Efficient synthesis of arylaminotetrazoles in water

Greener Synthesis of Nitrogen-Containing Heterocycles in Water, PEG, and Bio-Based Solvents

The solvents used in chemistry are a fundamental element of the environmental performance of processes in corporate and academic laboratories. Their influence on costs, health safety, and nature cannot be neglected. Quantitatively, solvents are the most abundant constituents of chemical transformations; therefore, acting on solvents and replacing standard solvents with safer products can have a great ecological impact. However, not all green solvents are suitable for the wide scope of organic chemistry reactions. A second point to consider is that 50% of pharmaceutical drugs are nitrogen heterocycles compounds. It therefore appeared important to provide an overview of the more ecological methodologies for synthesizing this class of compounds. In this review, all publications since 2000 that describe green reactions leading to the formation of nitrogen heterocycles using safe solvents were considered. We chose water, PEG, and bio-based solvents for their negligible toxicity. The synthesis of five-, six-, and seven-membered aromatic nitrogen heterocycles using green reactions reported in the literature to date is described.

Magnetic chitosan-copper nanocomposite: A plant assembled catalyst for the synthesis of amino- and N-sulfonyl tetrazoles in eco-friendly media

A greener, cost efficient and simple method is described to prepare copper nanoparticles (NPs) immobilized on the magnetic chitosan (one of the more versatile polysaccharides) using Euphorbia falcata leaf extract as reducing/stabilizing agent. The prepared catalyst (Cu NPs@Fe₃O₄-chitosan) was authenticated by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetry/derivative thermogravimetry (TG/DTG), Vibrating sample magnetometer (VSM), and elemental mapping. TEM analysis indicates that Cu NPs with average sizes in 5-10 nm range is formed on magnetic chitosan with the spherical morphology. The Cu NPs@Fe₃O₄-chitosan was employed as a new catalyst for the synthesis of different tetrazoles by the reaction of various secondary or tertiary cyanamides with sodium azide in water under reflux conditions. Easy separation by external magnetic field, mild reaction conditions, low cost and the reusability are some of the beneficial features of this catalyst.

Green synthesis of Ag/Fe(3)O(4) nanocomposite using Euphorbia peplus Linn leaf extract and evaluation of its catalytic activity

In this work, the Ag/Fe₃O₄ nanocomposite was prepared by Euphorbia peplus Linn (L.) leaf extract as a suitable reducing source and stabilizing agent. The green synthesized nanocomposite was characterized using X-ray diffraction analysis (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) images, energy-dispersive X-ray spectroscopy (EDS) and FT-IR spectroscopy. TEM analysis of Ag/Fe₃O₄ nanocomposite showed the spherical shape nanoparticles (NPs) with an average size of 5-10nm. The Ag/Fe₃O₄ nanocomposite then was used as a magnetically recoverable catalyst for the [2+3] cycloaddition of arylcyanamides and sodium azide in high yields and short reaction times without formation of hydrazoic acid (HN₃). Also it can be easily recovered via applying of external magnetic field and reused several times without significant loss of activity.

A review of syntheses of 1,5-disubstituted tetrazole derivatives

This report provides a brief overview of the various representative literature procedures for the synthesis of 1,5-disubstituted tetrazoles (1,5-DSTs) and fused 1,5-disubstituted tetrazoles with more than 120 references. Most of the published methods for the synthesis of 1,5-DSTs include the use of nitriles, amides, thioamides, imidoyl chlorides, heterocumulenes, isocyanates, isothiocyanates, carbodiimides, ketenimines, ketones, amines, and alkenes as the starting materials. The transformation of 1- and 5-substituted tetrazoles into 1,5-DSTs is also covered in this report.

Copper Iodide Nanoparticles-Catalysed Cyanation of Aryl Halides Using Non-Toxic K4[Fe(CN)6] in the Presence of 1,2-Bis(5-Tetrazolyl)Benzene as an Efficient Ligand

Cyanation of aryl bromides were carried out with K4[Fe(CN)6] in the presence of catalytic amounts of a copper salt and 1,2-bis(5-tetrazolyl)benzene as a ligand under thermal conditions. This method has the advantages of high yields, simple methodology and easy work up.

CoFe2O4 Nanoparticles as a Magnetically Recoverable and Reusable Catalyst for the Synthesis of Arylaminotetrazoles and 5-aryloxytetrazoles

An efficient and direct method is described for the synthesis of 5-arylamino-1 H-tetrazoles (Isomer A) or 1-aryl-5-amino-1 H-tetrazoles (Isomer B) and 5-aryloxytetrazoles from arylcyanamides or cynates with nano CoFe2O4 as a reusable and efficient heterogeneous catalyst. Isomer A was obtained from arylcyanamides carrying electron-withdrawing substituents on the aryl ring, while isomer B was produced with electron-releasing groups. The significant advantages of this methodology are high yields, elimination of dangerous and harmful hydrazoic acid, simple work-up procedure and the recovery and reusability of the catalyst.

Electrochemical and DFT study on the inhibition of 316L stainless steel corrosion in acidic medium by 1-(4-nitrophenyl)-5-amino-1H-tetrazole

This article describes the best corrosion inhibition behavior and adsorption of newly synthesized amino tetrazole using electrochemical and computational methods.

Solvent-Free Synthesis of 1-Aryl-1H-1,2,3,4-Tetrazoles using FeCl3–SiO2 Catalysis under Conventional and Ultrasound Irradiation Conditions

1-Aryl-1 H-1,2,3,4-tetrazoles were synthesised by the solvent-free reactions of aryl amines, sodium azide and triethyl orthoformate using FeCl3–SiO2 as an effective heterogeneous catalyst under conventional and ultrasound irradiation conditions. This method has the advantages of high yields, simple methodology and easy work-up. The catalyst can be recovered by simple filtration and reused delivering good yields.

Synthesis of 1,4-Dihydropyridines Bearing a Carbamate Moiety on the 4-Position

A good range of 1,4-dihydropyridines bearing a carbamate moiety on the 4-position were synthesized from the primary reaction of different hydroxyaldehydes with phenyl isocyanates and the subsequent reaction of the obtained carbamates with methyl acetoacetate in the presence of ammonium fluoride. When phenyl isothiocyanate was used in place of phenyl isocyanate in the same condition, the reaction did not take place.

Silica Sulfuric Acid as an Efficient Heterogeneous Catalyst for the Solvent-Free Synthesis of 1-Substituted 1H-1,2,3,4-Tetrazoles

Silica sulfuric acid (SSA) was found to be an efficient heterogeneous catalyst for the synthesis of 1-substituted 1H-1,2,3,4-tetrazoles from the reaction of primary amines with triethyl orthoformate and sodium azide under thermal and solvent-free conditions.

Tandem regioselective synthesis of tetrazoles and related heterocycles using iodine

A one-pot, tandem process has been developed for the synthesis of a library of tetrazoles from aryl isothiocyanates. Condensation of aryl isothiocyanates with ammonia, and aryl amines (R-NH(2)) provided mono, 1,3-disubstituted symmetrical and unsymmetrical thioureas, which on desulfurization with molecular iodine (I(2)) led to formation of the corresponding heterocumulene (cyanamides or carbodiimides). The in situ generated heterocumulene on subsequent treatment with sodium azide at room temperature gave corresponding tetrazoles. The product regioselectivity for unsymmetrical 1,3-disubstituted thioureas was found to be correlated with the basicities (pK(a)'s) of the parent amines attached to the thiourea. Aryl-sec-alkyl unsymmetrical thioureas gave thioamido guanidino products rather than the 5-aminotetrazoles produced by HgCl(2) mediation of the reaction. Bis-thioureas derived from aryl isothiocyanates and hydrazine gave thiadiazoles exclusively.