Silica-supported Fe/Fe–O nanoparticles for the catalytic hydrogenation of nitriles to amines in the presence of aluminium additives

The hydrogenation of nitriles to amines represents an important and frequently used industrial process due to the broad applicability of the resulting products in chemistry and life sciences. Despite the existing portfolio of catalysts reported for the hydrogenation of nitriles, the development of iron-based heterogeneous catalysts for this process is still a challenge. Here, we show that the impregnation and pyrolysis of iron(II) acetate on commercial silica produces a reusable Fe/Fe–O@SiO2 catalyst with a well-defined structure comprising the fayalite phase at the Si–Fe interface and α-Fe nanoparticles, covered by an ultrathin amorphous iron(III) oxide layer, growing from the silica matrix. These Fe/Fe–O core–shell nanoparticles, in the presence of catalytic amounts of aluminium additives, promote the hydrogenation of all kinds of nitriles, including structurally challenging and functionally diverse aromatic, heterocyclic, aliphatic and fatty nitriles, to produce primary amines under scalable and industrially viable conditions.

A Facile Synthesis of substituted Trifluoromethyl piperidines with diversify functionalization

: Piperidine-based alkaloids are undoubtedly an important class of biologically active natural products. When a unique group like trifluoromethyl (Tfm) is added to an active compound, it significantly ameliorates its bioactivity, bioavailability, physical and chemical properties. Many fluorination and trifluoromethylation methods have been reported. In the present paper, we have shown that among all other trifluoromethylation pathways, Mannich reaction also has the great tendency to introduce a Tfm group in a saturated or aromatic heterocyclic compound. Applications of this reaction are elaborated in preparing several derivatives of piperidine base alkaloids with trifluoromethyl at α-position. Furthermore, the substitution at C-4 and C-6 was successfully achieved with variety of saturated and aromatic groups.

Applications of Metal Complexes Dyes in Analytical Chemistry

Trace elements, especially heavy metals, are considered to be one of the main sources of pollution in the environment since they have a significant effect on ecological quality. Commonly, the analytical methods for the determination of trace metals are the spectrometry techniques. While, the electroanalytical methods are recognized as a powerful technique for trace metals owing to its remarkable sensitivity, relatively inexpensive instrumentation, ability for multi-element determination at trace and ultra trace level. New alternative electrode materials are highly desired to develop sensitive stripping sensors for meeting the growing demands for on-site environmental monitoring. Dyes aromatic heterocyclic compound, used in food, textile and cosmetic industries has been used for spectrophotometric determination of metals. In electrochemitry, methods for metals determination based on their complexation with dyes were proposed. In this chapter, a brief summary of spectrometry methods and electrochemical sensors for heavy metals detection based on the formation of metals dyes complexes is presented.

Acidic Stabilization of the Dual-Aromatic Heterocyclic Anions

Recently, we discovered that the delocalization of nitrogen lone-pair electrons (NLPEs) in five-membered nitrogen heterocycles created a second σ-aromaticity in addition to the prototypical π-aromaticity. Such dual-aromatic compounds, such as the pentazole anion, were proved to have distinct chemistry in comparison to traditional π-aromatics, such as benzene, and were surprisingly unstable, susceptible to electrophilic attack, and relatively difficult to obtain. The dual-aromatics are basic in nature, but prefer not to be protonated when confronting more than three hydronium/ammonium ions, which violates common sense understanding of acid−base neutralization for a reason that is unclear. Here, we carried out 63 test simulations to explore the stability and reactivity of three basic heterocycle anions (pentazole anion N5¯, tetrazole anion N4C1H1¯, and 1,2,4-triazole anion N3C2H2¯) in four types of solvents (acidic ions, H3O+ and NH4+, polar organics, THF, and neutral organics, benzene) with different acidities and concentrations. By quantum mechanical calculations of the electron density, atomistic structure, interatomic interactions, molecular orbital, magnetic shielding, and energetics, we confirmed the presence of dual aromaticity in the heterocyclic anions, and discovered their reactivity to be a competition between their basicity and dual aromaticity. Interestingly, when the acidic ions H3O+/NH4+ are three times more in number than the basic heterocyclic anions, the anions turn to violate acid−base neutralization and remain unprotonated, and the surrounding acidic ions start to show a significant stabilization effect on the studied heterocyclic anions. This work brings new knowledge to nitrogen aromatics and the finding is expected to be adaptable for other pnictogen five-membered ring systems.

Imidazole Scaffold based Compounds in the Development of Therapeutic Drugs

: Imidazole has an important five-membered aromatic heterocyclic ring, which is available widely in natural products and synthetic molecules. The special structural characteristics of imidazole ring enable it to bind with various enzymes and receptors through hydrogen bonds, coordination, ion-dipole and cation-π interactions, hydrophobic effects, and Van der Waals forces. These interactions promote several biological activities involving anti-tumor, anti-inflammatory, anti-microbial and anti-viral properties. Herein, we review and discuss the recent developments occurred in using imidazole derivatives along with their special pharmacological activities for various diseases treatment.

Crown ethers for the synthesis of heterocycles

: Heterocyclic compounds are the largest and most diverse family of organic compounds. Among them, aromatic heterocyclic compounds are the structural motifs found in many biologically active synthetic and natural compounds, agrochemicals, and medicines. Moreover, aromatic heterocyclic compounds are extensively utilized to form dyes and polymeric materials of great importance. In organic synthesis, there are several reports on the uses of aromatic heterocyclic compounds as intermediates. In this review article, we have focused on the synthesis of heterocycles using crown ethers.

An Efficient One Pot, Multicomponent Synthesis of 1, 3-Thiazolidin-4-Ones Using L-Proline as Catalyst in Water

: An efficient methodology for the synthesis of 1,3-thiazolidin-4-ones using L-Proline as catalyst under aqueous conditions has been developed. The one-pot, multicomponent reaction of aromatic/heterocyclic aldehyde, aromatic amine and thioglycolic acid at room temperature give 1,3-thiazolidin-4-ones in moderate to good yields. Further, the current approach is notably greener than traditional methods with E-factor of 3.1 and the eco scale score of 96. The developed protocol offers several features, such as being simple, environmentally benign, energy-efficient, economical, mild conditions, shorter reaction time.