Reduction Of Benzaldehyde Research Articles

Harnessing palladium-decorated g-C3N4 nanosheets for selective catalytic benzyl alcohol synthesis

The selective reduction of benzaldehyde to benzyl alcohol (a pivotal model reaction for the low-temperature stabilization of bio-oil) was meticulously investigated. This study delved into the catalytic prowess of Pd-modified g-C3N4 nanosheets (PdxCN) within a liquid-phase environment, utilizing H2 as the reducing agent under benign conditions. A series of photocatalysts were synthesized by impregnating graphitic carbon nitride nanosheets (NS-CN) with varying weight percent loadings of Pd nanoparticles. In the context of this selective hydrogenation, the catalytic activity of Pd2CN catalysts outshone that of pure NS-CN and other reference catalysts, exhibiting remarkable efficacy with benzyl alcohol yields nearing perfection at approximately 99%. Moreover, these catalysts demonstrated enduring catalytic reusability and reproducibility. The optimization of experimental parameters, encompassing weight percent loading of co-catalyst, catalyst quantity, temperature, and reaction duration, was systematically undertaken to achieve optimal benzyl alcohol yield.

Unraveling the Crystal Structure of Sodium Tetrabenzylborate: Synthesis through the Sodium Borohydride Reduction of Benzaldehyde in the Solid State

Unraveling the Crystal Structure of Sodium Tetrabenzylborate: Synthesis through the Sodium Borohydride Reduction of Benzaldehyde in the Solid State

Alkynylation of Aldehydes Initiated by Cathodic Reduction

AbstractAlkynylation of aldehydes initiated by cathodic reduction was performed. The cathodic alkynylation required only a semi‐catalytic amount of electricity to consume the starting material completely. Cyclic voltammetry and some control experiments suggest that the electron‐generated base derived from the cathodic reduction of benzaldehyde promotes alkynylation.

Dual-core drive hydrogen transfer heterogeneous catalysts based on iridium-enzyme co-modified carbon nanotubes for aromatic aldehyde hydrogenation

Here, a novel dual-core drive transfer hydrogen heterogeneous catalysts Ir@CNT@ADH were developed by sequentially immobilizing the NADH-dependent alcohol dehydrogenase ADH and high active NADH-regenerated catalyst Pyren-Ir1 on the surface of carbon nanotubes. Two pyrene-functionalized Ir-complex, Pyrene-Ir1 and Pyrene-Ir2, were synthesized and demonstrated exceptional coenzyme NADH generation performances, ensuring continuous in situ NADH generation in the enzyme-catalyzed process. These complexes could be easily modified onto carbon nanotube materials by mild π-π conjugated adsorption. The catalysts Ir@CNT@ADH showed significantly improved catalytic hydrogenation efficiency in the reduction of benzaldehyde to the corresponding alcohol, compared to the single Pyrene-Ir1 modified carbon nanotube catalyst Ir@CNT and homogeneous catalytic system in the presence of a catalytic amount of NAD+. The yield of benzyl alcohol increased by more than 50 % in all cases. We assume that the designed dual-core drive heterogeneous catalyst strategy could effectively address the mutual inactivation problem of enzyme and Iridium complexes by blocking the contact between enzymes with Iridium complexes and enhancing the in situ regeneration property of coenzyme NADH in the enzyme catalytic system. Furthermore, catalyst Ir@CNT@ADH also demonstrated excellent catalytic hydrogeneration performances for various substituted benzaldehyde with good recycling performance. Therefore, the proposed dual-core drive heterogeneous catalyst strategy holds great potential for the combined industrial application of chemical catalysts and bioenzymes. It is expected to contribute to the development and preparation of higher-value biochemical products.

Benzaldehyde reduction over Cu-MCM-41 catalyst: Influence of the Si/Cu ratio during hydrothermal synthesis on the structure and catalytic properties

Benzaldehyde reduction over Cu-MCM-41 catalyst: Influence of the Si/Cu ratio during hydrothermal synthesis on the structure and catalytic properties

Synthesis and characterization of gold nanohybrid and its efficiency for benzaldehyde reduction

In this work, a nanohybrid of gold modified with (9Z,9′Z,9′'Z,12Z,12′Z,12′'Z)-5-((2-hydroxyethoxy)carbonyl)benzene-1,2,3-triyl tris(octadeca-9,12-dienoate (AuNPs/ HCBTDE) was synthesized using thermochemical synthesis method. First, the gold nanoparticles were synthesized by the chemical reduction process. Then, the (9Z,9′Z,9′'Z,12Z,12′Z,12′'Z)-5-((2-hydroxyethoxy)carbonyl)benzene-1,2,3-triyl tris(octadeca-9,12-dienoate) (HCBTDE) was synthesized by wet chemical procedure. The obtained HCBTDE was coupled with the gold nanoparticles to form AuNPs/ HCBTDE. It was then comprehensively characterized using several characterization techniques including ultraviolet-visible spectrophotometer, scanning electron microscopy (SEM), and EDS. Moreover, the formation of the synthesized nanoparticles and hybrid gold nanoparticles was confirmed using FTIR, 1HNMR, and 13CNMR. The modified gold nanohybrid was also evaluated as a catalyst which was investigated for the benzaldehyde hydrogenation to benzyl alcohol.

Phosphine-Catalyzed Activation of Phenylsilane for Benzaldehyde Reduction.

Hydrosilylation reactions are commonly used for the reduction of carbonyl bonds in fine chemistry, catalyzed by transition metal complexes. The current challenge is to expand the scope of metal-free alternative catalysts, including in particular organocatalysts. This work describes the organocatalyzed hydrosilylation of benzaldehyde with a phosphine, introduced at 10 mol%, and phenylsilane at room temperature. The activation of phenylsilane was highly dependent on the physical properties of the solvent such as the polarity, and the highest conversions were obtained in acetonitrile and propylene carbonate with yields of 46 % and 97 %, respectively. The best results of the screening over 13 phosphines and phosphites were obtained with linear trialkylphoshines (PMe3 , Pn Bu3 , POct3 ), indicating the importance of their nucleophilicity, with yields of 88 %, 46 % and 56 %, respectively. With the help of heteronuclear 1 H-29 Si NMR spectroscopy, the products of the hydrosilylation (PhSiH3-n (OBn)n ) were identified, allowing a monitoring of the concentration in the different species, and thereby of their reactivity. The reaction displayed an induction period of ca. 60 min, followed by the sequential hydrosilylations presenting various reaction rates. In agreement with the formation of partial charges in the intermediate state, we propose a mechanism based on a hypervalent silicon center via the Lewis base activation of the silicon Lewis acid.

Synthesis and Application of New Salan Titanium Complexes in the Catalytic Reduction of Aldehydes.

Complexes of formula [(H2N2O2)TiCl2] and [(H2N2O2)Ti(OiPr)2] (H2N2O2H2 = HOPh’CH2NH(CH2)2NHCH2Ph’OH, where Ph’ = 2,4-(CMe2Ph)C6H2) were synthesized by the reaction of the salan ligand precursor H2N2O2H2 with TiCl4 and Ti(OiPr)4, respectively, in high yields. The dichlorido complex [(H2N2O2)TiCl2] revealed to be an efficient catalyst for the reduction of benzaldehyde in toluene. Full conversion was observed after 24 h at 55 °C in THF. The same catalyst also converted phenylacetaldehyde and hydrocinnamaldehyde into the corresponding alkanes quantitatively.

Mixed valent copper oxide nanocatalyst on Zeolite-Y for mechanochemical oxidation, reduction and C–C bond formation reaction

Copper oxide (CuO) nanocatalyst supported on zeolite-Y appeared as an excellent solid phase catalyst for promoting different oxidation, reduction, and C–C bond formation reactions. The ultrafine zeolite Y supported CuO nanocatalyst selectively produced different derivatives of benzimidazoles in absence of any acids. Selective catalytic oxidation of various benzyl alcohols to the corresponding benzaldehydes was achieved under solvent-free condition using benzimidazole as the proton abstracting source. Under similar condition reduction of benzaldehyde to benzyl alcohols and the nitro-aldol condensation reaction was achieved within a very limited period through the grinding process. CuO–Y served as a suitable catalyst for the selective formation of aldehydes, alcohols, nitro-aldols, and derivatives of benzimidazole. One of the significant advantages of this technique was the non-requirement of any toxic acids, reducing agents like NaBH4, hydrazine hydride. All the reactions occurred with high yield and selectivity in absence of any solvent. Isopropanol was used as the internal reducing agent during aldehyde reduction eliminating toxic chemicals like NaBH4. More promisingly the catalyst was able to reduce selectively one aldehydic group in presence of the other such as terephthaldehyde. Some of the salient features of the process were the control oxidation of benzyl alcohol with H2O2 under mechanochemical condition, room temperature reduction of benzaldehyde without the formation of toluene. The change in the crystallite size of zeolite-Y was believed to play a crucial role in bringing high selectivity in the catalytic oxidation and reduction process.

Synthesis of Ag monoliths for multifunctional applications

A method is presented to prepare nanocomposite of silver nitrate using Tween-80 as reducing agent in presence of MnO2 and graphene oxide (GO). The designed monoliths were characterized using fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder x-ray diffraction (PXRD) analysis, Raman spectroscopy, and Brunauer-Emmettee-Teller (BET) nitrogen adsorption techniques. The nanocomposite functions as a good for developing reliable electrode materials for pseudocapacitor. Non-enzymatic electrochemical sensor against H2O2 and catalyst for the reduction of benzaldehyde (BZ) to benzyl alcohol (BA) in presence of sodium borohydride.

First-principle investigation on catalytic hydrogenation of benzaldehyde over Pt-group metals

Understanding the hydrogenation of organic compounds in the aqueous phase has always been fundamentally important for improving carbon neutral pathways to fuels and value-added chemicals. In this study, we investigated both thermodynamic and kinetic profiles of benzaldehyde hydrogenation over the Pd(111) and Pt(111) metal surfaces using density functional theory (DFT) and ab initio molecular dynamic (AIMD) simulations. The adsorption of H2 shows the mixed preference of H adsorption sites on the Pt(111), while the fcc adsorption site is dominant for H on the Pd(111). When benzaldehyde is added to the systems, we observe a strong reduction of benzaldehyde on charged Pd (111) surface compared with that on neutral surface. In contrast, charged state of the Pt(111) surface does not change their interaction. Subsequent hydrogenation reaction of benzaldehyde over Pd(111), proceeding via Langmuir-Hinshelwood mechanism, is affected by two major factors: the presence of H2O solvent and surface charge. The presence of H2O solvent greatly reduces the activation energy of CH and OH bond formation during the hydrogenation process. Furthermore, the hydrogenation step via CH bond formation is preferred thermodynamically and kinetically over OH bond formation during thermocatalytic hydrogenation, while the opposite trend holds true during electrocatalytic hydrogenation.

One-Pot Cascade Biotransformation for Efficient Synthesis of Benzyl Alcohol and Its Analogs.

Benzyl alcohol is a naturally occurring aromatic alcohol and has been widely used in the cosmetics and flavor/fragrance industries. The whole-cell biotransformation for synthesis of benzyl alcohol directly from bio-based L-phenylalanine (L-Phe) was herein explored using an artificial enzyme cascade in Escherichia coli. Benzaldehyde was first produced from L-Phe via four heterologous enzymatic steps that comprises L-amino acid deaminase (LAAD), hydroxymandelate synthase (HmaS), (S)-mandelate dehydrogenase (SMDH) and benzoylformate decarboxylase (BFD). The subsequent reduction of benzaldehyde to benzyl alcohol was achieved by a broad substrate specificity phenylacetaldehyde reductase (PAR) from Solanum lycopersicum. We found the designed enzyme cascade could efficiently convert L-Phe into benzyl alcohol with conversion above 99%. In addition, we also examined L-tyrosine (L-Tyr) and m-fluoro-phenylalanine (m-f-Phe) as substrates, the cascade biotransformation could also efficiently produce p-hydroxybenzyl alcohol and m-fluoro-benzyl alcohol. In summary, the developed biocatalytic pathway has great potential to produce various high-valued fine chemicals.

Substitutions of Amino Acid Residues in the Substrate Binding Site of Horse Liver Alcohol Dehydrogenase Have Small Effects on the Structures but Significantly Affect Catalysis of Hydrogen Transfer.

Previous studies showed that the L57F and F93W alcohol dehydrogenases catalyze the oxidation of benzyl alcohol with some quantum mechanical hydrogen tunneling, whereas the V203A enzyme has diminished tunneling. Here, steady-state kinetics for the L57F and F93W enzymes were studied, and microscopic rate constants for the ordered bi-bi mechanism were estimated from simulations of transient kinetics for the S48T, F93A, S48T/F93A, F93W, and L57F enzymes. Catalytic efficiencies for benzyl alcohol oxidation (V1/EtKb) vary over a range of ∼100-fold for the less active enzymes up to the L57F enzyme and are mostly associated with the binding of alcohol rather than the rate constants for hydride transfer. In contrast, catalytic efficiencies for benzaldehyde reduction (V2/EtKp) are ∼500-fold higher for the L57F enzyme than for the less active enzymes and are mostly associated with the rate constants for hydride transfer. Atomic-resolution structures (1.1 Å) for the F93W and L57F enzymes complexed with NAD+ and 2,3,4,5,6-pentafluorobenzyl alcohol or 2,2,2-trifluoroethanol are almost identical to previous structures for the wild-type, S48T, and V203A enzymes. Least-squares refinement with SHELXL shows that the nicotinamide ring is slightly strained in all complexes and that the apparent donor-acceptor distances from C4N of NAD to C7 of pentafluorobenzyl alcohol range from 3.28 to 3.49 Å (±0.02 Å) and are not correlated with the rate constants for hydride transfer or hydrogen tunneling. How the substitutions affect the dynamics of reorganization during hydrogen transfer and the extent of tunneling remain to be determined.

Theoretical insight into the solvent effect on the stoichiometric reduction of carbonyl compounds by ammonia borane and N‐methyl amine borane

AbstractFor the traditional reduction of ketones and aldehydes, NH3BH3 (AB) and N‐methyl amine borane (M nAB) have been effective reducing agents. However, the reaction process is indefinite and different mechanisms have been proposed; also the solvent effect, which is closely related to the mechanism, has not been considered seriously. Here we employ density functional theory to carry out a comprehensive study on the mechanism. The calculated free energy of the concerted double hydrogen transfer process is lower than the hydroboration mechanism by 4.7 kcal/mol, which indicates that reduction of carbonyl by AB is likely due to be the concerted double hydrogen transfer in both aprotic (tetrahydrofuran) and protic (MeOH) solvents. For the reduction by M nAB, the corresponding free energies of all reactions are higher than those of AB. Meanwhile, the reduction of benzaldehyde by M nAB (n = 1, 2) also favors a concerted double hydrogen transfer rather than hydroboration.

Wet chemical epitaxial growth of a cactus-like CuFeO2/ZnO heterojunction for improved photocatalysis.

Herein, a wet chemical epitaxial growth method was employed to fabricate a cactus-like CuFeO2/ZnO heterojunction for the photocatalytic reduction of benzaldehyde to benzyl alcohol. The 1D ZnO nanorods in the heterojunction make contact with the 2D CuFeO2 nanoflakes at the atomic level, therefore providing a fast charge transfer channel along the direction parallel to the CuFeO2c-axis, leading to efficient charge separation and improved photocatalytic performance.

Stability of the ketyl radical as a descriptor in the electrochemical coupling of benzaldehyde

Electroreductive coupling is an emerging pathway for the renewable upgrading of biomass derived oxygenates. This work investigates electrochemical benzaldehyde reduction on Au, Cu, Pt and Pd using reactivity testing and in situ spectroscopy.

Trapped Intermediate of a Meerwein-Pondorf-Verley Reduction of Hydroxy Benzaldehyde to a Dialkoxide by Titanium Alkoxides.

A series of titanium alkoxides ([Ti(OR)4] (OR = OCH(CH3)2 (OPri), OC(CH3)3 (OBut), and OCH2C(CH3)3 (ONep)) were modified with a set of substituted hydroxyl-benzaldehydes [HO-BzA-Lx: x = 1, 2-hydroxybenzaldehyde (L = H), 2-hydroxy-3-methoxybenzaldehyde (OMe-3), 5-bromo-2-hydroxybenzaldehyde (Br-5), 2-hydroxy-5-nitrobenzaldehyde (NO2-5); x = 2, 3,5-di-tert-butyl-2-hydroxybenzaldehyde (But-3,5), 2-hydroxy-3,5-diiodobenzaldehyde (I-3,5)] in pyridine (py). Instead of the expected simple substitution, each of the HO-BzA-Lx modifiers were reduced to their respective diol [(py)(OR)2Ti(κ2(O,μ-O')(OC6H4-x(CH2O)-2)(L)x] (OR = OPri, x = 1, L = H (1a), OMe-3 (2a), Br-5 (3a·py), NO2-5 (4a·4py); x = 2, But-3,5 (5a), I-3,5 (6a), ONep; x = 1, L = H (1b), OMe-3 (2b), Br-5 (3b·py), NO2-5 (4b); x = 2, But-3,5 (5b), I-3,5 (6b·py)), as identified by single crystal X-ray studies. The 1H NMR spectral data were complex at room temperature but simplified at high temperatures (70 °C). Diffusion ordered spectroscopy (DOSY) NMR experiments indicated that 2a maintained the dinuclear structure in a solution independent of the temperature, whereas 2b appears to be monomeric over the same temperature range. On the basis of additional NMR studies, the mechanism of the reduction of the HO-BzA-Lx to the dioxide ligand was thought to occur by a Meerwein-Pondorf-Verley (MPV) mechanism. The structures of 1a-6b appear to be the intermediate dioxide products of the MPV reduction, which became "trapped" by the Lewis basic solvate.

Rational design of thermoresponsive functionalized MCM-41 and their decoration with bimetallic Ag–Pd nanoparticles for catalytic application

Abstract MCM-41 was functionalized with thermoresponsive poly (N-isopropyl acrylamide) (p-NIPAM) by free radical polymerization. The surface of the p-NIPAM-coated on MCM-41 (MCM-41/p-NIPAM) nanocatalyst was decorated with bimetallic Ag–Pd nanoparticles for catalytic applications. The nanocatalyst was characterized by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, nitrogen adsorption/desorption analysis, thermograviametric analysis (TGA), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM) with energy dispersive X-ray (EDX) spectroscopy, x-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS). The thermoresponsive behavior of the synthesized nanocatalyst was analyzed by UV–vis spectroscopy (UV–vis) and DLS analysis. The distribution of bimetallic nanoparticles and their compositions on the polymer-coated mesoporous silica surface were investigated by EDX mapping analysis. The specific surface area was characterized by nitrogen adsorption/desorption analysis. The nanocatalyst was tested for the catalytic reduction of benzaldehyde by UV–vis analysis. Interestingly, the bimetallic nanoparticle-supported MCM-41/p-NIPAM nanocatalyst showed higher activity compared to the other counterparts. In addition, the nanocatalyst showed thermoresponsive behavior at different temperatures and could be recycled for consecutive five cycles with minimal loss in activity. This study is expected to open promising probability for the use of the above material for a range of catalytic applications.

Hydrogenation of Carbonyl Compounds over Pd in Aqueous Phase Under Charged Conditions: Role of Organic Molecular Structure

Electrocatalytic hydrogenation (ECH) is a promising approach for energy conversion utilizing renewable electricity to transform biogenic carbon sources to more useful feedstocks. Carbonyl groups are one of the most abundant and highly reactive functionalities of bio-derived molecules. Recent studies of benzaldehyde ECH showed a higher activity of C-supported Pd compared to other metals, i.e., Pt, Rh, Ni. In the present study we explore this catalytic chemistry further, comparing the reduction of aromatic and aliphatic carbonyl compounds on Pd/C with the aim to understand the influence of molecular structure on the reaction pathways and selectivity in ECH. The experiments were conducted over the potential range of -0.1 VRHE to -0.3 VRHE at low temperatures and atmospheric pressure. The aromatic carbonyl compounds benzaldehyde, acetophenone, and furfural showed significant reactivity toward hydrogenation, whereas the aliphatic carbonyl compounds butyraldehyde and cyclohexanone exhibited small or negligible reduction rates. Under these conditions, the reactive carbonyls all reduced to alcohols without secondary products. The Figure demonstrates the result of the cathodic potential on the reduction of carbonyls. The H2 evolution reaction (HER) was the prevalent side reaction during ECH and increased exponentially with negative potential. Benzaldehyde reduction rates were highest and increase linearly, followed by acetophenone reduction rates, which plateaued at -0.2 VRHE. Furfural reduction rates increased exponentially with cathodic potential albeit with lower values than benzaldehyde and acetophenone. Rotating disk electrode (RDE) experiments showed that the presence of organic compounds affects charge transfer processes to an extent that is a function of the molecular structure. These results indicate a competitive adsorption of organic compounds and hydrogen on Pd and highlight the dependence of hydrogenation rates, HER rates and charge transfer on the molecular structure, which determines the adsorption strength of the organic molecules. TCH rates are plotted against their OCV values in the Figure, showing lower rates than ECH. This allows to conclude that an electrochemical mechanism is dominating the reaction under cathodic bias. The data agrees well with a kinetic model, where the first hydrogen addition (through a proton coupled electron transfer) is the rate determining step. This work helps to understand the influence of molecular structure on the rates of electrocatalytic hydrogenation of organic compounds and simultaneous H2 evolution. Our studies will enable predictive models - based on common principles in catalysis - to be applied to other metals and organic compounds. Figure 1

Reduction of substituted benzaldehydes, acetophenone and 2-acetylpyridine using bean seeds as crude reductase enzymes

The reduction of substituted benzaldehydes, benzaldehyde, acetophenone and 2-acetylpyridine to the corresponding alcohols was conducted under mild reaction conditions using plant enzyme systems as biocatalysts. A screening of 28 edible plants, all of which have reductase activity, led to the selection of pinto, Flor de Mayo, ayocote, black and bayo beans because these enabled the quantitative biocatalytic reduction of benzaldehyde to benzyl alcohol. The biocatalyzed reduction of substituted benzaldehydes was dependent on the electronic and steric nature of the substituent. Pinto beans were the most active reductase source, reduced 2-Cl, 4-Cl, 4-Me and 4-OMe-benzaldehyde with a conversion between 70% and 100%. All the beans reduced 2- and 4-fluorobenzaldehyde at a conversion between 83% and 100%. The reduction of the ketones was low, but bayo and black beans yielded (R)-1-(pyridin-2-yl)ethanol in enantiopure form.