Cross-aldol Condensation Reaction Research Articles

CuWO4 Reinforced Co‐doped HAp Nanocomposite: Improved Photocatalytic Activity Towards Degradation of Eosin Y and Catalytic Activity in Crossed Aldol Condensation Reaction

AbstractPreventing the recombination of photoinduced charge carriers in different semiconductor photocatalysts is crucial but high‐performance photocatalyst is still challenging. Herein, we report the synthesis of a novel heterojunction of cobalt‐doped hydroxyapatite with CuWO4 i. e. Co‐HAp@CuWO4 nanocomposite by simple and facile ultrasonication technique. The morphological and structural features of the composite was examined using PXRD, FTIR, SEM, EDS, TEM, UV‐DRS and XPS techniques. The optical analysis showed that the band gap of Co‐HAp@CuWO4 nanocomposite is 1.59 eV which is very much lower than pure HAp. The photocatalytic efficiency of Co‐HAp@CuWO4 was assessed in the degradation of Eosin Y dye under solar light irradiation. The result of degradation capacity is 94.5 % after 70 minutes of solar irradiation and it follows pseudo first‐order kinetics. The impact of different reaction parameters such as catalyst amount, initial concentration of the dye, and solution pH was also examined. The recyclability test showed that the synthesized material was highly stable in the visible‐light driven dye degradation. Heterogeneous catalytic efficacy of the prepared nanocomposite was examined in the crossed aldol condensation reaction of benzaldehyde and acetone and the outcomes confirmed that dibenzylideneacetone (DBA) was formed in the condensation reaction in outstanding yields under optimum conditions.

Synthesis of Dibenzalacetone using Sonochemistry and Its Antibacterial Activity Against Escherichia coli

The synthesis of dibenzalacetone, a ketone compound with potential antibacterial properties, especially against <em>Escherichia coli</em>, has typically involved time-consuming methods. This study adopts sonochemistry, an increasingly popular technique recognized for its efficiency and quick yield. The aim is to synthesize dibenzalacetone using the sonochemical method and evaluate its antibacterial efficacy against <em>E. coli</em>. The synthesis process includes a cross-aldol condensation reaction between acetone and benzaldehyde, catalyzed by NaOH, conducted in an ultrasonic bath at 35 °C for 1-5 minutes. The optimal synthesis condition, achieved in 4 minutes, resulted in a 76.56% yield of dibenzalacetone, characterized as a bright yellow solid with a melting point of 111-114°C. Techniques such as FT-IR, GC-MS, 1H-NMR, and 13C-NMR spectrometry were employed for structural characterization. The FTIR analysis revealed various functional groups, including C=O ketone, C=C aromatic, and C-H aromatic. GC-MS data confirmed the molecular weight of dibenzalacetone at m/z 234.1. Furthermore, <sup>1</sup>H-NMR and <sup>13</sup>C-NMR analyses provided detailed insights into the compound's chemical shifts and structural groups, affirming the successful synthesis of dibenzalacetone. The antibacterial activity of dibenzalacetone against <em>E. coli</em> was tested at concentrations ranging from 5% to 20%. Notably, at a 15% concentration, dibenzalacetone exhibited antibacterial activity comparable to amoxicillin. These findings suggest that dibenzalacetone, efficiently synthesized via sonochemistry, not only achieves a high yield but also has potential as an antibacterial agent against <em>E. coli</em>. This research highlights the efficacy of sonochemistry for the rapid and effective synthesis of compounds with significant medical applications.

Solvent-free cross aldol condensation of aldehydes and ketones over SrMo1-xNixO3-δ perovskite nanocrystals as heterogeneous catalysts

Aldol condensation is arguably one of the most fascinating reactions that leads to the formation of C–C bonds. Its use in the pharmaceutical industry to synthesis complex drugs from simple aldehydes and ketones has become of paramount importance. Although this is one reaction that has lured a lot of attention, not enough has been explored in heterogeneous catalysis. In this work we have successfully synthesized multicationic perovskites via the soft-template method and characterized them thoroughly. The synthesized perovskite nanocrystals were found to have small SBET however their catalytic application in the conversion of benzaldehyde (BAL) in the aldol condensation with diethyl ketone (DEK) was found to be astonishing. The synthesis was confirmed using many techniques, from determining the oxidation states of the materials using XPS. This gave access to determine the coordination of the metals in the perovskite lattice and also qualitatively assess the oxygen environments that exist. The oxygen vacancies and SBET were used to assess the activity of the perovskite catalysts in the cross-aldol condensation reaction. The optimal conditions for this aldol condensation were found to be 120 °C after 25 h with no solvent using SrMo0.5Ni0.5O3-δ inorganic perovskite which had the highest amount of oxygen vacant sites which gave a conversion of 88 % and an 82 % selectivity towards the desired cross-aldol condensation product. The use of dimethylformamide (DMF) for this reaction is discouraged as it reacts with BAL to produce a higher amide.

Novel Route to Produce Hydrocarbons from Woody Biomass Using Molten Salts.

The thermochemical decomposition of woody biomass has been widely identified as a promising route to produce renewable biofuels. More recently, the use of molten salts in combination with pyrolysis has gathered increased interest. The molten salts may act as a solvent, a heat transfer medium, and possibly also a catalyst. In this study, we report experimental studies on a process to convert woody biomass to a liquid hydrocarbon product with a very low oxygen content using molten salt pyrolysis (350–450 °C and atmospheric pressure) followed by subsequent catalytic conversions of the liquids obtained by pyrolysis. Pyrolysis of woody biomass in molten salt (ZnCl2/NaCl/KCl with a molar composition of 60:20:20) resulted in a liquid yield of 46 wt % at a temperature of 450 °C and a molten salt/biomass ratio of 10:1 (mass). The liquids are highly enriched in furfural (13 wt %) and acetic acid (14 wt %). To reduce complexity and experimental issues related to the production of sufficient amounts of pyrolysis oils for further catalytic upgrading, model studies were performed to convert both compounds to hydrocarbons using a three-step catalytic approach, viz., (i) ketonization of acetic acid to acetone, (ii) cross-aldol condensation between acetone and furfural to C8–C13 products, followed by (iii) a two-stage catalytic hydrotreatment of the latter to liquid hydrocarbons. Ketonization of acetic acid to acetone was studied in a continuous setup over a ceria–zirconia-based catalyst at 250 °C. The catalyst showed no signs of deactivation over a period of 230 h while also achieving high selectivity toward acetone. Furfural was shown to have a negative effect on the catalyst performance, and as such, a separation step is required after pyrolysis to obtain an acetic-acid-enriched fraction. The cross-aldol condensation reaction between acetone and furfural was studied in a batch using a commercial Mg/Al hydrotalcite as the catalyst. Furfural was quantitatively converted with over 90% molar selectivity toward condensed products with a carbon number between C8 and C13. The two-stage hydrotreatment of the condensed product consisted of a stabilization step using a Ni-based Picula catalyst and a further deep hydrotreatment over a NiMo catalyst, in both batch setups. The final product with a residual 1.5 wt % O is rich in (cyclo)alkanes and aromatic hydrocarbons. The overall carbon yield for the four-step approach, from pinewood biomass to middle distillates, is 21%, assuming that separation of furfural and acetic acid after the pyrolysis step can be performed without losses.

Greener Synthesis of Jasminaldehyde via Cross Aldol Condensation Reaction Using Recyclable Phase Transfer Catalysis and its Cosmetic Application

Jasminaldehyde or alpha amyl cinnamic aldehyde is a commonly used aroma molecule in perfume formulationsThe aldol condensation of equimolar n-heptanal and benzaldehyde in NaOH using a surfactant catalyst cetyltrimethylammonium bromide to achieve high cross aldol product Jasminaldehyde selectivity was studied. The process is highly efficient due to the recyclability of the catalyst. The process was studied for four cycles of catalyst reusability. The selectivity of the cross product was dependent on the temperature, surfactant concentration, and mixing. The olfactive profile of Jasminaldehyde obtained with 0.1 M surfactant solution was identical to the standard. Jasminaldehyde formulation was created and applied to in-home care applications.

Dehydrogenation of ethanol over CuO–Mg–Y for cross-aldol condensation with aryl aldehydes

An economically viable approach for the synthesis of different α, β-unsaturated aldehydes through modified cross-aldol condensation reaction has been developed. In this synthetic process, acetaldehyde is generated in situ through the catalytic dehydrogenation of the ethanol. The dehydrogenation reaction is found to occur over copper oxide nanoparticles supported on magnesium exchanged zeolite-Y. The formation of acetaldehyde through dehydrogenation of ethanol is confirmed by the modified Hantzsch reaction. Different kinetic studies have been performed to predict the rate of acetaldehyde as well as cinnamaldehyde formation. The formation of α, β-unsaturated aldehydes through the dehydrogenative cross-aldol reaction of ethanol with various aldehydes are found to be dependent on different reaction parameters viz temperature, catalyst amount, time, and the nature of bases. The catalytic dehydrogenation process is found to occur within 80–100 °C. TDDFT calculations are used to correlate the electronic spectra of Hantzsch reaction product with the experimental one.

Nontraditional Aldol Condensation Performance of Highly Efficient and Reusable Cs+ Single Sites in β-Zeolite Channels.

Aldol reactions (self- and cross-aldol condensations) for conjugated enone synthesis were efficiently performed on large-sized Cs+ single sites (1 wt %) confined in β-zeolite channels in toluene, which showed the highest level of catalytic aldol condensation activity among reported zeolite catalysts. In general, aldol condensation reactions for C-C bond synthesis can proceed by acids (e.g., H+), bases (e.g., OH-), enolate species, and acidic or basic solid catalysts. However, the Cs+ single site/β sample without significant acid-base property showed unprecedented, efficient, and reusable catalysis for self-aldol and cross-aldol condensations. Intrinsically inactive Cs+ single sites due to the noble-gas electronic structure were transformed to active Cs+ single sites in β-zeolite channels. Cs+/β has many advantages such as broad substrate scope, eco-friendliness, high product selectivity and yield, and simple work-up procedure. Thus, the Cs+ single site/β provides an attractive and useful methodology for practical C-C bond synthesis. On the basis of the Cs+/β characterization by X-ray photoelectron spectroscopy (XPS), in situ X-ray absorption fine structure (XAFS) (X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS)), and temperature-programmed desorption (TPD), density functional theory (DFT) calculations of the self- and cross-aldol condensation reaction pathways involving the transition states on the Cs+ single site in β-zeolite channel revealed nontraditional concerted interligand bond rearrangement mechanisms.

Entrapped NbOx clusters in MFI zeolite for sustainable acid catalysis

Abstract Entrapping the small NbOx clusters into MFI zeolite crystals was directly prepared via a facile hydrothermal method, assisting with the sodium citrate and EDTA-2Na to dissolve and chelate the niobium precursors. The existing states and configurations of Nb species in the zeolites were carefully characterized by a series of techniques including XRD, FTIR, SEM, TEM, UV–Vis, XPS and Raman. These results clearly indicated that the entrapped oligomeric NbOx clusters in MFI zeolite crystals contained Nb-OH, Nb=O and Nb-O-Si bonds. These characters were the origin of both Lewis and Bronsted acid sites for these Nb-MFI samples, which was vividly confirmed by FTIR spectroscopy with pyridine absorption and solid-state NMR spectroscopy with ammonia and TMPO as probing molecules techniques. The as-prepared Nb-MFI zeolites were employed as sustainable Lewis acids in several catalytic reactions. Especially, Nb-MFI zeolites exhibited remarkable catalytic performance in the cross-aldol condensation between furfural and acetone for biomass upgrading, surpassing traditional Lewis acidic zeolites Sn-MFI and Sn-BEA in terms of activity and selectivity, respectively. The 2.6%Nb-MFI also showed very good stability during reaction and it could be recycled for six times without loss in activity. Finally, 2.6%Nb-MFI was verified as a general catalyst for the cross-aldol condensation reaction between small-molecule aldehydes and ketones. All these results demonstrate the great potential of Nb-MFI as a robust catalyst for the shape-selective Lewis acid catalysis. The synthesis strategy developed herein could be readily extended to the construction of zeolite entrapped high-valence transition metal clusters for catalytic applications.

Investigation of catalytic activity of solid acidic Fecl3/bentonite catalyst on the synthesis of some (E)-1-(2,4-dimethylthiazol-5-yl)-3-phenylprop-2-en-1-ones by solvent-free technique

Abstract In this work, an attempt was made to synthesized more than 90% yields of (E)-1-(2,4-dimethylthiazol-5-yl)-3-phenylprop-2-en-1-one by cross-aldol condensation reaction of 5′acetyl 2,4-dimethylthiazole with various substituted benzaldehydes in the presence solid acidic FeCl3/Bentonite catalyst using microwave irradiation under solvent-free conditions. The synthesized (E)-1-(2,4-dimethylthiazol-5-yl)-3-phenylprop-2-en-1-one derivative was characterized by physical constants, UV, FT-IR, 1H NMR and 13C NMR spectral data. In this condensation, the effect of catalytic activity was investigated by the obtained yield of enones and reusability. This greener technique offered for high yield of 2,4-dimethylthiazole enones.

Catalytic application of 3-methyl-1-sulfonic acid imidazolium tetrachloroferrate as nanostructured catalyst on the cross-aldol condensation reaction of cycloalkanones with aldehydes

Catalytic application of 3-methyl-1-sulfonic acid imidazolium tetrachloroferrate as nanostructured catalyst on the cross-aldol condensation reaction of cycloalkanones with aldehydes

Synthesis of Zingerone Using NiCl<sub>2</sub>•6H<sub>2</sub>O-NaBH<sub>4 </sub>as a Selective Hydrogenation Reaction Agent

Synthesis of zingerone (4-(4-hydroxy-3-methoxyphenyl)-2-butanone) has been done. The first step was to synthesize the compound (4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-on) through a cross aldol condensation reaction between vanilin:acetone mol ratio of 1:5:5, for 5 hours in high yields (97%). The second step was the selective hydrogenation of (4-(4-hydroxy-3-methoxyphenyl)-3-buten-2-on) with NiCl2•6H2O-NaBH4 catalyst in mild condition. Based on the FT-IR, 13C-NMR and 1H-NMR and GC-MS analyses, the synthesis of zingerone has been successfully synthesized by selective hydrogenation reaction with 80% yield.

Study of the antibacterial and antifungal activities of synthetic benzyl bromides, ketones, and corresponding chalcone derivatives.

Several applications of chalcones and their derivatives encouraged researchers to increase their synthesis as an alternative for the treatment of pathogenic bacterial and fungal infections. In the present study, chalcone derivatives were synthesized through cross aldol condensation reaction between 4-(N,N-dimethylamino)benzaldehyde and multiarm aromatic ketones. The multiarm aromatic ketones were synthesized through nucleophilic substitution reaction between 4-hydroxy acetophenone and benzyl bromides. The benzyl bromides, multiarm aromatic ketones, and corresponding chalcone derivatives were evaluated for their activities against eleven clinical pathogenic Gram-positive, Gram-negative bacteria, and three pathogenic fungi by the disk diffusion method. The minimum inhibitory concentration was determined by the microbroth dilution technique. The results of the present study demonstrated that benzyl bromide derivatives have strong antibacterial and antifungal properties as compared to synthetic chalcone derivatives and ketones. Benzyl bromides (1a and 1c) showed high ester activity against Gram-positive bacteria and fungi but moderate activity against Gram-negative bacteria. Therefore, these compounds may be considered as good antibacterial and antifungal drug discovery. However, substituted ketones (2a–b) as well as chalcone derivatives (3a–c) showed no activity against all the tested strains except for ketone (2c), which showed moderate activity against Candida albicans.

P-Toluene sulfonic acid (PTSA)-MCM-41 as a green, efficient and reusable heterogeneous catalyst for the synthesis of jasminaldehyde under solvent-free condition

This paper reports the synthesis of p-Toluene sulfonic acid (PTSA)-MCM-41 by impregnation method and its characterization XRD, FT-IR, TGA, N2 adsorption–desorption isotherms, SEM, and TEM. The impregnated catalysts were used to catalyse cross-aldol condensation of active methylene bearing aliphatic aldehydes with aromatic aldehydes under solvent and metal-free condition particularly in the synthesis perfumery chemical-jasminaldehyde and related compounds. The as synthesized catalyst PTSA-MCM-41 has displayed high efficiency (selectivity up to 91%) in catalyzing cross-aldol condensation reaction and was reusable (5 cycles) with no apparent loss in activity. The catalytic performance of PTSA-MCM-41 was compared with other catalysts viz., ZnO, proline, proline-LDH, PTSA, PTSA-zirconia and PTSA-zeolite where PTSA-MCM-41 showed better performance particularly in synthesis of jasminaldehyde.

Design, characterization, and use of N,N-diethyl-N-sulfoethanaminium hydrogen sulfate {[Et3N-SO3H]HSO4} as a novel and highly efficient catalyst for preparation of α,α′-bis(arylidene)cycloalkanones

The aim of this work is to introduce a novel and attractive protic acidic ionic liquid as catalyst for organic synthesis. To achieve this aim, N,N-diethyl-N-sulfoethanaminium hydrogen sulfate {[Et3N-SO3H]HSO4} was prepared by reaction of NEt3 with ClSO3H and then with H2SO4. The novel acidic ionic liquid was identified by Fourier-transform infrared (FT-IR), 1H nuclear magnetic resonance (NMR), 13C NMR, and mass spectroscopies. Its catalytic activity was then examined in the cross-aldol condensation reaction of arylaldehydes with cycloalkanones under solvent-free conditions, obtaining α,α′-bis(arylidene)cycloalkanones in high yield after short reaction time.

Mechanistic studies of aldol condensations in UiO-66 and UiO-66-NH2 metal organic frameworks

A full mechanistic investigation is proposed for the industrially important cross-aldol condensation reaction of heptanal with benzaldehyde on the UiO-66 and the amino-functionalized UiO-66-NH2 metal–organic frameworks to form jasminaldehyde. Several experimental studies indicate that the activity for the aldol condensation reaction can be increased by proper functionalization of the material, e.g. by introducing an additional basic amino site and thus creating a bifunctional acid–base catalyst for the aldol condensation. The precise molecular level origin for this behavior is to date unclear. Herein state-of-the-art Density-Functional Theory (DFT) calculations have been performed to unravel the mechanism of the cross- and self-aldol condensations of benzaldehyde and propanal. To this end free energy calculations have been performed on both extended cluster and periodic models. It is found that the mechanism on both catalysts is essentially the same, although a slightly stronger adsorption of the reactants and slightly lower barriers were found on the amino functionalized material, pointing toward higher initial activities. New experiments were performed to confirm these observations. It is indeed found that the initial activity toward cross-aldol condensation on the amino functionalized material is higher, although after about 40min of reaction both materials become equally active. Our results furthermore point out that the basic amino groups may promote side reactions such as imine formation, which is induced by water. The study as presented can assist to engineer materials at the molecular level toward the desired products.

Synthesis of Novel Indazole-Derived Ionic Liquids

A very simple, convenient, two-step halide-free method for the synthesis of a novel homologous series of 36 room-temperature indazolium ionic liquids is reported, in which the indazolium moiety is substituted with different n-alkyl chains, and coupled with a tetrafluoroborate anion. As an example, the newly designed indazolium ionic liquid, 1-ethyl-2-pentyl-2H-indazol-2-ium tetrafluoroborate ([EPentIn]BF4) is employed as an ionic solvent to demonstrate its efficiency as a green solvent in a crossed aldol condensation reaction.

An efficient solid base catalyst from coal combustion fly ash for green synthesis of dibenzylideneacetone

The objective of the investigation was to evaluate the catalytic efficiency of a solid base catalyst (SBC) derived from coal combustion fly ash to synthesize dibenzylideneacetone (DBA, 94% yield). The catalyst was produced using potassium hydroxide (30wt.%) on thermally activated F-type fly ash. The physico-chemical, mineralogical and morphological characterization of the fly ash and catalyst were performed using XRF, FT-IR, BET surface area analyser, XRD and SEM-EDS. The results of such analysis revealed that the catalyst obtained was associated with strong basic hydroxyl (OH) sites that were highly suited to produce DBA by crossed aldol condensation reaction.

Study of in situ generation of carbocationic system from trityl chloride (Ph3CCl) which efficiently catalyzed cross-aldol condensation reaction

Abstract Organocatalyst trityl chloride (Ph3CCl), by in situ formation of trityl carbocation with inherent instability, efficiently promotes the cross-aldol condensation reaction between cycloalkanones and arylaldehydes in solvent-free and homogeneous media to afford α,α′-bis(arylidene)cycloalkanones in high yields. Moreover, an attractive and plausible mechanism based on observations and the literature is proposed for the reaction.

A green and efficient amine-functionalized ionic liquid/H2O catalytic system for the synthesis of α,α′-bis(substituted benzylidene)cyclopentanones

An environmentally benign and convenient amine-functionalized ionic liquid (IL) catalytic system was explored for the preparation of α,α′-bis(substituted benzylidene)cyclopentanones by the cross-aldol condensation of aromatic aldehydes with cyclopentanone. High yields were obtained without using any organic solvents. The condensation products can be separated easily and the ILs can be recovered and reused at least five times without apparently loss of activity. The potential mechanism of the cross-aldol condensation reaction in this IL catalytic system is discussed.

NH4H2PO4/SiO2: a recyclable, efficient heterogeneous catalyst for crossed aldol condensation reaction

Crossed aldol condensation of aromatic aldehydes with cyclic ketones in the presence of catalytic amount of NH4H2PO4/SiO2 (as a safe, green, and cheap heterogeneous catalyst) under solvent-free condition afforded α,ά-bis(substituted-benzylidene) cycloalkanones in high yields. This method is general with respect to all types of aromatic aldehydes and is an eco-friendly procedure. And the catalyst is easily prepared, stable, reusable, and efficient under the reaction conditions.