香茅基芳基醚类保幼激素类似物的简便合成方法

许多香叶基芳基醚和香茅基芳基醚已证明是有效的昆虫保幼激素^[1-3].以往合成此类化合物,只能在酚与较活泼的香叶基溴的反应中使用KOH(或NaOH),与较不活泼的香茅基溴的反应则仍沿用Williamson法.我们曾报导了以聚氧乙烯类表面活性剂代替冠醚作为相转移催化剂合成醚类化合物的方法^[4].     

Etherification of Phenols Catalysed by Solid-Liquid Phase Transfer Catalyst PEG400 without Solvent

Aromatic ethers were synthesised in excellent yields(above 86 %) and purity by the etherification of phenols with dimethyl sulfate or alkyl halides, catalysed by phase transfer catalyst PEG400 under solvent-free conditions, and the effects of some key reaction conditions were also studied.     

9,10-蒽醌-2-磺酰氯用于液相柱前相转移衍生测定水中酚的评价(英文)

 一种新的衍生试剂9,10 蒽醌 2 磺酰氯(ASC)首次用于酚类衍生。几种不同极性的酚被用于评价该试剂。为便于考察ASC对酚衍生的机理及优化衍生条件,制备了不同酚的标准衍生物并对它们进行了结构确证。衍生过程涉及去质子酚与特丁基铵阴离子形成离子对后被有机溶剂提取。衍生反应可以在室温下3min内在两相界面上定量完成。衍生产物很稳定,可以分别被正相和反相分离(相应地在320nm或256nm波长处检测),其浓度和响应在0 2μmol/L～200μmol/L内存在很好的线性关系。     

Phase Transfer Catalyzed Synthesis of Amides and Esters of 2,4-Dichlorophenoxyacetic Acid

A convenient procedure is reported for the preparation of amides and esters via the reaction of 2,4-dichlorophenoxyacetyl chloride with amines or phenols under the condition of liquid-liquid phase transfer catalysis using polyethylene gtycol-600 as the catalyst. The products have been characterised on the basis of analytical and spectral (IR and H-NMR) data.     

Mass spectrometric detection of the Gibbs reaction for phenol analysis

This paper describes a new method for detecting phenols, by reaction with Gibbs reagent to form indophenols, followed by mass spectrometric detection. Unlike the standard Gibbs reaction, which uses a colorometric approach, the use of mass spectrometry allows for simultaneous detection of differently substituted phenols. The procedure is demonstrated to work for a large variety of phenols without para‐substitution. With para‐substituted phenols, Gibbs products are still often observed, but the specific product depends on the substituent. For para groups with high electronegativity, such as methoxy or halogens, the reaction proceeds by displacement of the substituent. For groups with lower electronegativity, such as amino or alkyl groups, Gibbs products are observed that retain the substituent, indicating that the reaction occurs at the ortho or meta position. In mixtures of phenols, the relative intensities of the Gibbs products are proportional to the relative concentrations, and concentrations as low as 1 μmol/L can be detected. The method is applied to the qualitative analysis of commercial liquid smoke, and it is found that hickory and mesquite flavors have significantly different phenolic composition.     

Evaluation of a new reagent: anthraquinone-2-sulfonyl chloride for the determination of phenol in water by liquid chromatography using precolumn phase-transfer catalyzed derivatization

A new reagent, anthraquinone-2-sulfonyl chloride, is used for the derivatizaton of phenols. Several compounds with different polarities are selected to evaluate the new reagent and derivatives of these phenols that are prepared via a facile pathway. The optimal conditions for analytical derivatization and mechanism of the derivatization reaction are discussed. The derivatization procedure involves an ion-pair extraction of the deprotonated phenols with a tetrabutylammonium counter ion in the organic phase. At the interface of two phases, the derivatization reaction occurs quantitatively at room temperature within 3 min. The derivatives are stable and readily amenable to analysis by normal-phase (NP) and reversed-phase (RP) high-performance liquid chromatography (HPLC). Excellent linearity response was demonstrated over the concentration range of 0.2-200 micromol/L at 320 nm for NP-HPLC and at 256 nm for RP-HPLC. Combined with preconcentration using a Waters Sep-Pak Plus C(18) cartridge, detection limits of phenols for water-sample analysis are as low as 1 x 10(-9) mol/L (approximately 0.1 microg/mL).     

Synthesis of Polyfunctional Aromatic Ring Systems (Phloroglucide Analogs) under Microwave Irradiation

An efficient and rapid synthesis of phloroglucide analogs under microwave irradiation is described. The solid‐phase condensation reaction of the 4‐halo‐2,6‐bis(hydroxymethyl)phenols 1a , b with other substituted phenols in the presence of ZnCl₂ afforded the target molecules in much higher yields than by classical solution‐phase synthesis and allowed us to prepare new phloroglucide analogs possessing sensitive functional groups difficult to access by established means.     

液-液相转移催化法合成羧基苯氧基乙酸衍生物的研究

用液-液相转移催化法合成了19个羰芳氧基苯氧基乙酸芳酯和19种羰芳胺基苯氧基乙酰芳胺,并初步考查这些化合物对小麦生长的促进作用。     

Phase Transfer Catalyzed Synthesis of Diaryl 1,4—Phenylene Dioxydiacetate

The title compounds 3a—3o were prepared with high yield via the reaction of 1, 4-phenylenedioxydiacetyl chloride with various substituted phenols under the condition of liquid-liquid phase transfer catalysis, using polyethylene glycol—400 as the catalyst.     

Dehydrative C-H alkylation and alkenylation of phenols with alcohols: expedient synthesis for substituted phenols and benzofurans

A well-defined cationic Ru-H complex catalyzes the dehydrative C-H alkylation reaction of phenols with alcohols to form ortho-substituted phenol products. Benzofuran derivatives are efficiently synthesized from the dehydrative C-H alkenylation and annulation reaction of phenols with 1,2-diols. The catalytic C-H coupling method employs cheaply available phenols and alcohols, exhibits a broad substrate scope, tolerates carbonyl and amine functional groups, and liberates water as the only byproduct.     

N-Picolinamides as ligands in Ullman type C–O coupling reactions

Copper-catalyzed modified Ullmann coupling reactions creating C–O bonds, including diaryl ethers or phenols, are vital to organic synthesis. Synthesized N-phenyl-2-pyridinecarboxamide and its derivatives were used as ligands in conjunction with catalytic copper sources in the formation of various diaryl ethers and phenols. Various aryl and heteroaryl halides with electron donating and withdrawing groups were reacted with various phenols under mild reaction conditions providing moderate to excellent yields.     

Reactivity of ozone as a hydrogen-atom acceptor in reactions with antioxidants

Atom abstraction is shown to be the main reaction of ozone with phenols, aromatic amines and hydroxylamines in non-polar solvents. These reactions were analysed by using the parabolic model of the transition state of free-radical reactions. Activation energies and rate constants of ozone reactions with 144 phenols, sterically hindered phenols, aromatic amines and hydroxylamines were calculated. The results are in agreement with experimental measurements. The mechanism of ozone reaction with antioxidants is discussed.     

Solid‐Phase Organic Synthesis of Aryl Vinyl Ethers Using Sulfone‐Linking Strategy

A novel facile solid‐phase organic synthesis of aryl vinyl ethers by reaction of polystyrene‐supported 2‐phenylsulfonylethanol with phenols under Mitsunobu conditions and subsequent elimination reaction with DBU has been developed. The advantages of this method include straightforward operation, good yield and high purity of the products. Alternatively, a typical example of Suzuki coupling reaction on‐resin was further applied to prepare 4‐phenylphenyl vinyl ether for extending this method.     

一水硫酸氢钠无溶剂催化合成4-甲基香豆素

NaHSO4•H2O(摩尔分数为0.1)催化下, 取代酚与乙酰乙酸乙酯(物质的量比1∶1.2)在无溶剂条件下, 通过Pechmann缩合反应, 合成了9个4-甲基香豆素衍生物, 反应时间3～5 h, 产率23%～91%, 反应条件温和、操作简便有效. 研究结果表明, 当苯酚环上取代基为一个羟基或氨基能显著加速反应, 提高产率, 苯环上更多的取代基则对反应没有促进作用; 当苯酚环上取代基为吸电子基团时, 则不发生反应或者产率很低.     

Ullmann diaryl ether synthesis: rate acceleration by 2,2,6,6-tetramethylheptane-3,5-dione

[reaction: see text]. In the copper salt catalyzed ether formation from aryl bromides or iodides and phenols, 2,2,6,6-tetramethylheptane-3,5-dione (TMHD) was found to greatly accelerate the ordinarily difficult reaction, making it occur under more moderate temperatures and reaction times. A series of aryl halides and phenols were shown to form ethers in NMP as the solvent, cesium carbonate as the base, and CuCl and TMHD as the catalysts. The reaction was shown to tolerate electron-rich aryl bromides and electron-neutral phenols.     

Use of sonication for the coupling of sterically hindered substrates in the phenolic Mitsunobu reaction

A vast rate increase in the Mitsunobu reaction of phenols with alcohols where either or both are sterically hindered has been achieved by the use of high concentration combined with sonication.     

Chitosan-coated electrodes for bimodal sensing: selective post-electrode film reaction for spectroelectrochemical analysis

Electrochemical methods are well suited for chemical detection in hand-held devices because they are simple, fast, and sensitive. However, electrochemical detection methods generally suffer from limitations in selectivity. We report a novel approach that enables electrochemically initiated reactions to generate optical signals that can be used to enhance the discriminating power for the electrochemical analysis of antioxidant food phenols. This spectroelectrochemical approach employs transparent electrodes coated with a film of the aminopolysaccharide chitosan. The phenolic analytes diffuse through the chitosan film to the electrode where they are anodically oxidized into electrophilic intermediates that undergo postelectrode reactions with the chitosan film. The postelectrode reaction was analyzed by FTIR and XPS, and this reaction was observed to impart optical properties (color and UV-visible absorbance) to the otherwise colorless and transparent chitosan film. We demonstrate that the optical signal generated from the postelectrode film reaction is selective for oxidized phenols, compared to that for unoxidized phenols or the nonphenolic antioxidant ascorbic acid. Furthermore, we demonstrate that the optical signal (film absorbance) can be correlated to the electrical signal (charge transferred). Finally, we use simple mixtures to demonstrate that the coupling of information from independent optical and electrical measurement modes can assist in the qualitative analysis of antioxidant phenols. Potentially, the postelectrode film reaction may provide a selective and reagentless alternative to conventional colorimetric methods for detecting antioxidant phenols. In a broader perspective, this work suggests the potential for coupling independent detection modes (optical and electrical) to enhance the information content of sensor measurements.     

Direct synthesis of phenols by iron-catalyzed biphasic oxidation of aromatic hydrocarbons with hydrogen peroxide

The hydroxylation of a series of aromatic hydrocarbons with hydrogen peroxide, catalyzed by iron complexes with pyrazine-3-carboxylic acid N-oxide, was investigated, operating in a biphasic reaction medium.

The new catalyst showed a high selectivity to the corresponding phenols, minimizing the over-oxidation reactions to polyoxygenated derivatives and tars which, along with dimers formation, are the major limitations of the classical Fenton’s reagent for a practical synthetic application.

In the case of alkylbenzenes, the competitive side chain oxidation at the benzylic positions also occurred. Electron rich substrates, such as anisole, were oxidized with very poor selectivity.

The reactions were carried out in a biphasic system that allows a convenient recovery and recycling of the catalyst by phase separation techniques. The catalyst showed a complete retention of activity after six consecutive reaction cycles.

The new catalyst appears as a promising tool for the direct synthesis of phenols, in alternative to the conventional multi-step methods.     

Synthesis of poly(vinylbenzyltriphenylphosphonium)-bound nucleophilic reagents and their applications for anionic activation in nucleophilic substitutions

Insoluble polymer-bound nucleophilic reagents derived from poly(vinylbenzyltriphenylphosphonium chloride) have been prepared by treatment with the sodium salts of carboxylic acids, benzenesulphinic acid and phenols. These reagents were used for the synthesis of carboxylic acid esters, sulphones and C/O-alkylation of phenols by reactions with alkyl halides. In addition to the ease and simplicity of the method and regeneration of the polymeric by-product, the polymeric reagent seems to increase the nucleophilicity of the anions. The products were obtained in higher yields than those for the corresponding polymeric phase transfer catalyst which need long reaction time and gave no satisfactory yields especially in non-polar solvents.     

Zirconia-Modified Superacid UDCaT-5: An Efficient and Versatile Catalyst for Alkylation Reactions under Solvent-Free Conditions

UDCaT-5, a modified version of zirconia, efficiently catalyzes alkylation of phenols with alcohols under environmentally safe, heterogeneous reaction conditions with high selectivity and in excellent yields. The high content present in UDCaT-5 with preservation of tetragonal phase of zirconia was responsible for the superactivity. Several phenolic compounds carrying either electron-sulfer releasing or electron-withdrawing substituents in the ortho, meta, and para positions afforded high yields of the products.