistic Studies on the Michael Addition of Amines and Hydrazines To Nitrostyrenes: Nitroalkane Elimination via a Retro-aza-Henry-Type Process.

In this article we report on the mechanistic studies of the Michael addition of amines and hydrazines to nitrostyrenes. Under the present conditions, the corresponding N-alkyl/aryl substituted benzyl imines and N-methyl/phenyl substituted benzyl hydrazones were observed via a retro-aza-Henry-type process. By combining organic synthesis and characterization experiments with computational chemistry calculations, we reveal that this reaction proceeds via a protic solvent-mediated mechanism.

Cu(II) Coordination Polymers as Vehicles in the A Coupling.

A family of benzotriazole based coordination compounds, obtained in two steps and good yields from commercially available materials, formulated as [Cu(L)(MeCN)]·2ClO·MeCN (1), [Cu(L)(NO)]·MeCN (2), [Zn(L)(HO)]·2ClO·2MeCN (3), [Cu(L)Cl] (4), [Cu(L)Cl] (5), [Cu(L)Br]·4MeCN·CuBr (6), [Cu(L)(MeCN)]·2BF (7), [Cu(L)(CFSO)] (8), [Zn(L)(MeCN)]·2CFSO (9), [Cu(L)(HO)]·4CFSO·4MeCO (10), and [Cu(L)(CFSO)]·2CFSO·MeCO (11), are reported. These air-stable compounds were tested as homogeneous catalysts for the A coupling synthesis of propargylamine derivatives from aldehyde, amine, and alkyne under a noninert atmosphere. Fine tuning of the catalyst resulted in a one-dimensional (1D) coordination polymer (CP) (8) with excellent catalytic activity in a wide range of substrates, avoiding any issues that would inhibit its performance.

Reduction of Nitroarenes into Aryl Amines and N-Aryl hydroxylamines via Activation of NaBH₄ and Ammonia-Borane Complexes by Ag/TiO₂ Catalyst.

In this study, we report the fabrication of mesoporous assemblies of silver and TiO₂ nanoparticles (Ag/MTA) and demonstrate their catalytic efficiency for the selective reduction of nitroarenes. The Ag/TiO₂ assemblies, which show large surface areas (119-128 m²·g) and narrow-sized mesopores ( 7.1-7.

Gold nanoparticles, radiations and the immune system: Current insights into the physical mechanisms and the biological interactions of this new alliance towards cancer therapy.

Considering both cancer's serious impact on public health and the side effects of cancer treatments, strategies towards targeted cancer therapy have lately gained considerable interest. Employment of gold nanoparticles (GNPs), in combination with ionizing and non-ionizing radiations, has been shown to improve the effect of radiation treatment significantly. GNPs, as high-Z particles, possess the ability to absorb ionizing radiation and enhance the deposited dose within the targeted tumors.

Mesoporous Assembled Mn O Nanoparticle Networks as Efficient Catalysts for Selective Oxidation of Alkenes and Aryl Alkanes.

The design of nanoscale materials has been considered important for enhancing their surface properties for catalysis. Metal oxide nanoparticles have a large number of exposed surface active sites, but they suffer from low reactivity and poor stability resulting from excessive aggregation into less active microscopic structures. Herein, the synthesis of mesoporous Mn O nanoparticle assemblies by polymer-assisted self-assembly is presented and their catalytic activity is demonstrated in the oxidation of various saturated and unsaturated hydrocarbons, including aromatic alkenes and aryl alkanes, in the presence of tert-butyl hydroperoxide as a mild oxidant.

Controllable Synthesis of Mesoporous Iron Oxide Nanoparticle Assemblies for Chemoselective Catalytic Reduction of Nitroarenes.

Iron(III) oxide is a low-cost material with applications ranging from electronics to magnetism, and catalysis. Recent efforts have targeted new nanostructured forms of Fe2O3 with high surface area-to-volume ratio and large pore volume. Herein, the synthesis of 3D mesoporous networks consisting of 4-5 nm γ-Fe2O3 nanoparticles by a polymer-assisted aggregating self-assembly method is reported.

Green photocatalytic organic transformations by polyoxometalates vs. mesoporous TiO2 nanoparticles: selective aerobic oxidation of alcohols.

In this study, the catalytic activity of decatungstate (W10O32(4-)) supported on mesoporous TiO2 nanoparticle assemblies (DT-MTA) was compared with that of homogeneous [Bu4N]4W10O32 catalysts under mild conditions. Our experiments showed that both catalytic systems achieve exceptionally high activity and selectivity under UV-visible light oxidation of various para-substituted aryl alcohols, using molecular oxygen as a "green" oxidant. The chemoselective transformation of aryl alcohols into the corresponding ketones was investigated with gas chromatography (GC) and NMR spectroscopy.

Cyclization of 1,6-enynes catalyzed by gold nanoparticles supported on TiO2: significant changes in selectivity and mechanism, as compared to homogeneous Au-catalysis.

Gold nanoparticles supported on TiO(2) (1.2 mol %) catalyze, for the first time under heterogeneous conditions, the cycloisomerization of a series of 1,6-enynes in high yields. In several cases, the product selectivity differs significantly as compared to homogeneous Au(I)-catalysis.