乙酸促进邻甲基苯磺酸铜选择性催化醇和酚的四氢吡喃化反应

室温无溶剂条件下, 乙酸能有效促进邻甲基苯磺酸铜催化一系列醇或酚和3,4-2H-二氢吡喃反应, 生成相应的四氢吡喃醚. 在乙酸存在条件下, 体系的催化性能有显著提高, 邻甲基苯磺酸铜用量仅需0.3 mol%(占醇或酚的摩尔分数)就能使反应在较短时间内完成. 反应结束后, 邻甲基苯磺酸铜经简单相分离可多次重复使用, 催化活性无明显下降. 产物结构经IR, 1H NMR, 元素分析进行表征.     

Copper(I)‐catalyzed multicomponent reactions in sustainable media

Multicomponent reactions including Biginelli reaction and A³ coupling are useful synthetic methodologies as they can provide valuable intermediates and building blocks for the synthesis of bioactive natural compounds. The heterocyclic products of these transformations represent antibacterial, antitumor or anti‐inflammatory properties. In presented study, copper‐mediated protocols for Biginelli reaction and A³ coupling in sustainable solvents were reported. At first, charged NHC copper complexes were synthesized in few steps and characterized using spectroscopic methods followed by preliminary activity tests in sustainable media. Later in this study, Biginelli reaction and A³ coupling were proceeded using prepared copper catalytic systems under mild conditions. Desired nitrogen‐bearing products were obtained with moderate to very high yields. Some attempts to recycle one of the received NHC copper initiators were also investigated.     

Catalytic asymmetric Henry reactions of silyl nitronates with aldehydes

A catalytic enantioselective Henry reaction of silyl nitronates with aldehydes has been developed. Different chiral Lewis acids have been tested for the reaction and it has been found that a variety of chiral copper-ligand complexes can catalyze the Henry reaction. The best yield, diastereo- and enantioselectivity of the nitroalcohols formed are obtained by the application of a copper(II)-diphenyl-bisoxazoline complex as the catalyst in the presence of tetrabutylammonium triphenylsilyldifluorosilicate (TBAT). In order to minimize the epimerization of the nitroaldol products they were converted into the corresponding Mosher esters. The reaction proceeds well for different aromatic aldehydes reacting with alkyl nitronates.     

高Cu含量MCM-41在苯直接羟基化反应中的催化性能

 考察了高铜含量(最高达26.0%)且铜原子主要处于中孔骨架的Cu-MCM-41在苯/过氧化氢直接羟基化制备苯酚反应中的催化性能,研究了铜含量、催化剂用量、溶剂种类、反应物摩尔比、温度以及时间等对催化剂活性的影响. 结果表明,该催化剂在苯直接羟基化反应中具有良好的催化活性,在最佳反应条件下,可使苯转化率达52.9%, 苯酚选择性达58.9%, 苯酚收率达31.2%, 优于文献报道的低铜含量中孔分子筛的催化结果. 另外,从反应机理对影响反应的因素进行了初步探讨.     

Rapid and cleaner synthesis of 1,4‐dihydropyridines in aqueous medium

The present investigation deals with a novel water soluble Lewis acid complex, Zn[(L)proline]₂ catalyzed Hantzsch 1,4‐dihydropyridine derivatives syntheses in aqueous medium assisted by microwave irradiation. The microwave promoted syntheses in aqueous medium afforded moderate to excellent yield (up to 98%) within short reaction time and allowed the reaction to take place with low microwave power (200 W). This synthetic methodology provides easier separation of products and the catalyst exhibits recycling ability without loss of its catalytic activity up to five reaction cycles. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:267–271, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20197     

Catalytic Asymmetric Conjugate Addition of a Borylalkyl Copper Complex for Chiral Organoboronate Synthesis

We report the catalytic enantioselective conjugate addition of a borylalkyl copper nucleophile generated in situ from a 1,1‐diborylmethane derivative to α,β‐unsaturated diesters. In the presence of a chiral N‐heterocyclic carbene (NHC)–copper catalyst, this method facilitated the enantioselective incorporation of a CH₂Bpin moiety at the β‐position of the diesters to yield β‐chiral alkyl boronates in up to 86 % yield with high enantioselectivity. The alkylboron moiety in the resulting chiral diester products was converted into various functional groups by organic transformation of the C?B bond.     

Chemoselective nucleophilic fluorination induced by selective solvation of the SN2 transition state

Reaction of the fluoride ion with secondary alkyl halides leads to 90% of elimination reaction and only 10% of nucleophilic substitution in dipolar aprotic solvents. Adding water to the organic phase, the SN2 yield increases in the cost of decreased reactivity. Using ab initio calculations, we have shown that it is possible to increase the reaction rate and the selectivity toward the SN2 process through supramolecular organocatalysis. The catalytic concept is based on selective solvation of the transition state through two hydrogen bonds provided by the 1,4-benzenedimethanol. The two hydrogen bonds between the catalyst and the SN2 transition state favor this pathway while just one strong hydrogen bond between the catalyst and the fluoride ion leads to a lower stabilization of the nucleophile, resulting in a higher reaction rate. Our calculations predict that the substitution product increases to 40% yield because of the selective catalysis provided by the 1,4-benzenedimethanol.     

Microwave-assisted expeditious hydrolysis of isobenzofuranone derivatives using silica supported acid under organic solvent-free conditions

Silica sulfuric acid was found to be an efficient, reusable and environment-friendly catalyst for fast hydrolysis of various isobenzofuranone to corresponding 2-ketomethylquinoline derivatives in a high yield under solvent-free using microwave irradiation. As the activator of silica sulfuric acid the wet SiO₂ was chosen. The reactions in conventional conditions were compared with the microwave assisted reactions. This approach can prove beneficial since the recovery of solvents from conventional reaction systems always results in some losses.     

Microwave‐assisted suzuki coupling reaction for rapid synthesis of conjugated polymer–poly(9,9‐dihexylfluorene)s as an example

Long reaction period (dozens of hours) is often required for the synthesis of conjugated polymers by palladium‐catalyzed Suzuki polymerization reaction. This work shows that microwave can accelerate Suzuki polymerization to realize the ultra‐rapid synthesis of conjugated polymers, here poly(9,9‐dihexylfluorene)s (PDHFs) as an example. The effects of reaction conditions on the polymerization have been systematically investigated, including the mode of microwave irradiation, microwave power, reaction temperature, reaction time, solvents, catalyst species, and catalyst concentrations. Compared with the conventional heating method (oil bath) for the synthesis of PDHFs (48 h, M_w = 20,000 g/mol), Suzuki polymerization under optimized microwave condition can yield PDHFs with higher molecular weight (M_w = 40,000 g/mol) in a much shorter time (14 min). The structures of obtained PDHFs samples are fully characterized spectroscopically, demonstrating well‐defined PDHFs have been prepared through microwave‐assisted (MA) Suzuki polymerization reaction. In addition, the mechanism of MA Suzuki polymerization is proposed preliminarily. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Solvent-free,scalable and expeditious synthesis of benzanilides under microwave irradiation using clay doped with palladium nanoparticles as a recyclable and efficient catalyst

Benzanilide synthesis through amide bond formation was effectively carried out by palladium-doped clay catalyst using microwave irradiation under solvent-free conditions. Products were obtained with excellent yield in very short reaction time and only a small amount of the catalyst was used. The catalyst could be separated easily and recycled several times with insignificant loss in catalytic activity. No column purification was required and the products were purified by the crystallization method. The heterogeneous character of the catalyst in a ligand-free, solvent-free and base-free system supports for a practical and environmentally benign process.     

微波协同强酸性大孔树脂催化合成肉桂酸正丙酯的研究

研究了微波辐射强酸性大孔树脂催化合成肉桂酸正丙酯的合成工艺.通过优化合成工艺得到了最佳工艺条件,肉桂酸0.01mol,酸醇摩尔比1:5,催化剂为CAT 600树脂,催化剂用量为反应物质量的30%,微波功率400W,反应时间30min,产率达93.68%.催化剂可再生循环使用,催化性能稳定.     

Aromatics and phenols from catalytic pyrolysis of Douglas fir pellets in microwave with ZSM-5 as a catalyst

Microwave assisted catalytic pyrolysis was investigated to convert Douglas fir pellets to bio-oils by a ZSM-5 zeolite catalyst. A central composite experimental design (CCD) was used to optimize the catalytic pyrolysis process. The effects of reaction time, temperature and catalyst to biomass ratio on the bio-oil, syngas, and biochar yields were determined. GC/MS analysis results showed that the bio-oil contained a series of important and useful chemical compounds. Phenols, guaiacols, and aromatic hydrocarbons were the most abundant compounds which were about 50–82% in bio-oil depending on the pyrolysis conditions. Comparison between the bio-oils from microwave pyrolysis with and without catalyst showed that the catalyst increased the content of aromatic hydrocarbons and phenols. A reaction pathway was proposed for microwave assisted catalyst pyrolysis of Douglas fir pellets.     

Ring-closing metathesis in glycerol under microwave activation

Glycerol, a biodegradable and virtually non-toxic bio-sourced chemical can be used as an alternative, reusable, sustainable solvent, with so far limited application in the field of green organic chemistry. Herein, the reaction conditions have been screened for the ring-closing metathesis (RCM) of N,N-diallyltosylamine and diethyl diallylmalonate in glycerol, under microwave irradiation and in the presence of the most common commercially available RCM catalysts. The products were isolated in high yield after extraction and the catalyst could be recycled up to two times. Results with simultaneous cooling of the reaction vessel under microwave irradiation are also reported.     

微波辅助催化氧化苯高性能催化剂实验研究

采用传统浸渍法制备分子筛负载过渡金属和稀土元素催化剂,通过微波辅助催化氧化苯性能实验考察其催化活性。研究表明,天津科密欧的5A分子筛为优良的催化剂载体,分子筛负载铜-锰-铈催化剂对苯的完全燃烧温度为230℃,铜(Cu)锰(Mn)双金属催化剂中晶相与非晶相Cu_1.5Mn_1.5O₄尖晶石提高了催化剂的催化活性,稀土铈(Ce)的助催化效果显著;30 h的连续性实验表明,Cu-Mn-Ce/分子筛催化剂具有良好的稳定性和高的催化活性。催化剂的比表面积和表面形貌表征表明,催化剂比表面积和孔径受高温煅烧和氧化反应而增大,从而有助于苯的吸附与氧化降解;X射线衍射表明,实验前后分子筛结构未发生明显变化,铜锰主要以二价和三价的氧化物形态分布于催化剂表面。     

Iron‐catalyzed cross‐coupling reaction: Heterogeneous palladium and copper‐free Heck and Sonogashira cross‐coupling reactions catalyzed by a reusable Fe(III) complex

An interesting silica‐supported iron catalyst was successfully prepared and demonstrated as an efficient heterogeneous catalyst for cross‐coupling reactions of aryl halides. The as‐prepared nanocatalyst was well characterized and found to be highly efficient in Heck reaction under mild and sustainable conditions (water as solvent at 80 °C in short reaction time). Furthermore, the obtained catalyst was used as an efficient, inexpensive and green heterogeneous catalyst for Sonogashira cross‐coupling reactions of various aryl iodides and provided the corresponding products with moderate to good yields. This phosphine, copper and palladium‐free catalyst was simply recovered from the reaction mixture and recycled five times without substantial decrease in its catalytic activity.     

An efficient synthesis of tertiary amines from nitriles in aprotic solvents

Tertiary amines are utilized extensively as non-nucleophilic proton scavengers for a number of organic transformations. Herein we report the efficient syntheses of tertiary alkyl amines from their corresponding alkyl nitriles in the presence of a heterogeneous palladium catalyst and a source of dihydrogen in aprotic solvents. The reaction is atom economic, the conditions are mild, and the isolated yields are virtually quantitative. The degree of amine alkylation shows some solvent dependency; in polar protic solvents such as ethanol or methanol, the reaction affords a mixture of products with the secondary alkyl amine as the major product.     

Mild Copper‐Catalyzed Fluorination of Alkyl Triflates with Potassium Fluoride

A chemoselective catalytic fluorination of alkyl triflates is described using potassium fluoride as a fluoride source. Excellent yields of the desired alkyl fluorides are obtained after one hour at 45 °C using 2 mol % of the copper catalyst. With 10 mol % of the catalyst, full conversion can be achieved in less than 10 minutes at 45 °C, and thus makes this procedure potentially suited for the preparation of ¹⁸F‐labeled PET probes. As a result of the mild reaction conditions, only the substitution products are observed with no evidence of common side reactions, such as elimination. Reported is a preliminary study of the reaction scope, which demonstrates that the fluorination can be performed in the presence of a wide range of functional groups. Evidence suggests an unusual role of the [IPrCuOTf] catalyst as a phase‐transfer catalyst and points to [IPrCuF] as the active fluorinating reagent (IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene).     

Rapid and efficient one-pot synthesis of octahydroquinazolinone derivatives using lanthanum oxide under solvent-free condition

A simple, efficient and cost-effective method for the synthesis of octahydroquinazolinone derivatives using dimedone, urea/thiourea and aromatic aldehydes using lanthanum oxide as a catalyst under solvent free condition in microwave irradiation is reported. The present method does not involve any hazardous organic solvents. This catalyst has promising features for the reaction response such as the shortest reaction time, excellent product yields, simple work-up procedure and purification of products by non-chromatographic methods.     

Copper‐Catalyzed Coupling of Triaryl‐ and Trialkylindium Reagents with Aryl Iodides and Bromides through Consecutive Transmetalations

An efficient copper(I)‐catalyzed coupling of triaryl and trialkylindium reagents with aryl iodides and bromides is reported. The reaction proceeds at low catalyst loadings (2 mol %) and generally only requires 0.33 equivalents of the triorganoindium reagent with respect to the aryl halide as all three organic nucleophilic moieties of the reagent are transferred to the products through consecutive transmetalations. The reaction tolerates a variety of functional groups and sterically hindered substrates. Furthermore, preliminary mechanistic studies that entailed the synthesis and characterization of potential reaction intermediates offered a glimpse of the elementary steps that constitute the catalytic cycle.     

Cu(II) 2-quinoxalinol salen catalyzed oxidation of propargylic,benzylic, and allylic alcohols using tert-butyl hydroperoxide in aqueous solutions

The synthesis of carbonyl compounds by oxidation of alcohols is a key reaction in organic synthesis. Such oxidations are typically conducted using catalysts featuring toxic metals and hazardous organic solvents. Considering green and sustainable chemistry, a copper(II) complex of sulfonated 2-quinoxalinol salen (sulfosalqu) has been characterized as an efficient catalyst for the selective oxidation of propargylic, benzylic, and allylic alcohols to the corresponding carbonyl compounds in water when in combination with the oxidant tert-butyl hydroperoxide. The reactions proceed under mild conditions (70 °C in water) to produce yields up to 99% with only 1 mol % of catalyst loading. This reaction constitutes of a rare example of propargylic alcohol oxidation in water, and it makes this process greener by eliminating the use of hazardous organic solvents. Excellent selectivity was achieved with this catalytic protocol for the oxidation of propargylic, benzylic, and allylic alcohols over aliphatic alcohols. The alcohol oxidation is thought to go through a radical pathway.