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A new series of half-sandwich (η6-p-cymene) ruthenium(II) complexes with thiophene-2-carboxylic acid hydrazide derivatives [Ru(η6-p-cymene)(Cl)(L)] [L = N'-(naphthalen-1-ylmethylene)thiophene-2-carbohydrazide (L1), N'-(anthracen-9-ylmethylene)thiophene-2-carbohydrazide (L2) and N'-(pyren-1-ylmethylene)thiophene-2-carbohydrazide (L3)] were synthesized. The ligand precursors and their Ru(II) complexes (1–3) were structurally characterized by spectral (IR, UV–Vis, NMR and mass spectrometry) and elemental analysis. The molecular structures of the ruthenium(II) complexes 1–3 were determined by single-crystal X-ray diffraction. All complexes were used as catalysts for the one-pot three-component syntheses of 2,4,5-trisubstitued imidazole and 5-substituted 1H-tetrazole derivatives. The catalytic studies optimized parameters as solvent, temperature and catalyst. The catalysts revealed very active for a broad range of aromatic aldehydes presenting either electron attractor or electron donor substituents and, although less active, moderate to high activities were observed for alkyl aldehydes.

A new, efficient and convenient method for the synthesis of 5-substituted 1H-tetrazole derivatives with a wide range of substituents in good to excellent yields has been developed. The synthesis was performed by the one-pot three-component [3+2]cycloaddit

Histone deacetylase 6 (HDAC6) is a peculiar HDAC isoform whose expression and functional alterations have been correlated with a variety of pathologies such as autoimmune disorders, neurodegenerative diseases, and cancer. It is primarily a cytoplasmic protein, and its deacetylase activity is focused mainly on nonhistone substrates such as tubulin, heat shock protein (HSP)90, Foxp3, and cortactin, to name a few. Selective inhibition of HDAC6 does not show cytotoxic effects in healthy cells, normally associated with the inhibition of Class I HDAC isoforms. Here, we describe the design and synthesis of a new class of potent and selective HDAC6 inhibitors that bear a pentaheterocyclic central core. These compounds show a remarkably low toxicity both in vitro and in vivo and are able to increase the function of regulatory T cells (Tregs) at well-tolerated concentrations, suggesting a potential clinical use for the treatment of degenerative, autoimmune diseases and for organ transplantation.

Benzoylhydrazine based Schiff base-ligated two new copper(II) complexes, [Cu(L1)2] (1) and [Cu(L2)2] (2) were synthesized by the reaction of Cu(CH3COO)2·H2O with respective Schiff base ligand 1-[(4-nitrophenyl)ethylidene] benzohydrazide (HL1) or 1-[(4-methoxyphenyl)ethylidene] benzohydrazide (HL2). Both complexes were isolated as greenish solid and fully characterized by elemental analysis, FT-IR, EPR, thermo-gravimetric (TG) analysis and Cyclic Voltammetry. The molecular structures of both complexes have also been determined by single crystal X-ray crystallography, which confirmed the coordination of Schiff base ligands through N, O donor atoms and distorted square planar geometry around the Cu(II) ion. Both complexes were found to be good homogeneous catalysts for the synthesis of a wide range of substituted thioethers and 5-substituted 1H-tetrazoles in 92% and 93% yield, respectively, at a low catalyst loading (0.5 mol%). The bond angles and distances, as discerned from the DFT calculations, commusurated with the experimental findings. The energy difference between the HOMO and the LUMO, calculated from DFT studies, was found to be 5.645 eV and 6.459 eV for complex 1 and complex 2, respectively. These results are in harmony with the observed higher catalytic activity of complex 1.

A series of 5-substituted-1H-tetrazoles have been efficiently synthesized in moderate to excellent yields (68–90%) under mild reaction conditions by combining aryl aldehydes, hydroxylamine hydrochloride with sodium azide in the presence of catalytic amoun

For the first time, metal-exchange in a magnetic metal–organic framework (MOF) via tandem magnetization and post-synthetic modification has been developed. The new magnetic mixed-metal metal–organic framework nanocomposite, CoFe2O4/[

The present invention relates to novel benzohydroxamic compounds of formula (I) and (II) and pharmaceutically acceptable salts, isomers and prodrugs thereof, exhibiting a high selective inhibitory activity against histone deacetylase 6 (HDAC6) enzyme.

5-Substituted 1 H -tetrazoles were effectively synthesized from aldoximes and diphenyl phosphorazidate (DPPA) under reflux conditions in xylenes. Various aldoximes underwent the cycloaddition reaction to afford the corresponding 5-substituted 1 H -tetrazoles in short reaction times and in good yields. Chiral aldoximes derived from amino acids also gave aminotetrazoles with almost no racemization.

An efficient protocol has been explored for the one-pot synthesis of tetrazole derivatives with wide functional group compatibility in moderate to very high yields starting from aliphatic and aromatic substituted aldehydes. The reaction proceeds via non-isolated oxime and nitrile intermediates. The structures of the products were confirmed by IR and NMR spectroscopy. A plausible reaction mechanism is also provided.

A versatile, robust and efficient strategy for the synthesis of vast range of highly functionalized 5-substituted 1H-tetrazole derivatives by using one pot three-component synthesis from various aldehydes, hydroxylamine hydrochloride and sodium azide in p

Background: In previous reports, the antibacterial properties of certain tetrazole derivatives have been described. We have previously reported the antibacterial properties of aryl 1H-tetrazole compounds. Objective: To study the antibacterial activity of 5-substituted heteroaryl, vinyl, benzyl, and alkyl 1H-tetrazole derivatives. Methods: The antibacterial properties of heteroaryl, vinyl, benzylic, and aliphatic tetrazole derivatives were investigated against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The activity was assessed by determining the minimum inhibitory concentration of these tetrazole derivatives and comparing them to the known antibiotics amoxicillin, trimethoprim and sulfamethoxazole. Results: The tetrazole compounds were prepared utilizing cerium(III) chloride heptahydrate catalysis at 160o C for 1-4 h in a microwave reactor using an aqueous solvent mixture. The most active derivatives exhibited minimum inhibitory concentration values between 125-250 μg/mL against Escherichia coli. More importantly, these compounds were considerably more active when used in combination with trimethoprim and a significant synergistic effect was observed (MIC = 0.98-7.81 μg/mL) against E. coli and S. aureus. Conclusion: The tetrazole derivatives were synthesized in high yield and short reaction times in water. Several of the tetrazole compounds showed a significant synergistic antibacterial effect when used with trimethoprim.

The search for a faster, safer protocol for the direct synthesis of 5-aryltetrazoles from aryl nitriles in the presence of sodium azide and an amine hydrochloride salt led to the discovery of a buffered system comprised of BnNH2, BnNH2·HCl, and NaN3. After optimization of reaction conditions and a thorough investigation of reaction safety, the procedure was demonstrated for the synthesis of several hundred grams of 4-chloro-2-(2H-tetrazol-5-yl)phenol. The generality of the developed reaction conditions was established by a small-scale reactivity screen using 16 additional aryl and heteroaryl nitrile substrates.

A simple and efficient protocol developed for the synthesis of 5-substituted 1H-tetrazole derivatives through [2+3] cycloaddition reaction between benzonitriles and sodium azide using diisopropylethylammonium acetate as a recyclable reaction medium is described. The reactions proceed well at 80 °C and provide the corresponding tetrazoles in good to excellent yields (up to 94% yield). Developed method has notable advantages, such as simple and mild conditions, easy workup, reusability with consistent catalytic activity, and safer alternative to hazardous, corrosive conventional Lewis acid catalysts.

The [3+2] cycloaddition between various nitriles and sodium azide proceeds smoothly in the presence of a new CuII catalyst in N-methyl-2-pyrrolidone (NMP) to give the corresponding 5-substituted 1H-tetrazoles. The desired tetrazoles were obtain

A novel method for the synthesis of 5-substituted 1H-tetrazoles using diphenyl phosphorazidate (DPPA) has been developed. Aromatic and aliphatic aldoximes underwent cycloaddition to afford the corresponding 5-substituted 1H-tetrazoles with ease and efficiency.

A simple and efficient protocol has been developed for the synthesis of 5-substituted 1H-tetrazole derivatives in good to excellent yields from various oximes and sodium azide by using indium(III) chloride as a Lewis acid catalyst. The present method has

A new heterogeneous and reusable polyvinyl alcohol immobilized copper(ii) Schiff base complex (PVA@Cu(ii) Schiff base complex) was synthesized in water, characterized and used for the highly efficient environmentally benign one-pot three-component prepara

A simple and efficient procedure for the synthesis of 5-substituted 1H-tetrazole derivatives has been developed using a one-pot, three-component reaction of various aldehydes, hydroxylamine and sodium azide in the presence of a catalytic amount of Cu-MCM-41, as a nanostructured, heterogeneous and reusable catalyst. In this research, Cu-MCM-41 nanoparticles with three Cu/Si molar ratios were prepared and characterized using various techniques. The characterization and optimization results show that the catalyst with a Cu/Si molar ratio of 0.050 has the best catalytic activity.

(Chemical Equation Presented). Bismuth chloride was used to catalyze the [2 + 3] cycloaddition between sodium azide with aryl nitriles, aliphatic nitriles, and vinyl nitriles. A number of 5-substituted 1H-tetrazoles were synthesized in water or isopropano

An efficient method is developed for the synthesis of 5-substituted 1H-tetrazoles through the [3 + 2] cycloaddition reaction of nitriles with sodium azide using silver(I) bis(trifluoromethanesulfonyl)imide (AgNTf2) as a catalyst. This procedure provides mild reaction conditions, short reaction times and high yields.

A strategy for the synthesis of 5-substituted 1H-tetrazoles from various (E)-aldoximes and sodium azide was adopted using copper ferrite nanoparticles as a reusable catalyst.

A simple and efficient protocol is developed for the synthesis of 5-substituted 1H-tetrazole derivatives from various nitriles and sodium azide (NaN3) via [3+2] cycloaddition reaction using B(C6F 5)3 as a catalyst. The present synthetic method displayed significant advantages such as low catalyst loading, mild reaction conditions, low toxicity, easy work-up, high yields, and compatibility with other functional groups.

A novel and metal free catalysis of synthesizing 5-substituted 1H-tetrazoles through 1,3-dipolar cycloaddition of boron-azides and nitriles is reported with broad substrate scope and excellent yields.

The mechanism of the azidea-nitrile cycloaddition mediated by different Bronsted and Lewis acids has been addressed through DFT calculations. In all cases activation of the nitrile substrate by the Bronsted or Lewis acid catalyst was found to be responsib

A series of 5-substituted 1H-tetrazoles were synthesized through [3+2] cycloaddition reactions between nitriles RCN and NaN3 in the presence of Cu-Zn alloy nanopowder as catalyst. The 1,5-dibutyl, 1-butyl-5-hexyl, 2,5-dibutyl, and 2-butyl-5-hexyl derivatives were then used as building blocks to synthesize several novel tetrazolium ionic liquids (ILs) with EtSO 4-, OTf-, and NTf2- counterions. Whereas alkylation of the 2,5-dialkyltetrazoles selectively gave the N-4 alkylated onium salts, with the 1,5-dialkyl derivatives approximately 1:1 mixtures of two tetrazolium salts were formed by alkylation at N-3 and N-4. The triflate and ethyl sulfate salts are room-temperature ILs that are hydrophilic, whereas the NTf2 salts are low-melting ILs and are hydrophobic. The resulting tetrazolium-based ionic liquids were studied by various multinuclear and 2D NMR techniques including natural abundance 15N and 1H/15N correlations.

An easy access to various 5-aryl-1H-tetrazoles by a one-pot direct conversion of aldehydes to tetrazoles without the isolation of the intermediate nitriles using commercially available iodine as a catalyst is described. The protocol offers advantages in terms of good yields, mild reaction conditions, short reaction times, and use of readily available environmentally compatible catalyst. Copyright

A simple, efficient and a versatile method for the synthesis of 5-substituted-1H-tetrazoles by a [3+2]-cycloaddition reaction of arylnitriles with sodium azide in DMF using ZrOCl2.8 H2O as catalyst has been developed. The reactions work well at 100°C and give the desired products in excellent yield. The examples studied include arylnitriles having electron donating as well as electron releasing groups on the arene nucleus. Indian Academy of Sciences.

The mechanism of the azide-nitrile cycloaddition mediated by the known dialkylltin oxide-trimethylsilyl azide catalyst system has been addressed through DFT calculations. The catalytic cycle for this tin/silicon complex-based mechanism has been thoroughly examined, disclosing the most plausible intermediates and the energetics involved in the rate enhancement. In addition, a new catalyst, 5-azido-1-methyl-3,4-dihydro-2H-pyrrolium azide, is presented for the formation of tetrazoles by cycloaddition of sodium azide with organic nitriles under neutral conditions. The efficiency of this organocatalyst, generated in situ from N-methyl-2-pyrrolidone (NMP), sodium azide, and trimethylsilyl chloride under reaction conditions, has been examined by preparation of a series of 5-substituted-1H-tetrazoles. The desired target structures were obtained in high yields within 15-25 min employing controlled microwave heating. An in depth computational analysis of the proposed catalytic cycle has also been addressed to understand the nature of the rate acceleration. The computed energy barriers have been compared to the dialkylltin oxide-trimethylsilyl azide metal-based catalyst system. Both the tin/silicon species and the new organocatalyst accelerate the azide-nitrile coupling by activating the nitrile substrate. As compared to the dialkylltin oxide-trimethylsilyl azide method, the organocatalytic system presented herein has the advantage of higher reactivity, in situ generation from inexpensive materials, and low toxicity.

Harnessing hydrazoic acid in a microreactor! Tetrazoles have been synthesized in a very efficient manner by using a high-temperature/high-pressure process intensification regime. Despite the toxic and explosive nature of hydrazoic acid, the synthesis was conducted safely in continuous flow format with residence times as short as 2.5 minutes at 260□°C (see picture).

The [3+2] cycloaddition reaction between sodium azide and various organic nitriles proceeds smoothly in the presence of amine salts as catalyst in dimethylformamide. The corresponding 5-substituted 1-H tetrazoles were obtained under mild condition in good to excellent yields. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file. Taylor & Francis Group, LLC.

We have reported that Amberlite IRA900F (Amb-F) is an efficient metal-free catalyst for the activation of Si-N and Si-O bonds and a mild base in a variety of organic transformations under solvent-free conditions, such as the addition of TMSN3 to (E)-2-aryl-1-cyano-1-nitroethenes, nitriles, α,β-unsaturated acids and their esters, and the addition of dimethylsilyl ketene acetal and ethyl nitroacetate to β-nitrostyrenes. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

(Chemical Equation Presented) A series of primary alcohols and aldehydes were treated with iodine in ammonia water under microwave irradiation to give the intermediate nitriles, which without isolation underwent [2 + 3] cycloadditions with dicyandiamide and sodium azide to afford high yields of the corresponding triazines and tetrazoles, including the α-amino- and dipeptidyl tetrazoles in high optical purity.

A variety of novel heterocyclic compounds were synthesized and evaluated for MMP inhibition. Broad spectrum inhibition of MMPs 1, 2, 9, and 12 was found with pyridinone-based compounds while N-heterocyclic triazoles and tetrazoles were largely ineffective. A highly selective tetrazole inhibitor for MMP-2 was discovered.

Cheap and safe: Conventional methods to prepare tetrazoles employ dangerous, toxic reagents. A new route to these heterocycles (see scheme) uses inexpensive and nontoxic dialkyl aluminum azides. The cycloaddition occurs under mild conditions and tolerates a variety of functional groups. The low cost and ecocompatibility make this process attractive for large-scale preparation. (Chemical Equation Presented).

Racemic 5-aryl- and 5-(arylmethyl)tetrazolyl-substituted pyroaminoadipic and pipecolic acid derivatives were diastereoselectively synthesized from dimethyl meso-2,5-dibromoadipate (1) in good yields under mild reaction conditions. The key step of this reaction sequence is the selective N2-alkylation of 5-substituted tetrazoles with 1. The reactive 2-bromo-5-tetrazolyladipate derivatives 2a-g were generated and treated with sodium azide, followed by Pd/C-catalyzed hydrogenation, to provide lactams 4a-g. The chemoselective reduction of the amide carbonyl group of 4a-g with BH 3, followed by acid hydrolysis, provided 5-tetrazolylpipecolic acids in racemic form. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Tetrabutylammonium fluoride (TBAF) is an efficient catalyst in the [3 + 2] cycloaddition reaction of organic nitriles 1 with trimethylsilyl azide (TMSN3) in solventless conditions. The corresponding 5-substituted 1H-tetrazoles 2 were obtained under mild conditions and in 80-97% yields.

A variety of aldehydes reacted with iodine in ammonia water at room temperature to give the nitrile intermediates, which were trapped by addition of hydrogen peroxide, sodium azide, or dicyandiamide to produce their corresponding amides, tetrazoles, and 1,3,5-triazines in modest to high yields. The one-pot tandem reactions were conducted in water media, and the products were obtained simply by extraction or filtration.