Regioselective and green synthesis of nitro aromatic compounds using polymer‐supported sodium nitrite/KHSO4

Polymer supported reagents have become the subject of considerable and increasing interest as insoluble materials in the organic synthesis. Use of polymeric reagents simplifies routine nitration of aromatic compounds because it eliminates traditional purification. In this article, the use of readily available cross‐linked poly(4‐vinylpyridine) supported sodium nitrite, [P₄‐Me] NO₂, as an efficient polymeric nitrating agent in the presence of KHSO₄ is described. A good range of available aromatic compounds were also subjected to nitration in the presence of [P₄‐Me] NO₂/KHSO₄. This reagent is regioselective and chemoselective nitrating polymeric reagent for activated aromatic rings. In this procedure, the work‐up is easy, and the spent polymeric reagent is easily regenerated and reused. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

氯苯硝化反应用固体酸催化剂的制备

用离子交换法制备了改性的Y型分子筛，考察了制备条件对其催化氯苯硝化反应活性的影响，并与其他固体酸催化剂进行了比较。结果表明，实验制备的催化剂硝化氯苯反应收率可达54%。该催化剂制备简单，催化活性好，可得到较高的对/邻硝基氯苯质量比，后处理简单，不腐蚀设备，无环境污染。     

Synthesis of azo chromophores by using a polymer‐supported sodium nitrite

Polymer supported reagents especially anion exchange resins have been widely applied in organic synthesis. The recent developments in polymer‐supported reactions have led to the propagation of combinatorial chemistry as a method for the rapid and efficient preparation of novel functionalized molecules. An interesting and fast growing branch of this area is polymer‐supported reagents. In this study, diazonium salts are generated and are coupled with a coupling component by using a polymer supported nitrite and a polymeric acid. In this procedure, the azo chromophores are formed in a clean and efficient manner, the work‐up is easy and yields are high to excellent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Diazotization of anilines and diazo coupling with a coupling component mediated by a polymer‐supported sodium nitrite and a polymeric acid

Polymer‐supported reagents have become the subject of considerable and increasing interest as insoluble materials in the organic synthesis. In this study, diazonium salts are generated and are coupled with a coupling component by using a polymer supported nitrite and a polymeric acid. In this procedure, the azo chromophores are formed in a clean and efficient manner, the work–up is easy and yields are high to excellent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A convenient synthesis of macroporous polymer‐supported supernucleophilic reagent and linear macromolecules

N,N′‐Bis(4‐pyridinyl)piperazine and N‐(4‐pyridinyl)piperazine have been prepared by treatment of piperazine with 4‐chloropyridine. N,N′‐Bis(4‐pyridinyl)piperazine (bis‐DMAP) is similar to a couple of 4‐(N,N‐dimethylamino)pyridine (DMAP). N‐(4‐Pyridinyl)piperazine as reactive group can be linked onto the macroporous polymeric carrier producing a polymer‐bound catalyst. A linear epoxy polymer containing the supernucleophilic functional groups have been synthesized by reaction of epichlorohydrin and 4‐aminopyridine. The linear polymeric catalysts have been braced by the macroporous resin to obtain a polymer‐supported linear polymeric catalyst. It is found that catalytic activity of bis‐DMAP approaches that of DMAP. The activity of the polymer‐supported linear polymeric catalyst is higher than that of the polymer‐bound catalyst in the acetylation of tert‐butyl alcohol, as monitored by gas–liquid chromatography. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 593–597, 2000     

芳烃绿色硝化催化剂的研究进展

硝硫混酸硝化法无位置选择性,副反应多,原子经济性差,存在设备腐蚀和环境污染等问题。开发绿色催化剂替代浓H2SO4,实现芳烃选择性硝化成为该领域的研究热点。本文综述金属盐、金属氧化物、固体酸、离子液体等催化剂催化芳烃绿色硝化的研究进展,分析其特点、催化机理及存在问题,并展望清洁硝化的研究方向。     

固体超强酸ZrO_2/SO_4~(2-)催化芳烃硝化性能研究

以固体超强酸ZrO2/SO42-为催化剂,苯和硝酸为原料合成硝基苯。最佳反应条件为:催化剂活化温度650℃,苯39.1 g,硝酸与苯摩尔比2.0,催化剂用量1.0 g,反应时间7 h,反应温度75℃,收率达78.3%。     

硝化法制备对氨基间硝基苯磺酸的研究

以对氨基苯磺酸为起始原料 ,经过乙酰化、硝化、水解三步来制备标题物。通过正交试验找出了酰化的最佳反应条件为 :对氨基苯磺酸与乙酐的摩尔比为 1∶1.0 5 ,反应总时间为 1.5h ,反应温度为 2 5℃ ,酰化介质为酰化反应前用碳酸钠及水将对氨基苯磺酸完全溶解 ,使混合液 pH值为 5～ 6 ,反应过程中不再补加碳酸钠 ,其酰化转化率可达 99.6 % ,酰化产物的固体收率可达 96 .0 % ;硝化反应的最佳条件为 :硝化剂用 90 .2 %的硝酸 ,对乙酰氨基苯磺酸与硝化剂的摩尔比为 1∶1.0 5 ,反应温度为 10℃ ,浓硫酸与对乙酰氨基苯磺酸的摩尔比为 8.3∶1,其硝化转化率可达 96 .0 % ,硝化反应的选择性好 ,对氨基邻硝基苯磺酸的量不到 1.0 %。     

On the acidity of liquid and solid acid catalysts. Part 2. A thermodynamic and kinetic study for acid-catalysed nitrations

Solid acids prepared by adding sulfuric acid on silica gel have been used as catalysts in the nitration of nitrobenzenes and their properties have been tested by kinetic studies at 25°C. Nitration rates in concentrated aqueous solutions of sulfuric acid were also analysed and the catalytic efficiencies of sulfuric acid in liquid and solid phase were compared by using kinetic data of analogous compounds. The results show that the solid acid samples exhibit nitrating properties very similar to those observed in concentrated aqueous solutions of sulfuric acid (range of 90 wt%). The relationship between nitration rates and effective concentration of electrophilic species [NO ₂ ⁺ ], determined by studying the protonation–dehydration equilibrium of nitric acid in strong acids (HNO₃ + H⁺ ⇌ H₂O + NO ₂ ⁺ ), was tested to better understand the acidity properties of medium. This revised version was published online in November 2006 with corrections to the Cover Date.     

Selective reduction of aromatic nitro compounds over recyclable hollow fiber membrane‐supported Au nanoparticles

Guanidylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (GPPO) hollow fiber membrane (HFM) supported Au nanoparticles are prepared by a simple adsorption‐reduction of Au³⁺ with sodium borohydride as a reducing agent and polyvinyl pyrrolidone as a dispersant. The novel heterogeneous catalyst shows high catalytic activity for the reduction of various aromatic nitro compounds in an aqueous medium at room temperature and can be easily reused for several runs, for example, for the reduction of nitrobenzene, the yield reaches up to 92% even after 10 cycles, indicating the potential application of GPPO HFM as a catalysts support material for sustainable chemistry. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41268     

Using a polymer‐supported azide ion in [2+3] cycloaddition reaction of azide ion with nitriles

The [2+3] cycloaddition between various nitriles and crosslinked poly(4‐vinylpyridine) supported azide ion proceeds smoothly in the presence of ammonium bromide or ammonium chloride in N,N‐dimethyl formamide, to give the corresponding 5‐substituted‐1H‐tetrazoles in good to high yields. Conventional heating was used to promote reaction. It was found that using nitriles with electron‐withdrawing groups result in bout higher yields and lower reaction times. The present procedure offers advantages, such as shorter reaction time, and simple workup. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

膨润土上负载AlCl３固体酸催化剂的制备

以无水三氯化铝为原料,并以处理过的膨润土为载体,采用液固溶剂法制备固体酸催化剂。用载铝量为检验指标,通过单纯型搜索法寻优,探讨各种因素对载铝量的影响,并分析了主次因素。     

Polyacenaphthylene supported t-butyl chromates: a new class of solid phase oxidizing reagents

Copolymers of acenaphthylene with divinylbenzene were functionalized by incorporating t-butyl chromate groups, and the resulting polymeric reagents were used to oxidize alcohols to carbonyl compounds. Primary and secondary alcohols were oxidized to the corresponding carbonyl compounds in quantitative yields. The extent of oxidation was found to depend on the various reaction parameters including the temperature, nature of the solvent, concentration of the reagent functions, duration of the reaction and the presence of catalyst. © 1998 SCI.     

An efficient and regioselective thiocyanation of aromatic and heteroaromatic compounds using cross-linked poly (4-vinylpyridine)-supported thiocyanate as a versatile reagent and potassium peroxydisulfate as a strong oxidizing agent

A green and regioselective thiocyanation of aromatic and heteroaromatic compounds has been achieved via a simple protocol using cross-linked poly (4-vinylpyridine)-supported thiocyanate ion, [P₄-VP]SCN, as a versatile polymeric reagent and potassium persulfate as a strong oxidizing agent, under heterogeneous conditions.

Various indoles, phenol and aniline derivatives, and pyrroles were transformed into their corresponding aryl thiocyanates in high to excellent yields. This procedure offers advantages such as short reaction time, simple reaction work-up, and the polymeric reagents can be regenerated and reused for several times without significant loss of their activity.     

Preparation of polymer‐supported polyethylene glycol and phase‐transfer catalytic activity in benzoate synthesis

The crosslinked polymeric microspheres (GMA/MMA) of glycyl methacrylate (GMA) and methyl methacrylate (MMA) were prepared by suspension polymerization. Polyethylene glycol (PEG) was grafted on GMA/MMA microsphers via the ring‐opening reaction of the epoxy groups on the surfaces of GMA/MMA microspheres, forming a polymer‐supported triphase catalyst, PEG‐GMA/MMA. The Phase‐transfer catalytic activity of PEG‐GMA/MMA microspheres was evaluated using the esterification reaction of n‐chlorobutane in organic phase and benzoic acid in water phase as a model system. The effects of various factors on the phase transfer catalysis reaction of liquid–solid–liquid were investigated. The experimental results show that the PEG‐GMA/MMA microspheres are an effective and stable triphase catalyst for the esterification reaction carried out between oil phase and water phase. The polarity of the organic solvent, the ratio of oil phase volume to water phase volume and the density of the grafted PEG on PEG‐GMA/MMA microspheres affect the reaction rate greatly. For this investigated system, the solvent with high polarity is appropriate, an adequate volume ratio of oil phase to water phase is 2:1, and the optimal PEG density on the polymeric microspheres is 15 g/100 g. Triphase catalysts offer many advantages associated with heterogeneous catalysts such as easy separation from the reaction mixture and reusability. The activity of PEG‐GMA/MMA microspheres is not nearly decreased after reusing of 10 recycles. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

蒙脱石负载铝基固体酸的制备及其催化性能

采用浸渍法制备了蒙脱石负载铝基固体酸(SO_4~(2-)/Al-O-MMT),用FTIR、XRD、TG/DSC、SEM、BET和PyFTIR对其结构进行表征与分析。以乙酸-正丁醇、柠檬酸-正丁醇的酯化反应为探针,研究了焙烧温度、浸渍液浓度对SO_4~(2-)/Al-O-MMT固体酸催化性能的影响,并测定SO_4~(2-)/Al-O-MMT固体酸的重复使用性。结果表明:蒙脱石负载铝基固体酸大大地提高了其催化活性。当焙烧温度为400℃,浸渍液浓度为0.75 mol/L时,SO_4~(2-)/Al-OMMT固体酸表现出最佳的催化活性,其催化合成乙酸正丁酯和柠檬酸三丁酯的酯化率分别可达到99.7%和96.1%。同时,SO_4~(2-)/Al-O-MMT固体酸表现出较好的重复使用稳定性,重复使用6次后,对于上述两个反应的酯化率分别保持在89.0%和84.6%。     

铌酸催化水解葡萄糖的研究

研究了铌酸催化水解葡萄糖溶液的反应,考察了不同热处理温度对铌酸催化剂活性的影响。研究发现,当热处理温度为400 ℃时,此类催化剂对葡萄糖催化水解生成乙酰丙酸（LA）的活性和选择性较好。对不同制备方法得到的铌酸催化剂活性进行比较,结果表明,直接水洗法制备得到的铌酸较有利于LA的生成。对用磷酸处理的铌酸催化剂进行考察发现,对于本反应体系,催化剂酸性的增加反而使活性下降。用XRD对催化剂的结构表征结果表明,催化剂活性与其表面是否结晶无明显关系。     

An assessment of biopolymer‐ and synthetic polymer‐based scaffolds for bone and vascular tissue engineering

The promise of tissue engineering is the combination of a scaffold with cells to initiate the regeneration of tissues or organs. Engineering of scaffolds is critical for success and tailoring of polymer properties is essential for their good performance. Many different materials of natural and synthetic origins have been investigated, but the challenge is to find those that have the right mix of mechanical performance, biodegradability and biocompatibility for biological applications. This article reviews key polymeric properties for bone and vascular scaffold eligibility with focus on biopolymers, synthetic polymers and their blends. The limitations of these polymeric systems and ways and means to improve scaffold performance specifically for bone and vascular tissue engineering are discussed. © 2013 Society of Chemical Industry     

Selective monochlorination of methane over solid acid and zeolite catalysts

Chlorination of methane was studied over amorphous silica-alumina, silicalite as well as H-mordenite, X, Y, NaL and H-ZSM-5 zeolite catalysts. The heterogeneous transformations were carried out in a continuous flow reactor in the 200–425 °C temperature range, under atmospheric pressure (methane to chlorine ratio 4:1, GHSV 600 ml/ g h). Chlorination of methane over zeolites in the 200–300 °C temperature range proceeds without selectivity indicating a radical mechanism. Above 300–350 °C, depending on the nature of zeolite, selective monochlorination takes place indicating the dominance of an ionic mechanism. H-mordenite was found to give the best monochlorination at the lowest temperature (99.2% CH₃Cl at 350 °C). The observed selectivity of the investigated zeolites is strongly time limited. All investigated catalysts lose their selectivity after five hours on-stream due to extraction of aluminum from the framework of zeolites by hydrogen chloride. Amorphous silica-alumina above 350 °C also catalyzes ionic chlorination. The chlorination of methane over silicalite proceeds via the nonselective radical pathway at the investigated temperatures.Catalysis by solid superacids, 28. For part 27, see ref. [1].     

固体酸催化蔗糖制备乙酰丙酸的研究

以蔗糖为原料,焙烧后的硫酸钛为催化剂,水为溶剂制备乙酰丙酸。研究了催化剂焙烧温度对催化剂活性的影响,以及催化剂投加量、蔗糖浓度、反应温度和反应时间对乙酰丙酸收率的影响。在反应温度220 ℃、反应时间60 min、蔗糖浓度50 g·L^-1和催化剂加入量0.5 g条件下,乙酰丙酸收率可达57.9%。