An efficient hydration of nitriles with ruthenium-supported heterogeneous catalyst in water under moderate conditions

Ubiquitous Role of Phosphine-Based Water-Soluble Ligand in Promoting Catalytic Reactions in Water

Catalysis has been at the forefront of the developments that has revolutionised synthesis and provided the impetus in the discovery of platform technologies for efficient C-C or C-X bond formation. Current environmental situation however, demands a change in strategy with catalysis being promoted more in solvents that are benign (Water) and for that the development of hydrophilic ligands (especially phosphines) is a necessity which could promote catalytic reactions in water, allow recyclability of the catalytic solutions and make it possible to isolate products using column-free techniques that involve lesser usage of hazardous organic solvents. In this review, we therefore critically analyse such catalytic processes providing examples that do follow the above-mentioned parameter.

Fe3O4@SiO2@KIT-6@2-ATP@CuI as a catalyst for hydration of benzonitriles and reduction of nitroarenes

In this paper, a new type of magnetic mesoporous material (Fe₃O₄@SiO₂@KIT-6@2-ATP@Cu^I) was designed and synthesized and its application in the synthesis of amides and anilines was investigated. The structure of Fe₃O₄@SiO₂@KIT-6@2-ATP@Cu^I was characterized and identified using FTIR, SEM, XRD, TGA, BET, VSM, and ICP techniques. An external magnet can easily remove the synthesized catalyst from the reaction medium, and be reused in several consequence runs.

Ag-embedded manganese oxide octahedral molecular sieve (Ag-OMS-2) nano-rods as efficient heterogeneous catalysts for hydration of nitriles to amides in aqueous solution

Silver-embedded manganese oxide octahedral molecular sieve (Ag-OMS-2) nano-rods were synthesized using a pre-incorporation approach, and unambiguously characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). A highly uniform distribution of Ag nanoparticles embedded in the porous structure of OMS-2, was found to be in favor of high catalytic activity of the composite for hydration of nitriles to corresponding amides in aqueous solution. By using a catalyst dosage of 30 mg per mmol of substrate, in the temperature range of 80-100 °C, and reaction times of 4-9 h, excellent yields (73-96%) of the desired amides (13 examples) were obtained. Also, the catalyst was easy to recycle, and showed a slight decrease in efficiency after six consecutive runs.

Hydration of Nitriles Catalyzed by Ruthenium Complexes: Role of Dihydrogen Bonding Interactions in Promoting Base-Free Catalysis

Ru(II) complexes of amide-phosphine-based tridentate ligands additionally containing pyridine, isoquinoline, and quinoline rings have been synthesized, and their catalytic utility for the selective hydration of nitriles to amides is explored under the base-containing as well as base-free conditions. The chloride-ligated complexes 1-3 exhibited significant catalytic activity in the presence of a base, whereas hydride-ligated complexes 4-6 carried out the hydration of nitrile without the requirement of any base. The mechanistic studies revealed the involvement of [Ru-H] species as the active catalyst in the catalytic cycle. The [Ru-H] species assisted in the polarization of an incoming water molecule through [Ru-H···H-OH] dihydrogen bonding interaction and consequently aided in the attack of a positioned water molecule to a nitrile coordinated to a ruthenium center. Substrate binding studies and kinetic experiments further supported the mechanism. A wide variety of aromatic nitriles containing both electron-withdrawing and electron-releasing groups as well as other substrates including aliphatic nitriles, base-sensitive nitriles, and a few biologically relevant nitriles were employed for the selective hydration.

Single-Step Fabrication and Characterization of Nanoscale Cu Thinfilms for Optoelectronic Applications

Nanostructured materials with optical transmittance with sufficient electrical conductivity are feasible for the transparent electrical devices and optoelectronic applications. Copper (Cu) possesses inherent superior electrical conductivity. Cu thin films on glass substrates provide the basic design understanding of the transparent electrodes for humidity sensors and solar cells applications. To understand the fundamental fabrication and electrical properties, a single-step facile fabrication approach was applied for Cu nanofilms through the DC sputtering method. Correlation of thickness of Cu nanofilms with optical and electrical properties was established. Parameters such as current, voltage, vacuum pressure, and time of coating were varied to develop different thickness of metal coating. Under optimized conditions of 10−1 torr vacuum, 1.45 KV voltage, and 4–6 min coating time, a conductive path is successfully established. A 1 min coated sample demonstrated resistance of 4000 ohm and conductance of a 6 min coated sample was raised to 56 m-mho. A higher surge of voltage assisted the production of relatively thick and uniform coatings with the crystallite size of 12 nm. The average coating thickness of 19.8 nm and roughness of 4.5 nm was obtained for a 5 min coated sample through AFM analysis. Further, it was observed that uniform nanostructured coating is essential to establish a mean free path of coated particles.

High-throughput screening for distinguishing nitrilases from nitrile hydratases in Aspergillus and application of a Box-Behnken design for the optimization of nitrilase

Nitrilases and nitrile hydratases/amidases hydrolyze nitriles into carboxylic acids and/or amides, which are used in industrial chemical processes. In the present study, 26 microorganisms, including yeasts and filamentous fungi, in a minimum solid mineral medium supplemented with glucose and phenylacetonitrile were screened to evaluate their biocatalytic potential. Of these microorganisms, five fungi of the genus Aspergillus were selected and subjected to colorimetry studies to evaluate the production and distinction of nitrilase and nitrile hydratase/amidase enzymes. Aspergillus parasiticus Speare 7967 and A. niger Tiegh. 8285 produced nitrilases and nitrile hydratase, respectively. Nitrilase optimization was performed using a Box-Behnken design (BBD) and fungus A. parasiticus Speare 7967 with phenylacetonitrile volume (μl), pH, and carbohydrate source (starch:glucose; g/g) as independent variables and nitrilase activity (U ml^-1 ) as dependent variable. Maximum activity (2.97 × 10^-3  U ml^-1 ) was obtained at pH 5.5, 80 μl of phenylacetonitrile, and 15 g of glucose. A. parasiticus Speare 7967 showed promise in the biotransformation of nitriles to carboxylic acids.