Catalytic Reduction Of Nitroarenes Research Articles

Catalytic reduction of nitroarenes by Cucumis maderaspatanus L. leaves extract mediated silver nanoparticles

BackgroundIn a variety of applications, silver exhibits a very high potential, especially when it takes the form of nanoparticles. The environmentally friendly green synthesis of metal nanoparticles is growing in popularity due to the affordability and abundance of plant materials, with the aim to reduce the harmful chemicals and the cost involved in the synthesis of nanoparticles. MethodologyThe Cucumis maderaspatanus L. (CmL.) leaves extract was used to synthesize silver nanoparticles (Cm-Ag NPs). The Cm-Ag NPs were confirmed by UV–vis, XRD, FE-SEM, FT-IR, XPS, TEM with EDAX, zeta potential, TGA, and BET analysis. The efficacy of Cm-Ag NPs was tested on the reduction of different aromatic nitroarenes using sodium borohydride (NaBH4) as a reducing agent. The reduction reactions were followed by varying the concentration of nitroarenes [0.5 × 10−4 M to 1.5 × 10−4 M], NaBH4 [1 × 10−3 M to 10 × 10−3 M], and Cm-Ag NPs [5 mg to 25 mg]. Significant findingsThe surface plasmon resonance at 442 nm has been attributed to the Cm-Ag NPs formation. FT-IR peaks confirmed the reducing and capping potential of Cucumis maderaspatanus L. leaves extract. The XRD result showed the Cm-Ag NPs are crystalline and the size was calculated as 31.57 nm. FE-SEM analysis exhibited the Cm-Ag NPs as spherical; the TEM image also indicated spherical Cm-Ag NPs with an average particle size of 15.85 nm. The EDAX analysis showed a strong signal at 3 KeV confirming the metallic Ag and XPS confirmed Agº. The higher stability of Cm-Ag NPs and the existence of phytoconstituents were shown by the zeta potential value –17.6 mV. The surface area of the nanoparticles was calculated to be 14.96 m2/g using BET. The reduction reactions followed pseudo-first-order kinetics. Cm-Ag NPs can be proposed as a catalyst for eliminating harmful pollutants.

Excellent chemoselective hydrogenation of nitroaromatics and unsaturated aldehyde at the confined silver nanospace

Catalytic reduction of nitroarenes and unsaturated aldehydes to corresponding hydrogenated products is an environment-friendly technology to prepare industrially important intermediates. however, high chemoselectivity still remains a big challenge when a nitroarene or unsaturated aldehyde molecule with two or more reducible groups. Herein, we construct a novel confined catalyst by encapsulating Ag NPs into the nanospace of hierarchical hollow silica (SiO2-Ag@void@SiO2), enabling the excellent chemoselective hydrogenation (>99%) of 2-nitrochlorobenzene and cinnamyl aldehyde into corresponding amino groups (-NH2) and hydroxyl groups (-OH) without hydrogenating other functional groups (-Cl and CC). The unique hydrogenation performance is identified to be associated with the confinement effect and highly dispersed Ag NPs because hydrogenation reaction takes place within the confined silver nanospace. Therefore, our study provides a guide to construct highly active catalysts for chemoselective catalysis.

Very rapid synthesis of highly efficient and biocompatible Ag2Se QD phytocatalysts using ultrasonic irradiation for aqueous/sustainable reduction of toxic nitroarenes to anilines with excellent yield/selectivity at room temperature

There are many problems associated with the synthesis of nanocatalysts and catalytic reduction of nitroarenes - e.g., high temperatures, costs, long reaction/synthesis process times, the toxicity of chemicals/solvents, undesirable byproducts, the toxic/harmful wastes, low efficiency/selectivity, etc. This study represents an attempt to overcome these challenges. To this purpose, biocompatible and highly efficient Ag2Se quantum dots (QDs) catalysts with antibacterial activity were synthesized in a very rapid (30 sec, rt), simple, inexpensive, sustainable/green, and one-pot strategy in water using ultrasonic irradiation. Characterization of the QDs was performed using different techniques. UV–Vis absorption and fluorescence spectroscopic studies showed an absorption peak at 480–550 nm and a maximum emission peak around 675 nm, which confirmed the successful synthesis of Ag2Se QDs via the applied biosynthetic method. Subsequently, catalytic reduction of nitroarenes by them was carried out under safe conditions (H2O, rt, air atmosphere) in ∼ 60 min with excellent yield and selectivity (>99%). Their catalytic activity in the reduction of various toxic nitroarenes to aminoarenes under green conditions was investigated. Thus, a rapid and safe ultrasound-based method was employed to prepare stable and green Ag2Se QDs phyto-catalysts with unique properties, including exquisite monodispersity in shape (orthorhombic) and size (∼7 nm), air-stability, and good purity and crystallinity. Importantly, instead of various toxic chemicals, the plant extract obtained by rapid ultrasonic method (10 min, rt) was used as natural reducing, capping, and stabilizing agents. Moreover, antibacterial assays results showed that Ag2Se-QDs catalysts at low concentrations (ppm) have high activity against all tested bacteria, especially E. coli (MIC:31.25 ppm, MBC:125 ppm) which were significantly different from those of Fig extract (MIC = MBC:500 ppm). The data reflect the role of these bio-synthesized Ag2Se-QDs catalysts in the development of versatile and very safe catalysts with biomedical properties.

Fabrication of bimetallic Au–Pt NSs for the catalytic reduction of nitroarenes

Abstract This work is based on the preparation of Au–Pt NSs (Nano stars) @Au core, Au–Pt NSs@Au1Pt3 core, Au–Pt NSs@Au1Pt1 core, Au–Pt NSs@Au3Pt1 core and Au@Pt NCs (Nano cubes) by a seed-mediated synthesis route. The characterizations of the prepared bimetallic NSs and NCs were conducted with ultraviolet-visible spectroscopy, X-ray diffraction, transmission electron microscopy, and inductively coupled plasma optical emission spectroscopy. The catalytic activities of the prepared Au–Pt NPs for 2-nitrophenol (2NP), 3-nitrophenol (3NP), 4-nitrophenol (4NP), 2-nitroresorcinol (2NR), and 4-nitrocatchol (4NR) reduction have been investigated. The results evidently demonstrated that the superior catalytic activities of Au–Pt alloy nano-dendrites can be attributed to the metal–metal connection (synergy between Au and Pt) in the catalysts.

Catalytic reduction of nitroarenes and degradation of dyes at room temperature by an efficient NNN pincer palladium catalyst based on the magnetic amino-triazole-modified chitosan

In this study, a magnetic chitosan biosupport was synthesized and functionalized with a NNN pincer ligand to facilitate palladium immobilization. FT-IR, FE-SEM, EDX, XRD, VSM, ICP, BET, and TGA analyses were used to characterize the synthesized nanocomposite (Fe3O4@Triazole-CS@NNN-Pd). Then, its catalytic activity in the reduction of a wide variety of nitroaromatic compounds at room temperature was investigated using sodium borohydride as a reducing agent, as well as the degradation of three hazardous dyes, including Methylene Blue (MB), Methyl Orange (MO), and Rhodamine B (RhB). This technique is feasible due to its ease of purification, environmental friendliness, and high yield of product generation in a relatively short response time. The nanocatalyst is easily separated, recovered, and reused for numerous cycles without significantly degrading catalytic activity.

Catalytic reduction of nitroarenes and Suzuki-Miyaura reactions using Pd complex stabilized on the functionalized polymeric support

The significance of aromatic amines as crude substances in diverse applications has attracted extensive consideration in the field of economic procedures for the reduction of nitroarenes. Also, the formation of CarbonCarbon bond as a dominant step in the structure of complex molecules is an important phenomenon in chemical reactions. Improvements of eco-friendly methodologies for reduction process and CarbonCarbon bond formation have been noticeable. The present work represents through a capable heterogeneous Pd catalyst, the reduction of nitroarenes to the corresponding amines in the presence of N2H4 as a weak hydrogen donor reagent in the room temperature and solvent-free condition was progressed. In addition, several CC bond formations through Suzuki-Miyaura reaction using one-pot mixture containing aryl halide, arylboronic acid in the presence of Pd catalyst at refluxed condition proceeded. Furthermore, the reusability of Pd catalyst for both reduction and Suzuki reactions showed five successive runs without any significant loss in its activity.

Polymer microgels for the stabilization of gold nanoparticles and their application in the catalytic reduction of nitroarenes in aqueous media.

Polymer microgels containing a polystyrene core and poly(N-isopropylmethacrylamide) shell were synthesized in aqueous media following a free radical precipitation polymerization. Au nanoparticles were fabricated into the shell region of the core–shell microgels denoted as P(STY@NIPM) by the in situ reduction of chloroauric acid with sodium borohydride. Various characterization techniques such as transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV-visible) and Fourier transform infrared spectroscopy (FTIR) were used for the characterization of Au–P(STY@NIPM). The catalytic potential of Au–P(STY@NIPM) toward the reductive reaction of 4-nitrophenol (4NP) under various reaction conditions was evaluated. The Arrhenius and Eyring parameters for the catalytic reduction of 4NP were determined to explore the process of catalysis. A variety of nitroarenes were converted successfully into their corresponding aminoarenes with good to excellent yields in the presence of the Au–P(STY@NIPM) system using NaBH4 as a reductant. The Au–P(STY@NIPM) system was found to be an efficient and recyclable catalyst with no significant loss in its catalytic efficiency.

Azo(xy) vs Aniline Selectivity in Catalytic Nitroarene Reduction by Intermetallics: Experiments and Simulations

Intermetallic nanoparticles are promising catalysts in hydrogenation and fuel cell technologies. Much is known about the ability of intermetallic nanoparticles to selectively reduce nitro vs alkene, alcohol, or halide functional groups; less is known about their selectivity toward aniline vs azo or azoxy condensation products that result from the reduction of a nitro group alone. Because azo(xy)arenes bear promise as dyes, chemical stabilizers, and building blocks to functional materials but can be difficult to isolate, developing high surface area nanoparticle catalysts that display azo(xy) selectivity is desirable. To address this question, we studied a family of nanocrystalline group 10 metal (Pd, Pt)- and group 14 metal (Ge, Sn, Pb)-containing intermetallics─Pd2Ge, Pd2Sn, Pd3Sn2, Pd3Pb, and PtSn─in the catalytic reduction of nitroarenes. In contrast to monometallic Au, Pt, and Pd nanoparticles and ″random″ PdxSn1 – x nanoalloys, which are selective for aniline, nanoparticles of atomically precise intermetallic Pd2Ge, Pd2Sn, Pd3Sn2, and PtSn prefer an indirect condensation pathway and have a high selectivity for the azo(xy) products. The only exception is Pd3Pb, the most active among the intermetallic nanoparticles studied here, which is instead selective for aniline. Employing a novel application of molecular dynamics─based on machine learned potentials within a DeePMD framework─to heterogeneous catalysis, we are able to identify key reaction species on the different types of catalysts employed, furthering our understanding of the unique selectivity of these materials. By demonstrating how intermetallic nanoparticles can be as active yet more selective than other more traditional catalysts, this work provides new physical insights and opens new opportunities in the use of these materials in other important chemical transformations and applications.

Fabrication of palladium nanocatalyst supported on magnetic eggshell and its catalytic character in the catalytic reduction of nitroarenes in water

Aromatic nitro compounds, which have good solubility in water, are highly toxic and non-biodegradable are one of the most important industrial pollutants and have negative effects on human health, aquatic life and the environment. Therefore, the elimination of these harmful organic compounds has become an issue of great importance. For this, in this study we have developed a palladium nanocatalyst supported on Fe3O4-coated eggshell and characterized by FT-IR, XRD, XPS, FE-SEM, TG/DTG, BET, TEM and EDS techniques (Pd-Fe3O4-ES). Also, the quantitative analysis of Pd was determined using ICP-OES. The catalytic behavior of the designed Pd-Fe3O4-ES nanocatalyst was investigated against the catalytic reduction of several highly toxic nitro compounds using NaBH4 in water at room temperature. The progress of the reduction was followed using high performance liquid chromatography (HPLC). The catalytic studies revealed that the nitro compounds were converted into the desired amines by the Pd-Fe3O4-ES nanocatalyst using a very low dose of catalyst (15 mg) and short-duration reactions (81–360 s) in aqueous medium at ambient temperature. Furthermore, the Pd-Fe3O4-ES nanocatalyst showed good catalytic stability by retaining its activity after the fifth catalytic run.

Real-Time Monitoring of Aqueous Organic Reduction Reactions Using Ex Situ Fiber Optic Raman Spectroscopy

Here, we demonstrate the use of Raman spectroscopy for real-time monitoring and analysis of the reduction of nitroarenes and ketones in an aqueous medium using an external fiber optic probe. In one case, the catalytic reduction of nitroarenes using hydrazine hydrate and a nickel boron composite catalyst was studied by monitoring the disappearance of the distinct nitro stretching frequency at 1350 cm–¹. Quantitative Raman spectroscopic techniques showed that the aqueous reduction reaction proceeds with pseudo-first-order kinetics. The biphasic reduction of cyclic ketones by aqueous dimethylamine borane (DMAB) was also examined. A nonpolar carbonyl compound and aqueous DMAB were mixed and an external Raman probe monitored the loss of the starting material via the carbonyl stretch at 1713 cm–¹ in the top organic phase. We also found that saturated aliphatic carbonyl compounds were reduced much faster than α,β-unsaturated and aromatic carbonyl compounds. Additionally, DMAB was found to be unreactive toward epoxides and esters, allowing for selective reduction of aliphatic ketones. Density functional theory analysis suggests that carbonyl reduction occurred through a dissociation mechanism followed by a concerted hydride transfer pathway.

Catalytic Reduction of Nitroarenes and Suzuki-Miyaura Reactions Using Pd Complex Stabilized on the Functionalized Polymeric Support

Catalytic Reduction of Nitroarenes and Suzuki-Miyaura Reactions Using Pd Complex Stabilized on the Functionalized Polymeric Support

Iron oxide modified N-doped porous carbon derived from porous organic polymers as a highly-efficient catalyst for reduction of nitroarenes

Fabrication of cost-effective non-noble metal-based catalysts is significant for heterogeneous catalysis. Here, we prepared a porous organic polymer (POP) through the facile condensation of p-phenylenediamine with ferrocene carboxaldehyde, and then the ferrocene-functionalized POP material was carbonized under inert atmosphere, obtaining the γ-Fe2O3 nanoparticles (NPs) modified N-doped porous carbon catalyst (γ-Fe2O3/NPC). Various characterizations (such as XRD, BET, TEM and XPS etc.) indicated that the obtained γ-Fe2O3/NPC catalyst exhibits unique structural properties with uniformly dispersed γ-Fe2O3 species, porous morphology, and N-doped defective amorphous carbon. The γ-Fe2O3/NPC catalyst shows excellent activity in the catalytic reduction of nitroarenes with hydrazine hydrate as reductant. The synergistic effect between γ-Fe2O3 NPs and N-doped porous carbon improve the hydrazine hydrate adsorption and activation for active hydrogen atoms production, which is beneficial for nitroarenes reduction. Moreover, the γ-Fe2O3/NPC catalyst could be easily recycled by using a magnet and reused without obviously loss of catalytic activity. Therefore, this work should provide a useful platform for designing and fabricating stable non-noble metal NPs based catalysts derived from POP materials that have potential for various catalytic applications.

Ru single atoms and nanoparticles on carbon nanotubes as multifunctional catalysts.

In the last decade we have witnessed increasing interest in the production of renewable energy and value-added chemicals through sustainable and low-cost technologies where catalysts play a crucial role. Herein, we report the application of a Ru/CNT material containing a mixture of Ru single atoms and Ru nanoparticles as a multifunctional catalyst for both the catalytic reduction of nitroarenes and the electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The catalytic activity of the Ru-CNT material was evaluated in the reduction of 4-nitrophenol (4-NP), 4-nitroaniline (4-NA) and 2-nitrophenol (2-NP) in the presence of sodium borohydride as a reducing agent at room temperature, showing high catalytic activity with normalized rate constants (knor) of 19.0 × 103, 57.7 × 103 and 16.6 × 103 min-1 mmol-1 respectively. Furthermore, the catalyst could be reused in at least 10 cycles without catalytic activity loss, confirming the high stability and robustness of the material. The Ru/CNT material also showed good ORR electrocatalytic activity in alkaline medium with Eonset of 0.76 V vs. RHE, a diffusion-limited current density of 3.89 mA cm-2 and ñO2 of 3.3. In addition, Ru/CNT was remarkably insensitive to methanol with a current retention of 93% (51% for Pt/C) and competitive electrochemical stability of 80% after 20 000 s. Moreover, Ru/CNT was active for the OER with jmax = 29.5 mA cm-2 at E = 1.86 V vs. RHE, η10 = 0.50 V and good stability (η10 changed to 0.01 V and jmax only decreased by ≈12% after 500 cycles).

Synergistic effect of metal-organic framework-derived boron and nitrogen heteroatom-doped three-dimensional porous carbons for precious-metal-free catalytic reduction of nitroarenes

We report a scalable and controllable synthesis of metal-organic framework (MOF)-derived three-dimensional boron and nitrogen heteroatom-doped porous carbons (3D-BNPCs) and their synergistic effect for metal-free catalytic 4-nitrophenol (4-NP) reduction. The substitution of boron atoms into zeolitic imidazole framework-8 (ZIF-8)-derived nitrogen-doped porous carbon (B-NPC-1200) significantly improves the electrical conductivity and the catalytic 4-NP reduction. We propose the heteroatom-doping of boron, nitrogen and oxygen in the 3D- B-N PC catalysts creates synergistic effect on 4-NP reduction by creating more catalytically active sites. High-Resolution X-ray Photoelectron Spectroscopy (HR-XPS) and Density Functional Theory (DFT) calculations were carried out to confirm and investigate the role of active sites on adsorption of 4-NP molecules in B-NPC-1200. We find that the strongly active sites can only be created based on the synergistic effect between nitrogen, boron and oxygen atoms, and the increased density of the active sites are responsible for the lowering of the apparent activation energy in B-NPC-1200 structure. As synthesized B-NPC-1200 exhibits superior catalytic activities for 4-NP reduction with a low apparent activation energy of 27.0 kJ/mol and a high reaction rate constant of 2.3*10^−3 (s-1). The catalyst can run five times without decreasing significant catalytic activity. The reduction reactions of various nitroarene compounds have been further tested using the B-N PC-1200 material as the precious-metal-free catalyst.

Catalytic Reduction of Nitroarenes by Dipalladium Complexes: Synergistic Effect

The direct reaction between 2,7-bis(2-pyridinyl)-1,8-naphthyridine (bpnp) and Pd(CH3COO)2 in CF3COOH yields the new dinuclear palladium(II) complex [Pd2(bpnp)(μ-OH)(CF3CO2)2](CF3CO2) (1). Similarly, substitution of Pd(CH3CN)4(BF4)2 with bpnp in DMF gives [Pd2(bpnp)(μ-OH)(DMF)2](BF4)3 (2). Treatment of 1 or 2 with Cl– readily provide the chloro-substituted species [Pd(bpnp)(μ-OH)(Cl)2]+. All complexes were characterized by spectroscopic methods, and the structure of 2 was further confirmed by X-ray crystallography. Complex 1 is an efficient catalyst for the reduction of aromatic nitro compounds leading to the corresponding aniline derivatives under atmospheric pressure of hydrogen at 50 °C. The mechanistic pathway of the catalysis is investigated. From the reaction pathway, it is suggested that a facile condensation of nitroso and hydroxylamine intermediates is enabled by the dipalladium system and the desired transformation proceeds smoothly under mild reaction conditions to yield the reduced product.

Facile preparation of fluffy N-doped carbon modified with Ag nanoparticles as a highly active and reusable catalyst for catalytic reduction of nitroarenes

Novel fluffy smoke like mesoporous N-doped carbon (mNC) was prepared through a facile one-pot carbonization method using the low-cost melamine and polyacrylonitrile as the precursor materials. The obtained mNC material exhibits a high surface area, rich nitrogen content and can be used as an ideal catalyst support to fabricate noble metal modified nanocatalysts. Here, small Ag nanoparticles were supported on the mNC material with high dispersion to give the Ag/mNC nanocatalyst. The obtained Ag/mNC nanocatalyst was used in the catalytic reduction of nitroarenes and showed excellent catalytic activity, probably due to the small Ag NPs which highly dispersed on the fluffy mNC material that can enhance the accessibility and mass transfer, and subsequently enhance the catalytic activity. It is worth mentioning that, in the catalytic reduction of nitroarenes with halogenated groups, almost no dehalogenation phenomenon can be observed, which implies the superior catalytic chemoselectivity of the Ag/mNC nanocatalyst.

Magnetically Retrievable Modified Nickel Ferrite Nanoparticles: Efficient Catalytic Reduction of Nitroarenes and Photo-oxidation of Hazardous Dyes

Of recently, magnetic nano-ferrites have come forward as excellent catalysts for various organic transformations and mitigation of environmental deterioration. In the present investigation, attempts have been made to beneficially modify nickel ferrite nanoparticles by substituting various transition metal ions in to its lattice for catalytic applications. Synthesis of various modified nickel ferrite (NiM0.2Fe1.8O4 (M=Cr, Mn, Fe, Co, Ni, Cu and Zn) nanocatalysts have been carried out employing sol-gel methodology. Catalytic activity of the synthesized nanocatalysts have been evaluated both for the reduction of nitroaromatic compounds and for the deterioration of hazardous dyes. The catalytic performance of all the synthesized compositions have been found to follow the order- Mn > Cu > Co > Fe > Cr > Ni > Zn. The observed order of catalytic efficiency has also been confirmed from the completion time and rate constant values for both the catalytic reactions.

Shape-selective synthesis of Sn(MoO4)2 nanomaterials for catalysis and supercapacitor applications.

Size and shape-selective Sn(MoO4)2 nanomaterials have been synthesized for the first time using a simple hydrothermal route by the reaction of Sn(ii) chloride salt with sodium molybdate in CTAB micellar media under stirring at 60 °C temperature for about three hours. Needle-like and flake-like Sn(MoO4)2 nanomaterials were synthesized by optimizing the CTAB to metal salt molar ratio and by controlling other reaction parameters. The eventual diameter and length of the nanoneedles are ∼100 ± 10 nm and ∼850 ± 100 nm respectively. The average diameter of the flakes is ∼250 ± 50 nm. The synthesized Sn(MoO4)2 nanomaterials can be used in two potential applications, namely, catalytic reduction of nitroarenes and as an anodic material in electrochemical supercapacitors. From the catalysis study, it was observed that the Sn(MoO4)2 nanomaterials could act as a potential catalyst for the successful photochemical reduction of nitroarenes into their respective aminoarenes within a short reaction time. From the supercapacitor study, it was observed that the Sn(MoO4)2 nanomaterials of different shapes show different specific capacitance (Cs) values and the highest Cs value was observed for Sn(MoO4)2 nanomaterials having a flake-like morphology. The highest Cs value observed was 109 F g(-1) at a scan rate of 5 mV s(-1) for the flake-like Sn(MoO4)2 nanomaterials. The capacitor shows an excellent long cycle life along with 70% retention of the Cs value, even after 4000 consecutive cycles at a current density of 8 mA cm(-2). Other than the applications in catalysis and supercapacitors, the synthesized nanomaterials can find further applications in photoluminescence, sensor and other energy-related devices.

The structural and catalytic properties of nanoparticles@MOF composites: A case study of Au@ZIF-8 hybrid crystals

Strain analysis of the MOF and its composites using high-resolution X-ray diffractionmeter (XRD) was carried out and the presence of non-uniform, depth-related strain in the MOF crystals was confirmed. Further analysis showed that the magnitude and distribution of strain in MOF crystals can be tuned with the incorporation of nanoparticles (NPs). Moreover, the spatial controlled structures can also optimize functionalities of the NPs@MOF, which was exemplified by their applications on the catalytic reduction of nitroarenes. It is anticipated that the investigation of MOF structure evolution through controlling the architectures of the MOF/NPs hybrid materials will shed a light on the study of optimizing the mechanical and chemical properties of MOF composites.

Main‐Chain Organometallic Microporous Polymers Bearing Triphenylene–Tris(N‐Heterocyclic Carbene)–Gold Species: Catalytic Properties

Two triphenylene-based tris(N-heterocyclic carbene)-gold-acetylide main-chain organometallic microporous polymers (MOMPs) were obtained and fully characterized. Both materials show spherical shapes, and their size is highly dependent on the type of acetylene used in the synthetic protocol. The new solids were tested in the catalytic reduction of nitroarenes with NaBH4 and in the three-component Strecker reaction for the synthesis of α-aminonitriles, and showed high activity in both processes. Whereas the activity of the solids in the reduction of nitroarenes may be attributed to the formation of Au nanoparticles due to the use of NaBH4 as reducing agent, the activity in the Strecker reaction may originate from the Lewis acidic activation of the ketone or imine on coordination to Au.