Efficient synthesis of 1,3-dioxanes catalyzed by trifluoromethanesulfonic acid using formalin as formaldehyde source

Prins cyclizations of styrene derivatives were smoothly conducted in a water solution of formaldehyde using trifluoromethanesulfonic acid (TfOH) as catalyst. While excellent yield was obtained in the Prins cyclization of styrene in the presence of TfOH, low yields or no reaction were observed when other traditional minimal acids catalysts were used.     

光刻胶用环化聚异戊二烯的研制

研究了顺１，４聚异戊二烯在二甲苯溶剂中在酸性复合催化剂ＳｎＣｌ４／ＰＴＳＡ存在下的环化反应。发现复合催化剂可在较低的温度下引发聚异戊二烯的环化反应，且可抑制聚合物的降解反应，找到了复合催化剂的最佳组成。制得了适用于光刻胶制造的环化聚异戊二烯。     

Diels–Alder reactions of carbonyl-containing dienophiles catalyzed by tungstophosphoric acid supported on silica gel

Tungstophosphoric acid (H₃PW₁₂O₄₀) supported on silica gel proved to be an active heterogeneous catalyst for Diels–Alder reactions of enones with various dienes. The Diels–Alder adducts were formed in high regio- and/or stereoselectivity. In some cases the Diels–Alder reactions were accompanied by competing polymerization of the starting compounds. We also found that trifluoromethanesulfonic acid (triflic acid) is an effective homogeneous catalyst for the reaction of unprotected but-3-en-2-one (methyl vinyl ketone) with 1,3-cyclohexadiene, albeit with a lower activity than tungstophosphoric acid. This revised version was published online in July 2006 with corrections to the Cover Date.     

Trifluoromethanesulfonic Acid‐Catalyzed Tandem Semi‐Pinacol Rearrangement/Alkyne‐Aldehyde Metathesis Reaction of Arylpropagylsulfonamide‐Tethered 2,3‐Epoxycyclohexan‐1‐ols to Spiropiperidines

A simple and efficient trifluoromethanesulfonic acid‐catalyzed cycloisomerization of arylpropagylsulfonamide‐tethered 2,3‐epoxycyclohexan‐1‐ols is described. The cyclization proceeds via tandem semi‐pinacol rearrangement/alkyne‐aldehyde metathesis to afford spiropiperidines under mild reaction conditions.     

Hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber catalyzed by [Ir(COD)py(PCy3)]PF6

In the presence of chlorinated solvents, the catalytic complex [Ir(COD)py(PCy₃)]PF₆ (where COD is 1,5‐cyclooctadiene and py is pyridine) was an active catalyst for the hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber. Detailed kinetic and mechanistic studies for homogeneous hydrogenation were carried out through the monitoring of the amount of hydrogen consumed during the reaction. The final degree of olefin conversion, measured with a computer‐controlled gas‐uptake apparatus, was confirmed by Fourier transform infrared spectroscopy and ¹H‐NMR spectroscopy. Synthetic cis‐1,4‐polyisoprene was used as a model polymer for natural rubber without impurities to study the influence of the catalyst loading, polymer concentration, hydrogen pressure, and reaction temperature with a statistical design framework. The kinetic results for the hydrogenation of both synthetic cis‐1,4‐polyisoprene and natural rubber indicated that the hydrogenation rate exhibited a first‐order dependence on the catalyst concentration and hydrogen pressure. Because of impurities inside the natural rubber, the hydrogenation of natural rubber showed an inverse behavior dependence on the rubber concentration, whereas the hydrogenation rate of synthetic rubber, that is, cis‐1,4‐polyisoprene, remained constant when the rubber concentration increased. The hydrogenation rate was also dependent on the reaction temperature. The apparent activation energies for the hydrogenation of synthetic cis‐1,4‐polyisoprene and natural rubber were evaluated to be 79.8 and 75.6 kJ/mol, respectively. The mechanistic aspects of these catalytic processes were discussed on the basis of observed kinetic results. The addition of some acids showed an effect on the hydrogenation rate of both rubbers. The thermal properties of hydrogenated rubber samples were determined and indicated that hydrogenation increased the thermal stability of the hydrogenated rubber but did not affect the inherent glass‐transition temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4219–4233, 2006     

三氟甲磺酸催化便捷高效合成2,4-滴丁酯除草剂

以2,4-二氯苯氧乙酸与正丁醇为原料,三氟甲磺酸为催化剂,催化合成2,4-滴丁酯,考察了醇酸摩尔比、反应时间及催化剂用量等对反应的影响。结果表明,合成2,4-滴丁酯的最佳反应条件是:正丁醇与2,4-二氯苯氧乙酸的摩尔比为3∶1,催化剂用量为0.2%(占2,4-二氯苯氧乙酸摩尔量),回流反应8 h,在此条件下,酯化率达97.1%。     

Preparation of copolymer of L‐aspartic acid and L‐glutamic acid

In this article, a new copolymer of L ‐aspartic acid and L ‐glutamic acid, which may be a biodegradable high molecular polymer and can be used more widely in many areas, was synthesized. The conditions of preparation, such as catalyst, reaction time, reaction temperature, the amount of catalyst, the times of adding catalyst, and the molar ratio of L ‐aspartic acid to L ‐glutamic acid, were optimized. The copolymer was characterized by ¹³C NMR, infrared spectroscopy, and X‐ray diffractometer. The molecular weight was determined by GPC. The result indicated that production yield, purity of product, and molecular weight of product increased with amount of catalyst and molar ratio of L ‐aspartic acid to L ‐glutamic acid increasing. The best condition of preparation was the following: reacting 2–4 h at the temperature of 180–200°C. The product yield with the molecular weight 13,000.00 reached 63.2% and the purity of product was 96.33% when the copolymerization was carried out at the temperature of 200°C under vacuum for 2 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3626–3633, 2006     

三氟甲磺酸催化1-己烯齐聚反应的研究

使用三氟甲磺酸作催化剂对1-己烯齐聚反应进行研究。考察三氟甲磺酸催化剂用量、反应温度和反应时间等工艺条件对产物聚α-烯烃收率的影响。确定了最佳工艺条件：催化剂用量1.0 mL，反应温度50 ℃，反应时间3 h，此条件下，1-己烯转化率约为90%，产物主要是二聚物、三聚物、四聚物和五聚物，没有裂解产品。为进一步工业化开发聚α-烯烃合成油提供了基础数据。     

Hydrogenation of cis‐1,4‐polyisoprene catalyzed by Ru(CHCH(Ph))Cl(CO)(PCy3)2

Hydrogenation is a useful method which has been used to improve oxidative and thermal degradation resistance of diene‐based polymers. The quantitative hydrogenation of cis‐1,4‐polyisoprene which leads to an alternating ethylene–propylene copolymer was studied in the present investigation. To examine the influence of key factors on the reaction, such as catalyst concentration, polymer concentration, hydrogen pressure, and temperature, a detailed study of the hydrogenation of cis‐1,4‐polyisoprene catalyzed by the Ru complex, Ru(CH?CH(Ph))Cl(CO)(PCy₃)₂ was carried out by monitoring the amount of hydrogen consumed. Infrared and ¹H‐NMR spectroscopic measurements confirmed the final degree of hydrogenation. The hydrogenation of cis‐1,4‐polyisoprene followed pseudo‐first‐order kinetics in double‐bond concentration up to high conversions of double bond, under all sets of conditions studied. The kinetic results suggested a first‐order behavior with respect to total catalyst concentration as well as with respect to hydrogen pressure. The apparent activation energy for the hydrogenation process, obtained from an Arrhenius plot, was 51.1 kJ mol^?1 over the temperature range of 130 to 180°C. Mechanistic aspects of the catalytic process are discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3259–3273, 2004     

Microstructure of a Pd/ceria–zirconia catalyst after high-temperature aging

Ga/ZSM-5 is an effective catalyst for the conversion of dilute (3%) ethylene-in-methane reactant streams into aromatic hydrocarbons at 500–550°C. A Ga loading as low as 0.5 wt% is sufficient to obtain maximum yields of aromatic products. At 520°C, an ethylene conversion of 93%, with an aromatics selectivity of 81%, was obtained over a 5 wt% Ga/ZSM-5 catalyst. The conversion of ethylene into aromatics over Ga/ZSM-5 catalysts involves a complex sequence of oligomerization, isomerization, cracking, and cyclization reactions that occur on Brønsted acid zeolites in the zeolite. The role of the gallium, which exists as both Ga³⁺ at zeolitic exchange sites and as Ga₂O₃ within the channels and on the external surface of the calcined catalyst, is to promote dehydrogenation of the acid-catalyzed oligomerization and cyclization products.     

三氟甲磺酸催化合成柠檬酸酯

利用一种新型高效绿色催化剂三氟甲磺酸(CF3SO3H)合成绿色增塑剂柠檬酸三丁酯,结果表明该催化剂用量少(占柠檬酸的0.1%),反应时间短(5 h)。研究了该催化剂合成乙酰柠檬酸酯的一体化工艺,实现了无须精制柠檬酸三丁酯,直接从柠檬酸出发制得乙酰柠檬酸三丁酯,产率高(两步87.1%),纯度高(99.1%),大幅简化了生产工艺和成本且环保,适合工业化。同时,研究了CF3SO3H催化合成丙酰、丁酰柠檬酸酯类产品的一体化工艺。     

Oxidative Cycloaddition of Aldoximes with Maleimides using Catalytic Hydroxy(aryl)iodonium Species

A mild catalytic procedure for the efficient oxidative cyclization of aldoximes with maleimides mediated by hypervalent iodine(III) active species has been developed. This catalytic cyclization affords the corresponding pyrrolo‐isoxazole products in generally good yields. The catalytic cycle involves active hydroxy(aryl)iodonium species generated in situ from 2‐iodobenzoic acid as precatalyst and m‐chloroperoxybenzoic acid (m‐CPBA) as terminal oxidant in the presence of trifluoromethanesulfonic acid. The presence of active hydroxy(aryl)iodonium species in this reaction has been confirmed by ESI‐mass spectrometry and ¹H NMR spectroscopy.

     

Coking and regeneration of palladium-doped H3PW12O40/SiO2 catalysts

The coking during propene oligomerisation and subsequent regeneration of both silica-supported heteropoly acid H₃PW₁₂O₄₀ (PW) and its palladium-modified form (1.6–2.5 wt% Pd) have been studied. ³¹P MAS NMR studies have revealed that the Keggin structure of the catalyst was unaffected by coke deposition in both unmodified PW/SiO₂ and Pd-modified form. As shown by ¹³C MAS NMR and TGA/TPO, the Pd modification affects the nature of the coke formed: for the standard catalyst (PW/SiO₂) both soft coke, comprising mainly high molecular weight aliphatic oligomers, and hard coke, comprising polynuclear aromatics, are formed whilst on the Pd-modified catalyst only the soft coke is observed. Coke formation causes strong deactivation of the catalyst in the oligomerisation of propene. The aerobic burning of coke on the unmodified PW/SiO₂ occurs in the temperature range of 470–520°C. Doping the catalyst with Pd significantly decreases this temperature to allow catalyst regeneration at temperatures as low as 350°C without loss of catalytic activity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation and characterization of cyclic polyesters from ring‐chain reactions of poly(oxyepichlorhydrin oxymaloyl)

In this article, the synthesis and characterization of cyclic polyesters of poly(oxyepichlorhydrin oxymaloyl) from a ring‐chain reaction induced by “Maghnite,” an acid‐exchanged montmorillonite as acid solid ecocatalyst (Mag‐H⁺), is described. Maghnite is already used as catalyst for polymerization of many vinylic and heterocyclic monomers [Belbachir, U.S. Pat. 066969.0101 (2001)]. The reactions were monitored by gel permeation chromatography and ¹H‐NMR spectroscopy and the existence of cyclic species was proven. The effect of the amount of catalyst on yield and molecular weight of polymer was studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1240–1243, 2006     

基于F-C反应的天然产物大豆黄素合成工艺

引言 大豆黄素(又名大豆苷元、大豆黄酮,daid-zein),化学名为4',7-二羟基异黄酮,是从大豆中提取得到的一种异黄酮活性组分,是大豆异黄酮的一种,属大豆苷类中的游离型的苷元,因豆科植物中的大豆异黄酮大多以糖苷形式存在,故以游离型苷元形式存在的大豆黄素在豆科植物中的含量非常低,大约为0.1%,提取、分离过程都很困难,存在生产成本高、投资较大、工艺复杂、产品纯度低等问题.大豆黄素及其糖苷的结构如下     

环保型阻垢剂PESA的合成及阻硫酸盐垢性能研究

以马来酸酐为原料,钨酸钠为催化剂,双氧水为氧化剂,氢氧化钙为引发剂,采用溶液聚合法合成了聚环氧琥珀酸。研究了催化剂用量、环化pH、引发剂用量、聚合温度和聚合时间对PESA阻BaSO4垢性能的影响,并用原子吸收分光光度法对在最佳工艺条件下合成的产品进行了阻垢性能评价。结果表明,合成PESA的最佳工艺条件为马来酸酐9.8 g,催化剂用量0.33 g,环化pH为4,引发剂加量0.5 g,聚合温度82℃,聚合时间2 h。当PESA加量为8 mg/L时,对硫酸钡的阻垢率达98.0%;当PESA加量为40 mg/L时,对硫酸锶的阻垢率达90.4%。     

A novel palladium complex catalyst for carbonylation of alkynes under mild conditions

Carbonylation of alkynes has been carried out using a catalyst system consisting of Pd(OAc)₂, a monophosphine, p‐toluene sulphonic acid and semilabile anionic bidentate ligands such as pyridine or piperidine carboxylic acids. Turnover frequencies (TOF) upto 3500 h⁻¹ and 98% selectivity to 2‐substituted 2‐propenoic acid/ester have been achieved under mild CO pressures of 1–3 atm at 373 K. This revised version was published online in July 2006 with corrections to the Cover Date.     

PTSA/H3PO4复合酸催化合成尿囊素的研究

以一水乙醛酸和尿素为原料,在催化剂存在下,经环化缩合反应制备了医药和有机合成中间体及日化助剂尿囊素。研究表明,以对甲基苯磺酸-磷酸(PTSA-H3PO4)构成的复合酸作为催化剂,在75～80°C下环化反应6h,尿囊素收率可达60%以上。产品经元素分析,熔点测定、红外光谱表征并用滴定法测定其纯度,尿囊素含量在98%以上。     

生物质甘油制备环氧氯丙烷的研究

研究了以生物质甘油为原料通过氯代与环化2步制备环氧氯丙烷。考察了磺酸树脂、硫酸、磷酸、乙酸和己二酸等为催化剂时,时间、温度和催化剂用量对中间产物二氯丙醇的收率以及反应速率的影响,并对其催化机理进行了探讨。结果表明：以己二酸和乙腈组合为催化剂的催化效果最好。在环化反应生成环氧氯丙烷中,考察了水、甲苯、正丁醚、正辛醇和二氯...     

Synthesis and properties of photosensitive rubbers. IV. Photosensitive rubbers from hydroxyethyl cinnamate and polyisoprene modified with maleic anhydride

Polyisoprene in o-dichlorobenzene solution were reacted with maleic anhydride at 180°C under nitrogen atmosphere to form modified polyisoprene with α-substituted succinic anhydride groups. These groups were converted by reaction with hydroxyethyl cinnamate in pyridine at 25°C to cinnamate groups. Various amounts of cinnamate groups as photosensitive groups could be easily introduced into polyisoprene up to 75 mol % toward polyisoprene repeating units. Polymer glass transition temperatures of the products rose linearly from ?70°C for polyisoprene to 60°C with increasing amounts of the side groups. The solution viscosity of the products in chloroform decreased from 9.34 for polyisoprene to 0.77 with increasing amounts of the side groups. The photosensitivity of the polyisoprene, which is based on the photodimerization of the cinnamate groups, was higher than that of polypentenamer having cinnamate groups due to the interaction by the free carboxylic acids neighboring with the cinnamate groups. The photosensitivity of the cinnamate group was kinetically evaluated in terms of the dependence on the polymer glass transition temperature. The interaction by the free carboxylic acid groups in the polyisoprene reduced the dependence of the photosensitivity on the mobility of the polymer segments. Linear relationship between observed rate constants of the photodimerization and (T_UV ? T_g + 50)^?1 was obtained and the slope of the line changed and became very small at higher glass transition temperatures.