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.

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.

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 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.

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 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.

Synthesis and Biological Evaluation of Novel Hybrid Molecules Containing Purine, Coumarin and Isoxazoline or Isoxazole Moieties.

Introduction: The 1,3-dipolar cycloaddition reactions of nitrile oxides formed (in the presence of NCS and EtN) from the oximes of (purin-9-yl)acetaldehyde or (coumarinyloxy)acetaldehyde with allyloxycoumarins or 9-allylpurines, respectively resulted in 3,5-disubstituted isoxazolines. The similar reactions of propargyloxycoumarins or 9-propargylpurines led to 3,5-disubstituted isoxazoles by treatment with PIDA and catalytic amount of TFA.

Methods: The new compounds were tested as antioxidant agents and inhibitors of soybean lipoxygenase LO, AChE and MAO-B.

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.

Purine homo-N-nucleoside+coumarin hybrids as pleiotropic agents for the potential treatment of Alzheimer's disease.

Aim: Due to the complex nature of Alzheimer's disease, there is a renewed search for pleiotropic agents.

Results: Purine+coumarin hybrids have been synthesized and tested for the potential treatment of Alzheimer's disease. Hybrids 6, 4a-b, 14c and 14e inhibit significantly soybean lipoxygenase, whereas derivatives 14b, c and 20a present antioxidative/lipoxygenase inhibition activities.

Synthesis of purine homo-N-nucleosides modified with coumarins as free radicals scavengers.

Cross metathesis (CM) of 9-butenylpurines with 4-butenyloxycoumarin in the presence of Grubbs 2nd generation catalyst under MW irradiation resulted to conjugated compounds containing homo-N-nucleosides and coumarins. Analogous derivatives received by the CM reaction of 9-butenyl-6-piperidinylpurine with 6- or 7-butenyloxycoumarins, allyloxycoumarins or coumarinyl acrylate. These compounds were tested in vitro for their antioxidant activity and they present significant scavenging activity.

Synthesis of hydroxycoumarins and hydroxybenzo[f]- or [h]coumarins as lipid peroxidation inhibitors.

Substituted hydroxycoumarins and 7- or 8-hydroxybenzo[f]coumarins were prepared by the treatment of phenols and naphthalenediols, respectively, with malic acid and H(2)SO(4) under microwave irradiation. 7- or 8-Hydroxybenzo[f]coumarins and 6-hydroxybenzo[h]coumarin were synthesized by the reaction of naphthalenediols with ethylpropiolate in the presence of ZnCl(2) in refluxing dioxane. The compounds were tested in vitro for their ability: (i) to interact with 1,1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical, (ii) to inhibit lipid peroxidation, (iii) to scavenge the superoxide anion, (iv) to inhibit the activity of soybean lipoxygenase and (v) to inhibit in vivo the carrageenin-induced rat paw edema.