Weak Acid Catalyst Research Articles

A regiospecific fischer indole reaction with 3‐oxo‐24‐nor‐allobetulin

AbstractFirst case of regiospecific formation of indole fused with a triterpene scaffold is observed. Starting from 3‐oxo‐24‐nor‐allobetulin Fischer reaction with phenylhydrazine under the influence of weak acid catalyst led to 3H‐indole (indolenine) 4. This process was accompanied by a change in the configuration of the methyl group at C‐4 that was confirmed by x‐ray diffraction method. On the other hand, 3,2‐indole 5 was synthesized under the influence of strong acid catalyst (using phenylhydrazine hydrochloride in AcOH acid or phenylhydrazine in MeOH with a few drops of HCl).

Influence of pseudoboehmite properties on characteristics of CoMo/ASA-Al2O3 catalysts for selective hydrotreating of FCC gasoline

The influence of alumina precursor (pseudoboehmites) in CoMo/ASA + Al2O3 catalysts on catalytic activity in FCC gasoline hydrotreating has been studied. Pseudoboehmites prepared by alcoholate, precipitate and hydrothermal technologies were used. Parent powders, supports and catalysts were characterized by low-temperature N2 adsorption, TPD of ammonia, STEM, HRTEM, UV–vis spectroscopy. Catalysts were tested in hydrotreating of the model FCC gasoline feedstock. It is shown that the choice of pseudoboehmite has significant effect on textural, acid and mechanical properties of supports and catalysts, as well as dispersity of the active phase. The type of pseudoboehmite affects the amount of tetrahedral cobalt in catalysts that changes surface activity per 1 g of the catalyst. The linear dependence between the ratio of the medium and weak acid sites and catalyst selectivity was found. It is established that isomerizing activity is higher than the hydrogenating one, when medium/weak acid sites ratio in the catalyst is lower than 1.85.

Isomerization of Raw Turpentine Using Various Combination of Strong and Weak Acid Catalyst for Eucalyptol Production

There has been large interest to isomerize raw turpentine to produce a number of derivative products that has higher economic value. This process is often conducted using homogenous acid catalysts. Catalyst screening is often challenging to target a certain derivative product, such as cineole. The aim of present work is investigate various combination of strong and weak acid catalyst to obtain cineole. Strong acids used in this research were PTSA, hydrochloric acid, sulfuric acid. In addition, the weak acids were oxalic acid dihydrate, citric acid, and formic acid. Commercial turpentine was mixed with strong and weak acid with 4:1:6 ratio respectively, heated up to 85oC for 6 hours for each combination of strong and weak acid. The result from GC-MS analysis shows that combination of hydrochloric acid and formic acid gave the highest eucalyptol yield around 9.67% along with other valuable product such as camphene, limonene, and a-terpinolene.

Isomerization of Raw Turpentine for Cineole using Response Surface Methodology (RSM) : Influence of Acid Ratios and Residence Time

Turpentine is a potential non-wood product from pine tree forest in Indonesia. Turpentine has a wide application in industry mainly as solvent. Isomerization of turpentine is an attractive route to obtain a higher value fine chemical such as cineole. Acid catalyst is often used for this purpose and screening of numerous combination of acid catalysts is often challenging. Therefore, an investigation of isomerization operating condition is important. The aim of present work is to investigate the influence of several acids ratios, and residence time. The raw turpentine was obtained from PT Perhutani Anugerah Kimia (PAK) Trenggalek, East Java. Here, we have investigated the influence of raw turpentine to acid catalyst ratios as well as residence time using central composite design (CCD) of 22 factorial design. In this work, the strong acid catalysts used is hydrochloric acid (HCl) and the weak acid catalysts is formic acid (HCOOH). The result from GC-MS analyses showed that isomerization of raw turpentine using combination of HCl and formic acid can produce cineole compound along with other valuable products such as camphene and limonene. Herein, we have reported the highest yield of cineole as high as 11.5% which is in close agreement with model prediction. It is expected that this work may provide a useful path for cineole production in a larger production scale.

Synthesis of 3-Silylated 3-Sulfolenes from Propargylsilanes and their Reductive Desulfitation

Protonation of propargylsilanes induces 1,2-silyl group shift and provides 2-silylated dienes. If this reaction is performed in liquid SO2, the diene formation is followed by instant cheletropic SO2 addition, and 3-silylated 3-sulfolenes are obtained. Liquid SO2 as polar and Lewis acidic reaction medium makes it possible to use relatively weak Bronsted acid catalysts such as H2O and benzoic acid. Depending on the starting material, reductive desulfitation of 3-silylated 3-sulfolenes provides vinyl, allyl, or aliphatic silanes.

A method to control terpineol production from turpentine by acid catalysts mixing

Terpineol, a promising valorisation product of pine industry, is widely used as an active ingredient for disinfectant soap, cleansers, perfumes, and pharmaceutical purposes. Synthesis of terpineol is generally carried out by separation of α-pinene compounds from crude turpentine through fractionation and then hydrated (addition of water) with the help of acid catalysts. However, direct turpentine hydration without pre-fractionation process can be more beneficial from economic and process point of views. This study aims to investigate the effect of both single and mixed/combined catalysts towards terpineol yield. Combined strong and weak acid catalysts were required to obtain high feed conversion and terpineol yield. The selectivity of terpineol is then correlated to the solubility of a weak/organic acid. In this study, the highest yield of terpineol was 54.0 ± 8.2%-w/w using combination of formic acid and sulphuric acid.

Ultrasonic-Assisted Synthesis of Twot-Butoxycarbonylamino Cephalosporin Intermediates on SiO2

Herein, we describe a facile and high efficient strategy for the synthesis of two forms of the 7β-t-butoxycarbonylamino-3-chloromethyl-3-cephem-4-carboxylates using ultrasonic irradiation. By SiO2as weak Lewis acid catalyst, 4-methoxybenzyl 7β-t-butoxycarbonylamino-3-chloromethyl-3-cephem-carboxylate (Boc-ACLE) and benzhydryl 7β-t-butoxycarbonylamino-3-chloromethyl-3-cephem-4-carboxylate (Boc-ACLH) were successfully synthesized through the efficient protection of theN-t-butoxycarbonyl (N-Boc), and the reactions occurred at low temperature requiring short reaction times and exhibiting excellent isolated yields (96% and 96.2%, resp.). The advantages of this reaction route including the usage of economical reagents and mild reaction conditions and high isolated yield make the two significantt-butoxycarbonylamino cephalosporin intermediates possible in large-scale production.

Solvent- and Microwave-Assisted Dehydrations of Polyols to Anhydro and Dianhydro Polyols

Carbohydrate polyol (sorbitol, mannitol, and xylitol) dehydrations by both strong and weak acid catalysts were enhanced by microwave irradiation when performed in aqueous dioxane. Reaction conditions such as the percent of water, type and concentration of acid, reaction time, and temperature were varied. Reactions with different conditions were compared by using the “combined severity” parameter. An 88% yield of the dianhydropolyol isosorbide was achieved by heating sorbitol in a microwave for only 20 min at 205 °C in 7% water/dioxane with H2SO4 as the catalyst, while heating for 1.5 h at 210 °C with the weak acid salt NaHSO4 gave 74% isosorbide. An 85% yield of 1,4-anhydroxylitol was achieved by heating xylitol in a microwave, with H2SO4 as the catalyst, for 15 min at 180 °C in 28% water/dioxane. Increasing reaction severity in the presence of the H2SO4 catalyst gave organic sulfate impurities due to solvent cleavage; in contrast, no solvent cleavage was observed with the weak acid catalyst NaHSO4.

Pyridine and Pyridinium Electrochemistry on Polycrystalline Gold Electrodes and Implications for CO2 Reduction

We examine the electrochemical behavior of pyridine (py) and pyridinium ion (pyrH+) on gold electrodes in inert nitrogen (N2) and carbon dioxide (CO2) environments to evaluate potential catalytic roles of nitrogen heterocycles in electrochemical CO2 reduction. Analysis of the pyridine and pyridinium systems shows that gold electrodes exhibit unique pyrH+ and CO2 electrochemistry compared with previous work on platinum electrodes or photoelectrode systems. Specifically, analysis of the data shows specific adsorption of pyridine/pyridinium, an irreversible reduction wave at −1.0 V vs Ag/AgCl associated with the one-electron reduction of pyridinium, and an enhanced reductive current when CO2 and pyrH+ are included together in the aqueous solution. Our results show no evidence to support formation of carbon-containing reduction products and implicate CO2 as a possible weak acid catalyst for production of dihydrogen.

Synthesis of Common-sized Heterocyclic Compounds by Intramolecular Cyclization over Halide Cluster Catalysts

Abstract Five- to seven-membered common-sized heterocyclic compounds containing an oxygen, sulfur, or nitrogen were synthesized by the intramolecular condensation of α,ω-hydroxy, mercapto, or amino alkanes, respectively, over halide cluster complexes as a thermally stable molecular solid weak acid catalyst in the gas phase at temperatures ≥150 °C. From ω-mercapto and ω-amino alcohols, cyclic sulfides and amines were obtained, respectively. These unimolecular reactions are thermodynamically and kinetically favored.

Synthesis and characterization of hyperbranched aromatic poly(ether ketone)s functionalized with carboxylic acid terminal groups

A new type of hyperbranched aromatic poly(ether ketone) terminated with carboxylic acid groups (P2) was synthesized via a one-step polycondensation of a symmetric AB2 monomer, 4,4′-(m-phenylenedioxy)-bis(benzenecarboxylic acid), using phosphorous pentoxide-methanesulfonic acid (PPMA) as a condensing agent and solvent. Subsequently, the terminal carboxylic acid functional group of P2 was converted to an ethyl ester functional group by treatment with thionyl chloride followed by ethanol in the presence of triethylamine. The weight-average molecular weight (Mw) of the ethyl ester-terminated hyperbranched poly(ether ketone) (P3) was measured by gel permeation chromatography. By changing the reaction time and the amount of PPMA, Mw can be controlled in the range of 4.2 × 104 to 1.6 × 105. P2 was soluble in polar solvents, and P3 was soluble in less-polar solvents. The thermal stabilities of the poly(ether ketone)s were investigated using thermogravimetric analysis, which indicated that the decompositions of P2 and P3 start at around 150 and 200 °C, respectively. The inherent viscosities of P2 were in the range of 0.101–0.171, while those of P3 ranged from 0.067 to 0.112. The ion exchange capacities calculated by titration were in the range of 2.2–2.8 mol kg−1 according to the difference in molecular weights. P2 was tested as a weak-acid catalyst and exhibited a certain catalytic activity for the hydrolysis of cellulose to glucose. A new type of hyperbranched aromatic polyetherketone terminated with carboxylic acid group was synthesized by one-step polycondensation of a symmetric AB2 monomer, 4,4′-(m-phenylenedioxy)-bis(benzenecarboxylic acid), using phosphorous pentoxide/methanesulfonic acid (PPMA) as condensing agent and solvent. By changing the reaction time and the amount of PPMA, Mw can be controlled in the range of 4.2 × 104 to 1.6 × 105. The polymer has been tested as a weak-acid catalyst and shows a certain catalytic activity for the hydrolysis of cellulose to glucose.

Catalytic Conversion of Renewable Sources for Biodiesel Production: A Comparison Between Biocatalysts and Inorganic Catalysts

This work compares the catalytic performance in biodiesel production of different kind of catalysts: acid, acid–base and biocatalysts. The inorganic catalysts tested have been: strong acid catalysts (USY, BEA, FAU-X), weak acid catalysts (MCM-41 and ITQ-6 with Si/Al = ∞), acid–base catalysts (K-MCM-41, K-ITQ-6), potassium silicate (K2SiO3) and hydroxide (KOH). The enzyme used as biocatalyst has been the Rhizomucor miehei Lipase. This enzyme has been immobilized in/on zeolite and related materials by different routes: adsorption, covalent binding, entrapment by sol–gel in mesoporous matrix or into liposome hybrid nanospheres. Among inorganic solid catalysts tested, the highest triglycerides conversion and biodiesel yield were achieved by K-ITQ-6 catalysts, after 48 h of reaction at 180 °C. Among heterogeneous biocatalysts, the type of lipase immobilization procedure strongly affects the final performance of the biocatalyst, especially toward its stability. The lipase encapsulated into the surfactant/mesoporous matrix or liposome nanospheres showed the best biodiesel productivity. The comparison among inorganic catalysts and biocatalysts tested reveals that the first type of catalysts requires much energy and alcohol consume in order to achieve the same substrate conversion, while the biodiesel yield strongly increases using biocatalyst, due to its high selectivity.

Benzene-Silica with Hexagonal and Cubic Ordered Mesostructures Synthesized in the Presence of Block Copolymers and Weak Acid Catalysts

Highly ordered mesoporous benzene–silicas with 2D hexagonal (p6mm) and 3D cubic (Im3m) symmetry were prepared using weaker acids than hydrochloric acid in the presence of Pluronic P123 and F127 triblock copolymer templates. The resulting ordered mesostructures of 1,4-bis(triethoxysilyl)benzene (BTEB) were well-organized when iron(III) chloride hexahydrate (weak Bronsted acid with Ka = 6.3 × 10–3) was employed; 2D hexagonal structure was obtained at the concentration exceeding 0.064 M (pH ≤1.76) and 3D cubic structure was obtained at the concentration about 0.112 M (pH ≤1.63). The specific surface areas and pore diameters of the hexagonal benzene–silicas studied were in the range from 707 to 966 m2 g–1 and from 7.5 to 8.2 nm, respectively; the corresponding values for cubic benzene–silicas were 514–604 m2 g–1 and 8.5–9.0 nm, respectively. Also, type IV nitrogen adsorption–desorption isotherms and very narrow pore size distributions were obtained for these materials, which are similar to those for mesoporou...

Synergy of boric acid and added salts in the catalytic dehydration of hexoses to 5-hydroxymethylfurfural in water

In combination with various salts boric acid, B(OH)3, was shown to be an efficient, weak Lewis acid catalyst in the aqueous dehydration of fructose to 5-hydroxymethylfurfural (HMF) due to strong complexation between the boron atom and the hexoses. In the dehydration of a highly concentrated aqueous fructose solution (30 wt%), a HMF yield of 60% was achieved at 92% fructose conversion and a HMF selectivity of 65% with 100 g L−1B(OH)3 and 50 g L−1sodium chloride in the aqueous phase and methyl-isobutylketone (MIBK) as extracting solvent. Furthermore, the dehydration of glucose resulted in a yield of 14% HMF at 41% glucose conversion after 5 h at similar conditions. These results are highly competitive with currently reported aqueous HMF dehydration systems. In combination with the non-corrosive and non-toxic nature of the boric acid, compared to other well known homogeneous catalysts applicable for the dehydration process (e.g., H2SO4 and HCl), clearly, the boric acid-salt mixture is a very attractive catalyst system.

Addition of Azomethine Ylides to Aldehydes: Mechanistic Dichotomy of Differentially Substituted α‐Imino Esters

AbstractThe formal 1,3‐dipolar cycloaddition of azomethine ylides and aldehydes is explored, as hydrolysis of the resulting oxazolidine product gives facile access to valuable syn‐β‐aryl‐β‐hydroxy‐α‐amino esters. The use of using benzaldehyde‐derived imines as the ylide precursor results in 1,3‐dipolar cycloaddition with high conversions but low diastereoselectivity. In contrast, the employment of benzophenone‐derived imines as the ylide precursor results in an aldol reaction, which gives the intermediate oxazolidine in high diastereoselectivity and requires a weak acid catalyst to achieve higher conversions.

Biodiesel production process by homogeneous/heterogeneous catalytic system using an acid–base catalyst

The transesterification of triglycerides contained in waste oilseed fruits with methanol has been studied in heterogeneous/homogeneous systems using acid and base catalysts. The acid catalysts (strong acid catalysts: USY, BEA, FAU-X, and weak acid catalysts: MCM-41 and ITQ-6 with Si/Al = ∞) were prepared by hydrothermal synthesis procedures. In order to obtain acid–base catalysts, potassium was loaded on different materials by ionic exchange (obtaining K-MCM-41, K-ITQ-6,). XRD, ICP-MS, IR after CO and CO 2 adsorption, thermal analyses and N 2 adsorption/desorption techniques have been used for catalysts characterization. The highest triglycerides conversion and biodiesel yield values were achieved by K-ITQ-6 catalysts, after 24 h of reaction at 180 °C. Deactivation of this catalyst occurs for potassium leaching, but its regeneration and reuse are feasible and easy to perform. A possible continuous biodiesel production process has been proposed.

Catalytic reaction of 1,3-butanediol over solid acids

Catalytic reaction of 1,3-butanediol over solid acids such as SiO 2–Al 2O 3, Al 2O 3, ZrO 2 and TiO 2 was investigated. The catalytic activities of these acids were in good coincidence with their acid properties: strong acid catalysts, SiO 2–Al 2O 3 and Al 2O 3, catalyzed dehydration of 1,3-butanediol at the reaction temperature below 250 °C, while weak acid catalysts, ZrO 2 and TiO 2, required the temperature above 325 °C to activate 1,3-butanediol. SiO 2–Al 2O 3 catalyzed the dehydration of 1,3-butanediol into unsaturated alcohols, and consecutively dehydrated them into 1,3-butadiene. 4-Methyl-1,3-dioxane, which is the acetal compound of 1,3-butanediol and formaldehyde, was obtained with high selectivity over Al 2O 3. Several compounds were produced over TiO 2 and ZrO 2 owing to the side reactions such as dehydrogenation and hydrogenation. The characteristics in the reaction were discussed in connection with other reactions of monoalcohols and of the produced unsaturated alcohols.

EFFICIENT PREPARATION OF 2-METHYL-1,3-DIOXOLANE-2-ETHANOL AND 2-(2-BROMOETHYL)-2- METHYL-1,3-DIOXOLANE FROM 4-HYDROXY-2-BUTANONE

ABSTRACT 2-Methyl-1,3-dioxolane-2-ethanol was prepared in 90% isolated yield from 4-hydroxy-2-butanone and ethylene glycol using a weak acid catalyst and ethyl acetate as the reaction solvent. 2-(2-Bromoethyl)-2-methyl-1,3-dioxolane was prepared in 75% isolated yield by bromination of 2-Methyl-1,3-dioxolane-2-ethanol with dibromotriphenylphosphorane. The reagent was prepared in situ by titrating triphenylphosphine with bromine at an ice–ethanol bath temperature. The target compounds are useful methyl vinyl ketone equivalents. * Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.

ChemInform Abstract: Lewis Acid‐Catalyzed Hetero‐Diels‐Alder Reactions of Readily Enolizable 1‐Oxa‐1,3‐dienes, 2‐Oxo‐3‐alkenylphosphonates, with Vinyl Ethers.

ChemInformVolume 20, Issue 48 Heterocyclic Compounds ChemInform Abstract: Lewis Acid-Catalyzed Hetero-Diels-Alder Reactions of Readily Enolizable 1-Oxa-1,3-dienes, 2-Oxo-3-alkenylphosphonates, with Vinyl Ethers. E. WADA, E. WADA Inst. Adv. Mat. Stud., Dep. Mol. Sci. Technol., Interdiscip. Grad. School Eng. Sci., Kyushu Univ., Kasugakoen, Kasuga 816, JapanSearch for more papers by this authorS. KANEMASA, S. KANEMASA Inst. Adv. Mat. Stud., Dep. Mol. Sci. Technol., Interdiscip. Grad. School Eng. Sci., Kyushu Univ., Kasugakoen, Kasuga 816, JapanSearch for more papers by this authorO. TSUGE, O. TSUGE Inst. Adv. Mat. Stud., Dep. Mol. Sci. Technol., Interdiscip. Grad. School Eng. Sci., Kyushu Univ., Kasugakoen, Kasuga 816, JapanSearch for more papers by this author E. WADA, E. WADA Inst. Adv. Mat. Stud., Dep. Mol. Sci. Technol., Interdiscip. Grad. School Eng. Sci., Kyushu Univ., Kasugakoen, Kasuga 816, JapanSearch for more papers by this authorS. KANEMASA, S. KANEMASA Inst. Adv. Mat. Stud., Dep. Mol. Sci. Technol., Interdiscip. Grad. School Eng. Sci., Kyushu Univ., Kasugakoen, Kasuga 816, JapanSearch for more papers by this authorO. TSUGE, O. TSUGE Inst. Adv. Mat. Stud., Dep. Mol. Sci. Technol., Interdiscip. Grad. School Eng. Sci., Kyushu Univ., Kasugakoen, Kasuga 816, JapanSearch for more papers by this author First published: November 28, 1989 https://doi.org/10.1002/chin.198948179Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue48November 28, 1989 RelatedInformation

Lewis Acid-Catalyzed Hetero Diels–Alder Reactions of Readily Enolizable 1-Oxa-1,3-dienes, 2-Oxo-3-alkenylphosphonates, with Vinyl Ethers

Abstract Remarkable rate enhancement is achieved by use of a weak Lewis acid catalyst such as zinc chloride or bromide in the hetero Diels–Alder reactions of 2-oxo-3-alkenylphosphonates as readily enolizable 1-oxa-1,3-dienes with vinyl ethers. Highly endo-selective cyclo-adducts, 2,4-cis-3,4-dihydro-2H-pyrans, are produced in good yields.