Aldol Condensation of Acetylferrocene under Ultrasound

Aldol condensation of acetylferrocene with aromatic aldehydes afforded ferroceny- lenones in 76%-92% yields under ultrasound at room temperature.

THE SOLID STATE ALDOL CONDENSATION REACTION OF ACETYLFERROCENE AND AROMATIC ALDEHYDES

The aldol condensation reactions of acetylferrocene with several aromatic aldehydes have been studied in the solid state.The results showed that they revealed different reactivities in the solid slate from that in solution and eight compounds have been prepared. Their structures have been characterized by UV,IR,1~HNMR,HS and elemental analysis.

Study on Aldol Condensation of HCHO and CH_3CHO over MgO Catalysts Modified by Lanthanum and Cerium

Aldol condensation of HCHO and CH_3CHO over MgO, modified MgO and Al_2O_3 with rare earth oxides, was studied. The measurement of adsorption of pyrrole on catalysts by in-situ FT-IR and NH_3 TPD indicated that the addition of elements La or Ce into MgO increased the acidity of the solid. In-situ FT-IR showed that the activation of-C=O in HCHO adsorbed on CeO-MgO and La_2O_3-MgO occurred. The measurement of catalytic activity implied that the modified catalysts can promote the formation of pentaerythritol, dipentaerthritol and tripentaerythritol.

Functioned Calix[4]arenes as Artificial Enzymes Catalyze Aldol Condensation

Aldolase models derived from calix[4]arene were designed and synthesized. The aldol condensation of p-nitrobenzaldehyde with acetone was catalyzed by the synthetic enzymes proceeded under mild conditions to offer chiefly aldol-type product in good yield.

InCl_3·4H_2O Catalyzed Aldol Condensation of Cycloalkanones with Aromatic Aldehydes

InCl34H2O catalyzes the cross-aldol condensation of cycloalkanones with aromatic aldehydes in sealed tube under solvent free condition to afford an efficient method for the synthesis of a, a-bis(substituted)benzylidenecycloalkanones.

Cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3)in Al_(2)O_(3)-AlPO_(4)for aldol condensation of methyl acetate with formaldehyde to methyl acrylate

The bare amorphous Al_(2)O_(3)-AlPO_(4)and Cs/Al_(2)O_(3)-AlPO_(4)catalysts were developed for the aldol condensation of methyl acetate with formaldehyde to methyl acrylate.The structure and property of catalyst were characterized by XRD,XPS,BET,Pyridine-IR,FT-IR,^(27)Al-MASNMR,NH_(3)-/CO_(2)-TPD and SEM.The correlation between structural features and acid-base properties was established,and the loading effect of the cesium species was investigated.Due to cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3),the weak-Ⅱacid and medium acid site densities and the product selectivity were improved.While the basic site densities of these catalysts were almost in proportion to the conversion of methyl acetate.The loaded Cs could form new basic sites and change the distribution of acid sites which further enhance the catalytic performance.As a result,the 10Cs/8AlP was proved to be an optimal catalyst with the yield and selectivity of 21.2%and 85%for methyl acrylate respectively.During the reaction,a deactivation behavior was observed on 10Cs/8AlP catalyst due to the carbon deposition,however,it could be regenerated by thermal treatment in the air atmosphere at 400℃.

FUNCTIONALIZED CYCLODEXSTRINS BEARING AM INOALKYLIMINO GROUPS AS ACTIVE CENTERS TO CATALYZE ALDOL CONDENSATIONS

Efficient catalysis of functinnatized β-cyctodextrins bearing aninoatkytimino groups for atdot condensations of nitrobenzatdehydes and acetone has been effected and substantiated by preparative experiments

Intramolecular Aldol Condensation ofα- Oxo Ketene Dibenzylthioacetals: A Facile Route to Substituted Thiophenes

A new method for the synthesis of substituted thiophenes was through intramolecular aldol condensation ofα-oxo ketene dibenzylthioacetals.All products were confirmed with IR, 1 H NMR and elemental analysis.

α,β-Dehydroamino Acid Synthesis through Proline-Catalyzed Aldol Condensation with a Glycine Schiff Base

A general protocol for the synthesis ofα,β-dehydroamino acids and their peptides was developed.Proline efficiently catalyzed an aldol condensation reaction of a glycine Schiff base with a variety of aldehydes.The hydroxy group on the benzophenone imine was crucial for high Z/E selectivity and further transimination for protecting group-freeα,β-dehydroamino esters.Peptide elongation of both the C-and N-terminals highlighted the usefulness of our present protocol.

Effect of hydration on the surface basicity and catalytic activity of Mg-rare earth mixed oxides for aldol condensation

Magnesium and rare earth mixed oxides（Mg3 REOx（RE=La, Y. Ce）） were prepared and characterized by Xray diffraction（XRD）, N_2 adsorption-desorption, infrared spectra and microcalorimetry of CO_2. The results reveal that the Mg_3 CeO_x catalyst is present in the form of Mg-Ce-O solid solution,while the Mg3 LaOx and Mg_3 YO_x catalysts are probably rare earth oxides dispersed on MgO surface. As a result, among the calcined Mg_3 REO_x catalysts, the Mg_3 CeO_x catalyst presents the highest rate constant for acetone aldolization, which is well correlated to its more homogeneous distribution of basic sites. In contrary, the Mg_3 YO_x catalyst exhibit the lowest catalytic activity for acetone aldolization. Upon hydration pre-treatment, the basic properties on the surface of the Mg_3 REO_x catalysts were changed markedly. The Mg_3 YO_x catalyst after hydration treatment shows the highest amount of basic sites on catalyst surface, and then exhibits the highest activity among the hydrated Mg_3 REO_x catalysts. These results make it possible to fine-tune basic sites for acetone aldolization.

Synthesis of straight-chain C_(49)H_(100) alkane using a modular splicing strategy

Ultra-long n-alkanes are highly valuable in both scientific research and as major constituents of specialty high-melting-point waxes.Unlike conventional methods(e.g.,Fischer–Tropsch(FT),ethylene oligomerization,and polyethylene cracking)typically resulting in wide n-alkane distributions,the elaborate design strategy presented herein allows the direct synthesis of pure,long n-alkanes using a modular splicing method with acetone,furfural,and fatty acid anhydrides or acyl chlorides as bio-blocks.The herein approach is based on a simple four-step catalytic reaction scheme involving C–C chain elongation and C–O bond activation.The synthesized pure n-alkanes had a carbon chain length as high as C_(49)(total yield of 49%).The synthesis approach also allows to selectively prepare n-alkanes with even and odd carbon numbers ranging from C15 to C_(49).This process represents a great breakthrough in the synthesis of long-chain pure n-alkanes,surpassing the carbon number limitations reported in previous methodologies.

Efficient Synthesis of Dicycloalkenopyridines:One-pot Multicomponent Condensation of Aldehydes with Cyclic Ketones

Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free a,a＇-methylene positions such as cyclopentanone or cyclohexanone in the presence of ammonium acetate and acetic acid afforded dicycloalkenopyridines with two a-arylidene groups in high yields. Under the similar reaction condition, the reaction of aromatic aldehydes with 1-tetralone having only one a-methylene position alternatively resulted in 10-aryl-2,3：5,6-dibenzoacridines.

Synthesis of high density and low freezing point jet fuels range cycloalkanes with cyclopentanone and lignin-derived vanillins

In this work,a“cyclopentanone-vanillin”strategy was proposed for the preparation of jet fuel range cycloalkanes from lignocellulose-derived ketones and lignin-derived aldehydes via aldol condensation and hydrodeoxygenation(HDO).Ethanolamine lactate ionic liquid(LAIL)exhibited excellent catalytic activity in the aldol condensation of cyclopentanone and vanillin.Desired mono-condensation and bicondensation products were obtained with yield of 95.2%at 100℃.It is found that the synergy effects between amino group of ethanolamine and hydroxyl group of lactic acid play a key role in the aldol condensation.The condensation products were converted into cycloalkanes by HDO over 5%Pd/Nb_(2)O_(5)catalyst.The density of the obtained HDO products is 0.89 g/cm^(3)and the freezing point is lower than-60℃.These results suggest that the resulted cycloalkanes can be used as additives to improve the density and low-temperature fluidity of the jet fuels.

Catalytic hydrotreatment of humins into cyclic hydrocarbons over solid acid supported metal catalysts in cyclohexane

Humins are common undesirable sideproducts during many acid-catalyzed reactions in renewable biomass platform conversion. However, few studies have been reported to the efficient utilization of humins.For the first time, the selective catalytic conversion of biomass-derived humins into cyclic hydrocarbons with high conversion rate and selectivity is presented using a home-made Ru/W-P-Si-O bifunctional catalyst. The multistage polymerization structure of humins was studied through controlled experiments.Results show that the CAC bond network can be efficiently depolymerized at a mild reaction temperature of 340–380 °C, catalyzed by the cooperative catalysis of nano-Ru particles and porous strong Lewis solid acid. Particularly, 95.4% conversion of humins was achieved under the optimal condition with up to 88.3%yield of cyclic hydrocarbons. The detailed composition after liquefaction was also analyzed. This study paves the way for the efficient production of cyclic and aromatic hydrocarbons from furan-derived humin polymer through Lewis acid-catalyzed Diels–Alder reactions between furan rings.

Formation of Pyrrolidin-1-ylcyclopentadienes via Cyclization of Alkyl 2-Dimethoxyacetyl-and 2-Ethoxalyl-4-oxopentanoates

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Total Synthesis of (±)Chrysotricine

(±)Chrysotricine 1 was synthesized by a facile route. The key steps in the synthesis were aldol condensation of dilithium salt of harman 4 with 6 -methyl-5-hepten-2-one 5 and cyclization of compound 6 using MCPBA. The 1HNMR specmim of synthetic product was identical to that of the natural sample.

Mechanistic Insights into the Catalytic Condensation of Methyl Ketones on MgO Surfaces

Ketone coupling via aldol condensation is one of the promising routes to produce cyclic and value-added precursors for renewable hydrocarbon biofuels.A first-principles-based microkinetic modeling is performed to evaluate the surface-mediated reaction mechanisms and the role of water molecules in the observed activities for 2-pentanone and 3-pentanone aldol condensation on dehydroxylated MgO(111)surface and hydroxylated terminated surface[OH-MgO(111)].We have identified the enhancement of the surface OH group to MgO(111)surface catalytic activity by destabilizing the binding strength of reaction intermediates and reducing the energy barriers of rate-determining steps(proton transfer and dehydration steps).The 2-pentanone has one elementary step less in the complete reaction mechanism of aldol condensation and preferable energy barrier for proton transfer and dehydration steps,revealing 2-pentanone as terminal ketone is more reactive than 3-pentanone as central ketone.The water molecules dominated the OH-MgO(111)surface after further addition of water,leading to the reduction of turnover frequency of the aldol condensation dimer product as the loss of aldol condensation reaction intermediates in competitive adsorption with water molecules.

One-Pot Room-Temperature Synthesis of Mg Containing MCM-41 Mesoporous Silica for Aldol Reactions

One-pot synthesis of Mg containing MCM-41(Mg-MCM-41) materials was respectively carried out by a room temperature(RT) method and a hydrothermal(HT) method for aldol condensation of 4-nitrobenzaldehyde and acetone and self-condensation of acetone. The RT method can prepare MCM-41 materials containing large amounts of Mg while maintaining the structural characteristics of MCM-41 even at very low Si/Mg ratios(large Mg loadings), but the HT method cannot. The RT method can also give more active catalysts than the HT method, because the catalysts prepared by the RT method are more basic than those prepared by the HT one. The characterization indicates that Mg atoms in the Mg-MCM-41 prepared by the RT method exist as MgO disperses well on the wall surface of pores, while those in Mg-MCM-41 prepared by the HT method are included in the bulk with a smectite-like structure.

Synthesis of 2-Benzylthio-5-phenyl-3,4-disubstituted Thiophenes by Intramolecular Condensation of α-Oxo Ketene Dibenzyl^thioacetals

A facile route to 2-benzylthio-5-phenyl-3,4-disubstituted thiophenes was described. Catalyzed by sodium hydroxide, the title compounds were synthesized in moderate to good yields simply from the intramolecular aldol type condensation of α-oxo ketene dibenzylthioacetals. The chemical selectivity for this annulation reaction was studied and discussed.

The First Total Synthesis of the （±）-Palstatin

The first total synthesis of （±）-palstatin was achieved from commercially available 5-bromovanallin and 2,4,6-trihydroxyacetophenone. SeO2 promoted oxidative cyclization reaction and Ag20 catalyzed oxidative coupling reaction served as the key steps in the synthesis successfully.