Benzylation of thiophene using zinc and iron chloride modified montmorillinite clay

Montmorillinite clays, modified with either Zn(II) or Fe(III) chlorides have been used to catalyze the Friedel-Crafts alkylation of thiophene. High yields (ca. 80%) of 2- and 3-benzylthiophene mixtures were obtained using either catalyst in chlorobenzene or nitrobenzene solvent at 80°C. The ratio of 2–3-products was found to be controlled by their relative stability. Reactions were most rapid in nitrobenzene solution (<5 min) and resulted in formation of the 2-isomer as the only mono-substituted product. This is believed to be the first example in which an alkylation of thiophene has been limited to one regio-isomer.     

2-苄基-4-氯苯酚的合成工艺

以非极性溶剂环己烷为介质,以无水氯化锌为催化剂,氯化苄与对氯苯酚在温和条件下合成2-苄基-4-氯苯酚.研究了溶剂、催化剂、反应温度等因素对反应的影响,并对产品进行了表征.结果表明,使用非极性的环己烷为溶剂,对氯苯酚浓度20%,对氯苯酚与氯化苄物质的量比5∶1,无水氯化锌为氯化苄质量的10%,温度30 ℃下反应6 h,产品收率达到78.7%.     

ZnCl2/Si-MCM-41催化剂的制备、表征及催化性能研究

通过浸渍法制备了新型的环境友好催化剂ZnCl2／Si-MCM-41。考察了它在苯与苄氯的苄基化反应上的活性，探索了制备ZnCl2／Si-MCM-41负载试剂的最佳制备条件。研究表明：ZnCl2／Si-MCM-41的最佳制备条件是负载量为4mmol/g，活化温度为150℃，活化时间为5h。通过XRD、TG、FT-IR对催化剂进行表征，发现ZnCl2在较低负载量时，ZnCl2充分分散在载体孔道内，对催化剂载体的结构没有明显的影响，而且此负载试剂上苯的苄基化反应的活性中心不是晶体ZnCl2，而是存在于载体表面的非晶态ZnCl2物种。     

Mild synthesis of benzylated bamboo in LiCl/DMSO solution

Benzylated bamboo was mildly synthesized in nonaqueous medium without mercerization pretreatment. The ball-milled bamboo was firstly preswelled in lithium chloride/dimethyl sulfoxide (LiCl/DMSO) solution and then reacted with benzyl chloride in the presence of solid NaOH with varying molar ratios of benzyl chloride to OH groups of bamboo (1–4), reaction times (1–8 h), and temperatures (60–90°C). Benzylated bamboo products with yields from 51.1 to 106.9% and with degrees of substitution [DS, apparent value evaluated by Fourier transform infrared (FTIR) spectra] between 0.2 and 1.2 were synthesized. FTIR and ¹³C cross polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy confirmed the incorporation of benzyl groups into bamboo; SEM observations of the highly benzylated bamboo showed porous surface with small irregular slices ascribed to the disruption of intermolecular and intramolecular hydrogen bonds between cellulose. Because of the degradation of amorphous components, the crystallinity decreased negligibly after modification and the thermal stability increased slightly but was lower than that of cellulose. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Nickel‐Catalyzed Reductive Benzylation of Aldehydes with Benzyl Halides and Pseudohalides

The reductive benzylation of aromatic and aliphatic aldehydes with benzylic halides is reported using a nickel/zinc catalyst system. In addition to benzylic halides, the first report on the addition of benzylic triflates, acetates, tosylates and tritylates to aldehydes is also presented. By this new method a range of alcohols was synthesized efficiently from aldehydes and benzylic substrates at room temperature in moderate to high yields. The mild reaction conditions and good functional group tolerance make this nickel‐catalyzed process synthetically useful for the synthesis of diverse benzylic alcohols.

     

苄基化疏水改性淀粉的合成及水煤浆分散性能

采用氧化淀粉和羟乙基淀粉为原料,氯化苄为疏水剂,引入一定量的疏水基团苄基,制备出两种新型苄基化改性淀粉(氧化苄基化淀粉(OBS)和羟乙基苄基化淀粉(HBS))。将OBS和HBS作为分散剂应用于神华煤制备水煤浆,探讨改性淀粉对浆体的表观黏度、制浆浓度、稳定性和流变性的影响。结果表明:OBS和HBS的最佳添加量为0.50%(质量分数,下同),最大制浆浓度为65%;苄基化疏水改性后制得的淀粉分散剂均具有较好的分散效果,含苄基和羧基更多的OBS分散剂性能更佳,浆体表观黏度为842 mPa·s,7 d析水率为4.3%,煤颗粒表面Zeta电位降至-36.2 mV,体现出较好的稳定性和流变特性。OBS分散剂通过结构中的疏水基团苄基与煤中的硫水区域通过π电子极化作用力结合,形成平躺的线性折叠链式吸附。     

Direct Use of Benzylic Alcohols for Gold(III)‐Catalyzed S‐Benzylation of Mercaptobenzoic Acids in Water

We demonstrate the gold(III)‐catalyzed direct substitution of benzylic alcohols in water. These atom economic and environmentally benign protocols afford S‐benzylated products in moderate to excellent yields. In contrast, common Lewis or Brønsted acids as catalyst, and organic solvents such as dichloromethane or toluene were ineffective for the S‐benzylation of mercaptobenzoic acids. Water can be an attractive tool for new transition metal‐catalyzed reactions. A Hammett study for the rate constants with various substituted alcohols shows a good correlation (R²=0.97) between the log(k_X/k_H) and the σ⁺ value of the respective substituents. From the slope negative ρ values of 2.35 are obtained, suggesting that there is a build‐up of positive charge in the transition state. Our catalytic system can be performed with the use of only 2 mol% of gold(III) catalyst without any other additives in water, and scaled up to 10 mmol scale (85% isolated yield). Notably, the present method can accomplish the S‐benzylation of unprotected mercaptobenzoic acids, which is chemoselective and leaves the carboxyl group intact. Furthermore, the direct substitution of allylic and propargylic alcohols also proceeded smoothly in good yields.

     

Development of Fe‐, Sb‐, Bi‐ and Al‐impregnated silica catalysts using rice husk silica as a support for Friedel–Crafts benzylation of arenes

The milling by‐product of rice, rice husk, constitutes a major waste of the agricultural industry. It is mainly used as a fuel additive for various purposes, leaving behind residual ash which is rich in silica (Biogenic silica). In the present project, rice husk silica was impregnated with Fe³⁺, Sb³⁺, Bi³⁺ and Al³⁺ from both their aqueous and organic solutions. The resultant catalysts were activated at 120 °C and 550 °C and used for the Friedel–Crafts benzylation of benzene using benzyl chloride. Copyright © 2003 Society of Chemical Industry     

Palladium‐Catalyzed Selective C?H Benzylation towards Functionalized Azoles with a Quaternary Carbon Center

The direct C H benzylation of azoles with benzyl chlorides proceeds efficiently, via sequential cleavage of one sp² C H bond and two sp³ C H bonds in the presence of a palladium catalyst, to generate a wide range of tribenzylated azoles with a quaternary carbon center efficiently. The same catalyst could also promote the mono‐ and di‐benzylation reactions through fine turning of the base and reaction conditions.     

Al~(3+)改性膨润土催化剂在甲苯苄基化反应中的活性

以提纯膨润土为载体、AlCl3溶液为改性剂,制备了负载Al3+改性膨润土催化剂;采用氮吸附、XRD、FTIR、TG-DSC、SEM和NH3-TPD等手段表征了催化剂的微观结构;考察了Al3+负载量、焙烧温度、反应时间、反应温度和催化剂用量对负载Al3+改性膨润土催化氯苄与甲苯的苄基化反应的性能。表征结果显示,负载Al3+后膨润土表面酸活性中心显著增多,比表面积和孔体积显著增大,催化氯苄与甲苯的苄基化反应的活性很高。适宜的制备条件为:Al3+负载量0.4CEC(CEC为提纯膨润土的阳离子交换容量,为112 mmol(以100 g膨润土计)),焙烧温度200～400℃;适宜的反应条件为:反应温度120℃、反应时间不少于4 h、催化剂用量0.16 g/mL。