Aldol Condensation Of Benzaldehyde Research Articles

Effect of microwave method on jasminaldehyde synthesis using solvent-free over Mg–Al–NO3 hydrotalcite catalyst

Jasminaldehyde is a widely used starting material in the chemical industry. One method for synthesizing jasminaldehyde is through the aldol condensation of benzaldehyde with 1–heptanal, using a heterogeneous catalyst called hydrotalcite Mg–Al–NO3. The synthesized catalyst was characterized using various techniques, including XRD, FT–IR, TGA, DTA, SEM, EDX, and N2 adsorption–desorption isotherm (BET) to determine its structure, morphology, thermal stability, and properties. This catalyst was tested in the studied reaction under solvent-free conditions, using both microwave and conventional heating methods (in an oil bath) to evaluate the efficiency of each method in producing jasminaldehyde. The results showed that the use of microwave heating in this reaction is particularly advantageous. It allowed for the highest conversion (>99%) of 1–heptanal, with a good selectivity (80%) towards jasminaldehyde, after only 50 min of reaction time. In contrast, conventional heating required a longer reaction time of about 8 h to achieve similar conversion and selectivity values. Furthermore, Mg–Al–NO3 demonstrated nearly sustained activity in three consecutive reuse experiments, and the durability of this catalyst was characterized using several techniques.

Solvent-Free Synthesis of Jasminaldehyde in a Fixed-Bed Flow Reactor over Mg-Al Mixed Oxide

In spite of the rapid developments in synthesis methodologies in different fields, the traditional methods are still used for the synthesis of organic compounds, and regardless of the type of chemistry, these reactions are typically performed in standardized glassware. The high-throughput chemical synthesis of organic compounds such as fragrant molecules, with more economic benefits, is of interest to investigate and develop a process that is more economical and industrially favorable. In this research, the catalytic activity of Mg-Al catalyst derived from hydrotalcite-like precursors with the Mg/Al molar ratio of 3 was investigated for the solvent-free synthesis of jasminaldehyde via aldol condensation of benzaldehyde and heptanal. The reaction was carried out in a fixed-bed flow reactor, at 1 MPa, and at different temperatures. Both Brønsted and Lewis (O2− anions) base sites, and Lewis acid sites exist on the surface of the Mg-Al catalyst, which can improve the catalytic performance. Increasing the reaction temperature from 100 °C to 140 °C enhanced both heptanal conversion and selectivity to jasminaldehyde. After 78 h of reaction at 140 °C, the selectivity to jasminaldehyde reached 41% at the heptanal conversion 36%. Self-condensation of heptanal also resulted in the formation of 2-n-pentyl-2-n-nonenal. The presence of weak Lewis acid sites creates a positive charge on the carbonyl group of benzaldehyde, and makes it more prone to attack by the carbanion of heptanal. Heptanal, is an aliphatic aldehyde, with higher activity than benzaldehyde. Therefore, the possibility of activated heptanal reacting with other heptanal molecules is higher than its reaction with the positively charged benzaldehyde molecule, especially at a low molar ratio of benzaldehyde to heptanal.

Contribution to MoO3–SiO2 and WO3–SiO2 utilization—active catalysts in jasmine aldehyde, 2-hexyl-1,3-dioxolane and methyllaurate synthesis

Several types of mixed molybdenum and tungsten oxide—SiO2 materials were prepared using sol–gel and wet impregnation method. In all cases, four different loading of MoO3 or WO3 (1, 10, 25 and 40 wt%) were prepared. Materials were characterized using X-ray diffraction, X-ray fluorescence spectroscopy and its acidity was determined by temperature programmed desorption of pyridine. Catalytic activity of these materials was tested in three model reactions providing valuable fine chemicals—aldol condensation, acetalization and esterification. These reactions are usually catalyzed by homogenous catalysts. With increasing interest in environmental protection these catalysts are replaced by heterogeneous ones—offering easy separation from reaction mixture and a possibility of catalyst reuse. More specifically the chosen reactions were: aldol condensation of benzaldehyde with heptanal giving jasmine aldehyde (1), acetalization of heptanal by ethylene glycol giving 2-hexyl-1,3-dioxolane (2) and esterification of lauric acid by methanol giving methyllaurate (3). The prepared materials proved to be catalytically active in above mentioned reactions—in aldol condensation was the best result (78% heptanal conversion, 58% selectivity to jasmine aldehyde, 24 h) obtained using Mo 40 material prepared by impregnation. This material showed to be the best together with W 40 material prepared by sol–gel process in esterification (91 or 94% conversion, 24 h). Acetalization occurs very willingly, best results (heptanal conversion > 90% and selectivity > 90%, 5 h) was obtained using Mo and W 25 and 40 prepared by sol–gel and impregnation process.

Activity Coefficients for Liquid Organic Reactions: Towards a Better Understanding of True Kinetics with the Synthesis of Jasmin Aldehyde as Showcase.

The aldol condensation of benzaldehyde and heptanal is taken as an example of reversible liquid phase organic reactions to show that inclusion of activity coefficients reveal distinct differences in conversion and product distribution when different solvents methanol, ethanol, n-propanol, or n-butanol are used. The purpose of this work is to show a pronounced solvent effect for a given set of identical kinetic parameters, i.e., the same liquid phase kinetics can result in different conversion and yield values, depending on the choice of solvent. It was shown that subsequent parameter estimation without inclusion of the activity coefficients resulted in a pronounced deviation from the ‘true’ kinetics, up to a factor of 30. It is proposed that the usage of average activity coefficients gives already a significant improvement, resulting in acceptable parameter estimates.

On the effect of mesoporosity of FAU Y zeolites in the liquid-phase catalysis

The porosity and acidity of three commercial FAU Y zeolites (including the original HY-2.6 and dealuminated HY-15/-30 zeolites) were studied comprehensively using nitrogen (N2) physisorption, and mercury (Hg) porosimetry, ammonia temperature-programmed desorption (NH3-TPD) and pyridine Fourier transform infrared (pyridine-IR) analyses. The combined N2 physisorption and Hg porosimetry is a useful tool to evaluate the hierarchical mesoporosity in the dealuminated samples, revealing that HY-15 and HY-30 possess >50% open mesoporosity in the mesopores range of 5–10 nm. The acidity of the dealuminated Y zeolites has been reduced significantly in comparison to that of the original HY-2.6, e.g. Bronsted acidity decreased by ca. 69 folds by dealuminating HY-2.6 to HY-30. Catalytic results of Fischer esterification of methanol with carboxylic acids and aldol condensation of benzaldehyde with 1-heptanal have evidenced that the critical role of mesoporosity of the dealuminated Y zeolites in liquid-phase reactions. For example, in the esterification of lauric acid with methanol, HY-15 and HY-30 with hierarchical mesopores showed better catalytic activity (i.e. conversion of lauric acid: 7.9% and 24.5%, respectively) than HY-2.6 (4.0%). The analysis of the catalytic results along with the acidic property suggests that the acidity is less influential than the porosity of zeolite catalysts. Results from this study allow us to explain the origin of the high activity of zeolites with mesoporosity in the liquid-phase catalysis.

Aldol Condensation of Benzaldehyde and Heptanal Over Zinc Modified Mixed Mg/Al Oxides

Several types of zinc modified Mg–Al layered double hydroxides were prepared. Zinc was incorporated into catalyst structure using different methods—coprecipitation, kneading or impregnation. Characterization of all solid catalysts was performed using different techniques. Acido–basic properties of prepared materials were investigated using ammonia (or carbon dioxide) temperature programmed desorption. The activity of the prepared samples was compared with pure Mg–Al oxide with Mg:Al ratio 3:1 in aldol condensation of benzaldehyde and heptanal. The influence of temperature (80–120 °C) on the reaction course was monitored. Heptanal conversion and selectivity to two main products, i.e. 2-pentylcinnamylaldehyde (jasmine aldehyde) and 2 pentylnon-2-enal, were evaluated. Zinc modified catalysts exhibited under the same conditions 15–20% higher yields of the desired jasmine aldehyde.

The synthesis and investigation of impurities found in clandestine laboratories: Baeyer-Villiger route part II; synthesis of Phenyl-2-propanone (P2P) analogues from substituted benzaldehydes

We have previously reported phenylpropan-2-one (most commonly known as phenyl-2-propanone, P2P) and methamphetamine derived by-products formed in the Baeyer-Villiger route starting from benzaldehyde. This route is a three step synthesis to P2P; an aldol condensation of benzaldehyde and methyl ethyl ketone (MEK), a Baeyer-Villiger reaction and a subsequent ester hydrolysis. We now report on our investigations into the synthesis of P2P analogues from substituted benzaldehydes via the Baeyer-Villiger route. When strong electron donating substituents are present in the three position of a substituted benzaldehyde (e.g. 3-methoxy and 3,4-methylenedioxy), the resulting aldol reaction is very sensitive to the amount of hydrogen chloride present due to the occurrence of a competing cyclization side reaction yielding various indenes by-products. In contrast, substrates bearing electron-withdrawing substituents react poorly under the Baeyer-Villiger reaction conditions described in this paper. Several new compounds were identified, namely esters 4c, f and g, amongst the known P2P precursors and derivatives. In addition, this work identifies several new by-products in the Baeyer-Villiger route namely 6, 10, 13, 14, 15 and 21; we also report the analytical data for various analogues prepared by this method and this is of value to forensic analysts.

Zeolites with isolated-framework and oligomeric-extraframework hafnium species characterized with pair distribution function analysis.

Zeolites containing framework heteroatoms (e.g., Ti, Sn, and Hf) with open coordination sites behave as solid-state Lewis acids and exhibit remarkable catalytic properties unachievable with bulk oxides. However, direct evidence confirming the incorporation of such heteroatom species into the zeolite framework is difficult to obtain because of the limited number of analytical methods capable of discerning framework incorporation from extraframework species. In this work, the structural environments of hafnium (Hf) framework and extraframework species added post-synthetically into *BEA zeolites were analyzed using coupled pair distribution function (PDF) and diffuse reflectance (DR) UV-vis measurements. PDF analysis enabled the visualization and identification of framework and extraframework HfOx species, both of which were undetectable by traditional X-ray and neutron diffraction methods. Reactivity data from the aldol condensation of benzaldehyde and acetone confirmed that framework Hf species are responsible for catalytic activity.

Aldol condensation of benzaldehyde and heptanal: a comparative study of laboratory and industrially prepared Mg–Al mixed oxides

AbstractBACKGROUNDSeveral layered double hydroxides (with Mg:Al ratio varying from 2:1 to 4:1) were prepared by a co‐precipitation method at constant pH value. The activity of laboratory prepared samples was compared with that of industrially prepared layered double hydroxides with the same Mg/Al ratio in aldol condensation of benzaldehyde with heptanal.RESULTSCharacterization of all solid catalysts was performed using different techniques (ICP‐MS, thermogravimetry, X‐ray diffraction, DRIFT spectroscopy, nitrogen physisorption method, scanning electron microscopy). Acido‐basic properties of prepared materials were investigated using ammonia (carbon dioxide, respectively) temperature programmed desorption. Heptanal conversion and selectivity to two main products, i.e. 2‐pentylcinnamylaldehyde (jasmine aldehyde) and 2‐pentylnon‐2‐enal, were monitored. All catalysts resulted in heptanal conversions higher than 95%.CONCLUSIONThe highest selectivity to jasmine aldehyde (66% at 70% heptanal conversion, 46% theoretical yield) was obtained using ESM 3:1 catalyst (100°C, heptanal:benzaldehyde = 1:2 molar, solvent‐free synthesis). © 2017 Society of Chemical Industry

Crystal growth study of K-F nanozeolite and its catalytic behavior in Aldol condensation of benzaldehyde and heptanal enhanced by microwave heating

An investigation of nanosized potassium aluminosilicate F-type zeolite (K-F, structure code EDI) converted from rice husk ash (RHA) is reported. The crystallization process was studied in an organic template-free system under microwave radiation at 100 °C and the evolution was followed by spectroscopy and microscopy techniques. The study indicated that the crystallization rate of K-F zeolite was significantly enhanced using microwave radiation. The zeolite started to nucleate at 0.5 min and flattened cuboid shaped K-F zeolite crystals (ca. 39 nm, Si/Al = 1.26) were formed after 2 min onwards. The nanocrystalline K-F zeolite exhibited good catalytic performance in solvent-free Aldol condensation reaction between benzaldehyde and heptanal, with ca. 75% reactant conversion and ca. 67% jasminaldehyde selectivity even after fifth cycle of reaction.

Potassium modified alumina as a catalyst for the aldol condensation of benzaldehyde with linear C3–C8 aldehydes

Different types of catalysts based on potassium modified alumina were prepared. The source of potassium was either potassium carbonate or potassium hydroxide. The prepared materials were characterized by UV–Vis spectroscopy, X-ray diffraction, thermogravimetry, nitrogen physisorption and tested as catalysts in the aldol condensation of benzaldehyde with C3–C8 linear aldehydes. Some of the products may serve as important fragrant compounds—especially jasmine aldehyde (prepared from heptanal) or 2-hexylcinnamylaldehyde (from octanal). It was found that the reaction rate increased with the increasing amount of potassium loaded on the catalyst. The reaction rate increased with decreasing the length of the aldehyde chain. The selectivity to the autocondensation product increased when the pore diameter of catalyst was decreased. The aldol condensation of benzaldehyde with propanal performed using alumina modified by 3.6 mmol potassium/g of material resulted in 97% propanal conversion with 89% selectivity to 2-methylcinnamylaldehyde and 6% selectivity to 2-methylpent-2-enal. The aldol condensation of benzaldehyde with octanal performed using alumina modified by 1.5 mmol potassium/g of material resulted in 29% propanal conversion with 17% selectivity to 2-hexylcinnamylaldehyde and 82% selectivity to 2-hexyldec-2-enal.

Aldol condensation of benzaldehyde with heptanal using solid-supported caesium and potassium catalysts

In this work, the possibility of using different heterogeneous basic catalysts in the aldol condensation of benzaldehyde and heptanal was tested. The solid basic catalysts were magnesium and calcium oxide, and different zeolites (HY, NaY, USY). Other catalysts were prepared – caesium-modified zeolites and MCM-41 and potassium-modified alumina. The basic properties of the used catalysts were studied using acid–base titration and temperature programmed desorption of carbon dioxide. Several techniques (UV-Vis and infrared spectroscopy, X-ray diffraction, nitrogen physisorption) were used to characterise the catalysts. These catalysts were used in the aldol condensation of benzaldehyde and heptanal, to test the influence of catalyst type, solvent, ratio of reactants and temperature on the course of reaction. Caesium and potassium leaching from catalysts was also monitored using atomic absorption spectroscopy. The best results were obtained using magnesium oxide (96% heptanal conversion, 68% selectivity to jasmine aldehyde), but all caesium- or potassium-modified catalysts showed reasonable results as well (caesium-MCM-41 40% heptanal conversion, 31% selectivity to jasmine aldehyde; potassium-alumina 62% heptanal conversion, 34% selectivity to jasmine aldehyde).

The synthesis and investigation of impurities found in Clandestine Laboratories: Baeyer–Villiger Route Part I; Synthesis of P2P from benzaldehyde and methyl ethyl ketone

The synthesis of impurities detected in clandestinely manufactured Amphetamine Type Stimulants (ATS) has emerged as more desirable than simple “fingerprint” profiling. We have been investigating the impurities formed when phenyl-2-propanone (P2P) 5, a key ATS precursor, is synthesised in three steps; an aldol condensation of benzaldehyde and methyl ethyl ketone (MEK); a Baeyer–Villiger reaction; and ester hydrolysis. We have identified and selectively synthesised several impurities that may be used as route specific markers for this series of synthetic steps. Specifically these impurities are 3-methyl-4-phenyl-3-buten-2-one 3, 2-methyl-1,5-diphenylpenta-1,4-diene-3-one 9, 2-(methylamino)-3-methyl-4-phenyl-3-butene 16, 2-(Methylamino)-3-methyl-4-phenylbutane 17, and 1-(methylamino)-2-methyl-1,5-diphenylpenta-4-ene-3-one 22.

Synthesis and Antimalarial Activity of 2-Phenyl-1,10-Phenanthroline Derivative Compounds

To develop new potential antimalarial drugs of 2-phenyl-1,10-phenanthroline 5 derivatives from 8-aminoquinoline as startingmaterial were synthesized in good yields. The synthesis of 2-phenyl-1,10-phenanthroline 5 derivatives compoundswith 8-aminoquinoline 4 as starting material through three steps has been carried out. The first step of reactions is aldolcondensation of benzaldehyde 1 with acetaldehyde 2. The result of reactions is cinnamaldehyde 3 (92.14%) in the form ofyellow solid. The second step of reactions was synthesized of 2-phenyl-1,10-phenanthroline 5 (brown solid, 54.63%)through cyclization of 8-aminoquinoline 4 with cinnamaldehyde 3 compound. The third step of reactions is methylation andethylation of 2-phenyl-1,10-phenanthroline using dimethyl sulphate (DMS) and diethyl sulphate (DES) reagents that it wasrefluxed for 17 and 19 h, respectively. The results of reactions are (1)-N-methyl-9-phenyl-1,10-phenanthrolinium sulphate 6and (1)-N-ethyl-9-phenyl-1,10-phenanthrolinium sulphate 7 in yield from 90.62% and 89.70%, respectively. The results oftesting in vitro antiplasmodial activity at chloroquine-resistant Plasmodium falciparum FCR3 strain to 2-phenyl-1,10-phenanthroline 5 derivatives obtained that (1)-N-ethyl-9-phenyl-1,10-phenanthrolinium sulphate 7 compound has higherantimalarial activity (IC 50 :0.13 ± 0.02 μM) than antimalarial activity of (1)-N-methyl-9-phenyl-1,10-phenanthrolinium sulphate6 compound (IC 50 :0.25 ± 0.01 μM) and 2-phenyl-1,10-phenanthroline 5 compound (IC 50 :2.45 ± 0.09 μM). While, the resultsof testing in vitro antiplasmodial activity at chloroquine-resistant Plasmodium falciparum D10 strain to 2-phenyl-1,10-phenanthroline 5 derivatives obtained that (1)-N-methyl-9-phenyl-1,10-phenanthrolinium sulphate 6 compound has higherantimalarial activity (IC 50 :0.10± 0.04 μM) than antimalarial activity of (1)-N-ethyl-9-phenyl-1,10-phenanthrolinium sulphate7 (IC 50 :0.18 ± 0.01 μM) and 2-phenyl-1,10-phenanthroline 5 compound (IC 50 :0.55 ± 0.07 μM).

산, 염기 이원기능 금속-유기 구조체 촉매를 이용한 알돌 축합반응

Various types of MOFs (metal-organic frameworks) were prepared via hydrothermal and post-grafting methods and applied as catalysts for the synthesis of jasminaldehyde, one of the representative perfume intermediates, by Aldol condensation of benzaldehyde with heptanal. Although both acid and base sites could catalyze the reaction, the catalytic performance was strongly dependent on the physical properties as well as the nature of functionalization on MOFs. While the use of sulfonated MOF catalysts led to decrease of jasminaldehyde selectivity regardless of MOFs used, the selectivity change was found to rely on the MOF types in the case of the amine-functionalization. Among the catalysts tested, MIL-101 shows the best catalytic per- formance, which may suggest that MIL-101 has suitable acid properties to promote the Aldol condensation and the large pore of MIL-101 is also advantageous to alleviate the diffusion problem of bulky products.

A study on factors influencing cross and self product selectivity in aldol condensation over propylsulfonic acid functionalized silica

Propylsulfonic acid functionalized silica (SFS) catalysts with varying amounts of surface propylsulfonic acid species (PrSA) and acidity were synthesized and characterized. The aldol condensation of benzaldehyde and n-heptanal over SFS catalysts was studied as a model reaction (which involves cross and self condensation reactions) to investigate the role of surface PrSA species in the cross condensation. The reaction temperature, reactant molar ratio and solvent nature (polar/non-polar) were found to be major reaction parameters controlling the cross and self aldol product selectivity. It was observed that the characteristics of carbonyl substrates influence their reactivity towards cross and self condensation over SFS catalyst.

Synthesis and structural properties of hierarchically structured aluminosilicates with zeolite Y (FAU) frameworks

Hierarchical zeolites have emerged as an important class of materials for applications in adsorption, separation and catalysis. Herein, hierarchical zeolite Y was hydrothermally synthesized using an organosilane surfactant, which was added into the conventional synthesis composition for crystalline microporous aluminosilicates as mesopore-generating agent. X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) (with KBr and pyridine), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), 27Al magic-angle spinning nuclear magnetic resonance (27Al MAS NMR) and N2 adsorption–desorption isotherms were used to characterize structural and textural features of the hierarchical zeolite Y. In addition, the molecular properties of the organosilane surfactant were investigated by density functional theory calculation. The hierarchical zeolite Y with mesoporous characteristics and the microporous crystalline structure of zeolites exhibited high catalytic activity and resistance to deactivation in the aldol condensation of benzaldehyde with n-butyl alcohol, as compared with conventional zeolite Y. This phenomenon could be attributed to improved mass transport ability of guest species through the interconnected micropore-to-mesopore networks. Such a hierarchical zeolite Y, that combines the advantages of two different pore structures, may find potential applications as advanced materials in various fields such as adsorption, separation and catalysis.

Two-Step Preparation of Benzylacetone

Two-step preparation of benzylacetone has been investigated using layered double hydroxides (LDHs) as catalysts for aldol condensation of benzaldehyde and acetone and Ni supported catalysts for consecutive hydrogenation of benzylideneacetone. Activity and selectivity of LDHs of various Mg/Al ratios to desired product, benzylideneacetone, have been compared in the liquid phase at 333 K. An aldol condensation yield at 100 % conversion of benzaldehyde was 78 % using catalyst HT-2.0. In the following, optimal hydrogenation conditions—temperature of 353 K, hydrogen pressure of 5 MPa and 5 wt% of catalyst NiSAT® 320 were found. At 95 % conversion of benzylideneacetone the selectivity to desired product was 99 %.

Direct anti and regio-specific aldol reactions of cyclododecanone catalyzed by alkali metal hydroxides: implications for supramolecular helical design

The direct aldol condensation of benzaldehyde to cyclododecanone (CDD), catalyzed by NaOH is expected to yield bis-benzylidene cyclododecanone, but we interestingly ended up with novel β-hydroxy carbonyl compounds and monobenzylidene cyclododecanone derivatives in the cases of 2-halo substituted benzaldehydes. This exceptional behaviour is due to the capability of the CDD ring to exist in the zwitter ionic form. The formation of monobenzylidine derivatives can be due to less stable hydrogen bonds between –OH and –CO groups, electrostatic interaction between aldehyde substituents and metal enolates and the bulkiness of the benzaldehyde ring substituents. We extensively optimized the reaction conditions using different solvents and alkali metal hydroxide catalysts and we are getting high yield, regio-specificity and high diastereoselectivity (anti-aldol) in β-hydroxy carbonyl compounds. The representative crystal structures were examined and they suggest the tendency of anti-aldol compounds to form supramolecular helical motifs. The β-hydroxyl carbonyl derivatives form supramolecular helices via O–H⋯O hydrogen bonds with two anti-aldol units per turn and a pitch of ∼6 A. The cyclododecanone ring adopts the minimum energy [3333] square conformation. The nucleophile will attack only from the less hindered side of the carbonyl group in the CDD ring.

Aldol condensation of benzaldehyde with heptanal to jasminaldehyde over novel Mg–Al mixed oxide on hexagonal mesoporous silica

A novel calcined hydrotalcite supported on hexagonal mesoporous silica (CHT/HMS) was synthesized and characterized by XRD, TG–DTA, pore size analysis, SEM–EDAX, and TEM. It possesses high thermal stability, high adsorption capacity and large surface area. 20% (w/w) CHT/HMS was highly active and selective in aldol-condensation of benzaldehyde with heptanal. A kinetic model was developed and validated against experimental data. Jasminaldehyde selectivity of 86% was obtained with heptanal to benzaldehyde mole ratio of 1:5 at 150 °C by using 20% (w/w) CHT/HMS. The results are explained on the basis of the bi-functional character of CHT/HMS, where the role of the weak acid sites is the activation of benzaldehyde by protonation of the carbonyl group which favors the attack of the enolate heptanal intermediate generated on basic sites. The catalyst is stable and reusable.