Biodiesel production via esterification of oleic acid catalyzed by MnO2@Mn(btc) as a novel and heterogeneous catalyst

The main objective of this study is to develop efficient and environmentally benign heterogeneous catalysts for biodiesel production. For this purpose, a heterogeneous MnO₂@Mn(btc) catalyst was prepared by the solvothermal method, and the prepared catalyst was tested for the esterification of oleic acid. Various techniques such as X‐ray diffraction, scanning and transmission electron microscopy, Brunauer–Emmett–Teller (BET) method, infrared spectroscopy, thermogravimetry, and NH₃‐TPD (temperature programmed desorption) analysis were employed for the characterization of the solid catalyst. The solid catalyst with MnO₂@Mn(btc) loading of 15% showed high catalytic activity and long durability in the esterification of oleic acid, in which the fatty acid methyl ester yield reached 98% consecutively for at least five cycles under mild conditions.     

Biotransformation of ursolic acid by Alternaria longipes AS3.2875

Microbial transformation of ursolic acid (1) was carried out by Alternaria longipes AS 3.2875. Six transformed products (2–7) from 1 were isolated and their structures were identified as 3-carbonyl ursolic acid 28-O-β-D-glucopyranosyl ester (2), ursolic acid 3-O-β-D-glucopyranoside (3), ursolic acid 28-O-β-D-glucopyranosyl ester (4), 2α, 3β-dihydroxy ursolic acid 28-O-β-D-glucopyranosyl ester (5), 3β, 21β dihydroxy ursolic acid 28-O-β-D-glucopyranosyl ester (6), and 3-O-(β-D-glucopyranosyl)- ursolic acid 28-O-(β-D-glucopyranosyl) ester (7) based on the analysis of 1D NMR, 2DNMR and MS data. The product 2 was a new compound among them and showed stronger antibacterial activity against S. aureu, MRSA and MRCA than substrate. In this study, we modified structure of ursolic acid through biotransformation to enhance its activities and preliminarily discussed the transformation way of the products.     

The cis–trans transformation of cyclohexane formic acid ester compounds

Trans-alkyl cyclohexane formic acid phenol ester compounds are synthesised by reaction of trans-cyclohexane formic acid and phenols. This process also produces many harmful cis-alkyl cyclohexane formic acid phenol ester compounds that are harmful to the environment. Using p-toluenesulphonic acid as the catalyst in this experiment, these cis compounds were transformed to their trans form. The yields of trans-alkyl cyclohexane formic acid phenol ester compounds were more than 70%, which was significantly higher when compared to the yields of 40–60% obtained using the control method. The effects of catalyst, reaction time and reaction temperature on cis–trans transformation were investigated. The possible mechanism of cis–trans transformation has been discussed in this report.     

A novel route for synthesizing esters and polyesters from the Diels-Alder adduct of levopimaric acid and acrylic acid

A novel route for the esterification of the Diels-Alder adduct between abietic acid, in its isomer form of levopimaric acid, and acrylic acid was established. The high purity Diels-Alder adduct was prepared starting from rosin acids. When the adduct was subjected to a condensation reaction in the presence of a cyclic carbonate ester and of an efficient amine catalyst, hydroxyalkyl esters were obtained. The corresponding linear polyesters were synthesized by the advanced polycondensation of the above intermediates at high temperature, under vacuum, and in the presence of some adequate polyesterification catalysts. In the work 1,3-dioxolan-2-one as cyclic carbonate ester, triethylamine as esterification catalyst, and toluene-4-sulfonic acid monohydrate or tetrabutyl titanate as polycondensation catalysts, were preferred for exemplifications. The polyesters were soluble in dimethylacetamide, trichloromethane, tetrahydrofuran, 1,1,2,2-tetrachloroethane, or 1,4-dioxane. The thermal and electric studies showed that the polymers were substances with good thermal stability and high dielectric properties.     

Highly efficient heterogeneous acylations of aromatic compounds with acid anhydrides and carboxylic acids by montmorillonite-enwrapped titanium as a solid acid catalyst

Montmorillonite-enwrapped titanium hydroxide species (Ti⁴⁺-mont) acted as a highly efficient heterogeneous acid catalyst for the acylation of aromatic compounds with acid anhydrides or carboxylic acids. The catalytic activity of the Ti⁴⁺-mont was higher than those of other acid catalysts such as zeolites, SO ₄ ²⁻ /ZrO₂ and p-toluenesulfonic acid. For example, the reaction of anisole with dodecanoic acid in the presence of the Ti⁴⁺-mont catalyst gave 1-(4-methoxyphenyl)-1-dodecanone in 97% yield. Furthermore, the Ti⁴⁺-mont catalyst was easily separated from the reaction mixture and was recyclable.     

Hydrogenation of 2,4-hexadienoic acid methyl ester

Hydrogenation of 2,4-hexadienoic acid methyl ester on supported metal catalysts (Pd/C, Pt/C, Rh/C and Ru/C) has been investigated. Methyl esters of 2-hexenoic and 3-hexenoic acids were formed and further hydrogenated to the methyl ester of hexanoic acid. Palladium was found to be the most active and selective catalyst for this reaction owing to the formation of intermediates.     

FT-IR Determination of degree of esterification in polycarboxylic acid cross-link finishing of cotton

Cross-linking of cotton with polycarboxylic acids, applied with catalysts based on phosphorus-containing inorganic acids, produces fabrics with excellent smooth-drying properties and which release no formaldehyde at any stage of preparation or on storage. The reaction produces cellulose ester linkages and unreacted carboxylic acid groups. Fourier transform infrared spectroscopy was used to determine the degree of esterification of polycarboxylic acids that occurred on cross-linking of cotton. The height of the carbonyl peak at 1730 cm ^–1 was determined on the same treated fabrics after soaking in dilute acid to convert ionized groups to free acid and then in dilute base to convert free acid to carboxylate ion. The carbonyl peak for the base rinsed fabric (ester only) was ratioed against the same peak for the acid-rinsed fabric (total carbonyl, ester plus acid) to obtain a measure of the degree of esterification. This ratio minimizes the problems of different molar extinction coefficients that are encountered when peaks from different functional groups are used.     

Pd(II)-catalyzed vinylic polymerization of norbornene and copolymerization with norbornene and copolymerization with norbornene carboxylic acid esters

The vinylic polymerization of norbornene and its copolymerization with norbornene carboxylic acid methyl esters were investigated. Norbornene was polymerized by us using di-μ-chloro-bis-(6-methoxybicyclo[2.2.1]hept-2-ene-endo-5σ,2π)-palladium(II) as catalyst. The polymerization time can be decreased by a factor of 100000 by activation of the catalyst with methylaluminoxane (MAO). With this palladium catalyst activated by MAO, 140 t of norbornene can be polymerized per mol palladium per h. This catalyst system was much more active than [Pd(CH₃CN)₄](BF₄)₂ ( I ). The polymerization of norbornene by (6-methoxybicyclo[2.2.1]hept-2-ene-endo-5σ,2π)-palladium(II) tetrafluoroborate was also possible but it was not as fast as the polymerization by Pd catalysts activated with MAO. We were also able to obtain copolymers of norbornene and 5-norbornene-2-carboxylic acid methyl ester (exo/endo = 1/4 or 2/3) containing between 15 and 20 mol-% ester units. The copolymerization of norbornene and 2-methyl-5-norbornene-2-carboxylic acid methyl ester (exo/endo = 7/3) was faster than the copolymerization mentioned before. In contrast the homopolymerization of 2-methyl-5-norbornene-2-carboxylic acid methyl ester was 10 times slower than that of 5-norbornene-2-carboxylic acid methyl ester (exo/endo = 1/4).     

Microbial hydroxylation and glycosidation of oleanolic acid by Circinella muscae and their anti-inflammatory activities

Biotransformation of oleanolic acid (OA) by Circinella muscae AS 3.2695 was investigated. Nine hydroxylated and glycosylated metabolites (1–9) were obtained. Their structures were elucidated as 3β,7β-dihydroxyolean-12-en-28-oic acid (1), 3β,7β,21β-trihydroxyolean-12-en-28-oic acid (2), 3β,7α,21β-trihydroxyolean-12-en- 28-oic acid (3), 3β,7β,15α-trihydroxyolean-12-en-28-oic acid (4), 7β,15α-dihydroxy- 3-oxo-olean-12-en-28-oic acid (5), 7β-hydroxy-3-oxo-olean-12-en-28-oic acid (6), oleanolic acid-28-O-β-D-glucopyranosyl ester (7), 3β,21β-dihydroxyolean-12-en-28- oic acid-28-O-β-D-glucopyranosyl ester (8), and 3β,7β,15α-trihydroxyolean-12-en- 28-oic acid-28-O-β-D-glucopyranosyl ester (9) by spectroscopic analysis. Among them, compounds 4 and 9 were new compounds. In addition, anti-inflammatory activities were assayed and evaluated for the isolated metabolites. Most of the metabolites exhibited significant inhibitory activities on lipopolysaccharides-induced NO production in RAW 264.7 cells.     

Efficient atom-economic one-pot multicomponent synthesis of benzylpyrazolyl coumarins and novel pyrano[2,3-c]pyrazoles catalysed by 2-aminoethanesulfonic acid (taurine) as a bio-organic catalyst

The present work describes eco-friendly multicomponent protocol for the synthesis in excellent yields of structurally diverse benzylpyrazolyl coumarin 5 (a–s) involving the reaction of 4-hydroxycoumarin, ethyl acetoacetate, hydrazine hydrate/phenyl hydrazine hydrate and aldehydes, also novel pyrano[2,3-c]pyrazole derivatives 8 (a–k) integrated by isonicotinic acid hydrazide from reaction of aldehyde, ethyl acetoacetate, malononitrile with isoniazid, employing water as a reaction medium and 2-aminoethanesulfonic acid (taurine) as the catalyst. This new methodology endowed the advantages such as short reaction time, recovery of catalysts after catalytic reaction and reusing them without losing their activity and alleviate of operation.     

新型磁性纳米固体酸催化剂ZrO2/Fe3O4的制备及表征

根据将磁性一材料和固体酸进行组装的设想，成功制备了磁性纳米固体酸催化剂。纳米级样性前体-磁基体(Fe3O4)的磁性、粒子尺寸受到Fe^2^+/Fe^3^+投料比和用于沉淀的NaOH浓度的显著影响；不同复合方法也对磁性固体酸催化剂ZrO2/Fe3O4的酯化催化性能影响显著。XRD，XPS，TEM，比表面积测定，元素组成分析及磁学性能测定等表征结果证实，新型催化剂以磁性材料为核，固体酸催化剂活性组分包覆在其外部形成包覆型的磁性纳米催化剂。该系列催化剂均具有较小的粒子尺寸、较强的磁性及较高的酯化催化活性；并且易于通过磁场进行回收，使用寿命较长。它们对乙酸与正丁醇酯化反应的催化活性随着ZrO2含量增加而提高。催化剂中ZrO2的晶化温度因为Fe3O4的存在而升高，有利于催化剂活性的保持，热处理温度会对催化剂的磁性及催化活性产生影响。     

Convenient preparation of highly active phase-transfer catalyst for catalytic asymmetric synthesis of α-alkyl- and α,α-dialkyl-α-amino acids: application to the short asymmetric synthesis of BIRT-377

A highly active phase-transfer catalyst was conveniently prepared from the known, easily available (S)-4,5,6,4′,5′,6′-hexamethoxybiphenyldicarboxylic acid. This catalyst exhibited the high catalytic performance (0.01-1 mol %) in the asymmetric alkylation of N-(diphenylmethylene)glycine tert-butyl ester and N-(p-chlorophenylmethylene)alanine tert-butyl ester compared to the existing chiral phase-transfer catalysts, thereby allowing to realize a general and useful procedure for highly practical enantioselective synthesis of structurally diverse natural and unnatural α-alkyl-α-amino acids as well as α,α-dialkyl-α-amino acids.     

耐水性共功能化介孔SBA-15的制备及其在甘油与乙酸酯化反应中的应用

通过后嫁接法合成了一系列耐水性的丙烷磺酸和正辛基共功能化的介孔SBA-15催化剂.采用BET、XRD、FT-IR、TG、TEM及酸碱滴定的方法对催化剂进行了结构性能表征,并将其应用在丙三醇和乙酸的酯化反应中.Octyl-PrSO₃H-SBA-15由于较高的酸量以及极好的耐水性而在丙三醇和乙酸酯化反应中取得了100%的丙三醇转化率和89.9%的甘油二乙酸酯和三乙酸酯收率.对影响丙三醇转化率和产物选择性的反应温度、反应时间、催化剂量及反应物比例等进行了讨论.通过向反应体系中加入一定量额外的水对功能化的催化剂的耐水性进行了考察.催化剂Octyl-PrSO₃H-SBA-15具有比PrSO₃H-SBA-15更好的耐水性能,并且对该催化剂Octyl-PrSO₃H-SBA-15在循环使用9次以后,其催化活性基本保持不变.     

Addition of thiols to ethyl 4,4,4-trifluorocrotonate

Ethyl 4,4,4-trifluorocrotonate 1 readily adds aliphatic and aromatic thiols and aminothiols at the double bond in the presence of catalytic amounts of alkylamines and ammonia to give 3-thiolation products. Thiolacetic acid reacts with ester 1 in the absence of a catalyst at 100 °C.     

Cr掺杂的丙烷选择氧化制丙烯酸高效催化剂

在丙烷选择氧化制丙烯酸催化剂MoVTeNbOx的活性相M1基础上掺杂一定量的Cr,当Cr/Nb摩尔比为0.002时,催化剂具有很高的丙烯酸选择性(78.3%)和收率(50.7%);并采用X射线衍射、X射线光电子能谱、程序升温还原、O2程序升温脱附、NH3程序升温脱附和异丙醇氧化等手段对催化剂的构效关系进行了探讨.结果表明,适量Cr的添加可调节催化剂表面Mo6+,V5+和Te4+等物种含量,提高催化剂的氧化能力,使丙烷转化率增加.同时,适量Cr的添加使得催化剂表面酸强度下降,酸性位点数量减少,从而抑制丙烯酸的深度氧化,提高了丙烯酸选择性.     

磺酸官能化的磁性核壳结构的纳米材料用于果糖脱水制备5-羟甲基糠醛(英)

通过反相微乳液法制备了以Fe₃O₄为核,磺酸官能化的硅基材料为壳层的磁性酸性催化剂.首先制备纳米Fe₃O₄磁核,然后涂层包覆苯基修饰的纳米级硅层,最后进行苯基磺化修饰,制得固体酸催化剂Fe₃O₄@Si/Ph-SO₃H.在果糖脱水制备5-羟甲基糠醛反应中,该催化剂表现出较好的催化活性,优于传统催化剂A-15,且与均相无机酸催化活性相当.当采用二甲基亚砜作溶剂,在110℃下反应3 h,果糖转化率达到99%,5-羟甲基糠醛收率为82%.另外,该催化剂经磁法回收后可多次重复使用.     

Heterogeneous soft acid catalysis of the sucrose hydrolysis

Using a micro-calorimetrical DSC we have compared the acid-catalyzed inversion of sucrose in homogeneous and heterogeneous systems. Acetic acid was chosen as catalyst for homogeneous system, and several carboxylic cationites were used as heterogeneous catalysts. The kinetic apparent parameters (A, E, k _ap) for all the systems were calculated from DSC data with Friedmann’s method and catalytic constant, k₃₂₃^cat, was further inferred. We found that the specific catalyst efficiency, q _cat, in heterogeneous system is over 5000 times higher than in case of homogeneous ones. The activity of heterogeneous carboxylic systems is still about 30 times larger than those of a strong mineral acid in homogeneous catalysis. The results indicate the high efficiency of heterogeneous systems for soft acid catalysis of the sucrose hydrolysis.     

Development of an efficient method for preparation of 1,3,5-trihydroxyisocyanuric acid (THICA) and its use as aerobic oxidation catalyst

1,3,5-Trihydroxyisocyanuric acid (THICA), which serves as an efficient radical-producing catalyst from hydrocarbons, was successfully prepared by two methods. The reaction of O-benzylhydroxyamine with phenyl chloroformate gave formbenzyloxycarbamic acid phenyl ester of which subsequent treatment with dimethylaminopyridine (DMAP) produced 1,3,5-tribenzyloxyisocyanurate leading to THICA by hydrogenation with H₂ on Pd/C. The other method involved the direct synthesis of 1,3,5-tribenzyloxyisocyanurate from O-benzylhydroxyamine and diphenyl carbonate. The aerobic oxidation of p-methylanisole catalyzed using THICA as a key catalyst afforded p-anisic acid in almost quantitative yield (>99%).     

Phosphine-Free Suzuki Cross-Coupling Reaction Using an Efficient and Reusable Pd Catalyst in an Aqueous Medium Under Microwave Irradiation

Abstract

We report here an improved, highly efficient, and general method for the ligand-free Suzuki cross-coupling reaction to the synthesis of biaryls, bipyridyls, thienylpyridine, and allylphenols. Microwave irradiation of (het)aryl halides and (hetaryl, allyl)arylboronic acid N-methyl-iminodiacetic acid (MIDA) ester, using polyurea microencapsulated palladium catalyst (Pd EnCat 30), gave the coupling adducts 1a–x in excellent yields in just 10–18 min.