Heck reactions of aryl bromides with alk-1-en-3-ol derivatives catalysed by a tetraphosphine/palladium complex

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ efficiently catalyses the Heck reaction of alk-1-en-3-ol with a variety of aryl bromides. In the presence of hex-1-en-3-ol or oct-1-en-3-ol, the β-arylated carbonyl compounds were selectively obtained. Linalool and 2-methylbut-3-en-2-ol led to the corresponding 1-arylalk-1-en-3-ol derivatives. Turnover numbers up to 69,000 can be obtained for this reaction. A minor electronic effect of the substituents of the aryl bromide was observed. Similar reaction rates were observed in the presence of activated aryl bromides such as bromoacetophenone and deactivated aryl bromides such as bromoanisole.     

Cross-coupling reactions of (1-fluorovinyl)methydiphenylsilane(1) with aryl halides and aryl triflates

The cesium fluoride (CsF)-assisted cross-coupling reaction of (1-fluorovinyl)methyldiphenylsilane (1) with aryl halides and aryl triflates was examined. The reaction with aryl iodides smoothly proceeded to afford the corresponding (1-fluorovinyl)arenes in the presence of a catalytic amount of CuI and Pd(PPh(3))(4) in aprotic polar solvents such as DMF, DMI, DMA, and NMP in good yields. A variety of functional groups (nitro, ester, ketone, and ether) on the aromatic rings can be tolerated under these mild conditions. Aryl iodides are superior to aryl bromides as the coupling reaction partner. The cross-coupling reaction of 1 with aryl triflates instead of aryl halides was also accomplished in the presence of tetrabutylammonium iodide (n-Bu(4)NI) as the additive under similar conditions.     

Amino acids as selective acylating agents: regioselective N-acylation of imidazolidin-4-one derivatives of the antimalarial drug primaquine

The acylation of bioactive primaquine-based imidazolidin-4-ones was studied using N^α-Boc-protected glycine as acylating agent. Two synthesis routes, eight different coupling methods and seven distinct solvents were compared. Mild carbodiimide-based couplings on high dielectric constant solvents such as DMF or MeCN increased acylation yields, whereas alcohols inhibited carbodiimide-mediated acylations to take place. Achievement of the synthetic goals was limited by the size of the imidazolidin-4-one ring substituents R¹, R² and R³, but resort to MW-assisted synthesis allowed overcoming such obstacle, though with very modest reaction yields. All reactions involving a Boc-protected amino acid were regioselective, independent of reaction conditions employed. In contrast, regioselective acetylation of the imidazolidin-4-ones could only be achieved by resort to very mild coupling procedures.     

Selective Heck reaction of aryl bromides with cyclopent-2-en-1-one or cyclohex-2-en-1-one

The selective Heck reaction of cyclopent-2-en-1-one or cyclohex-2-en-1-one with aryl bromides gives a simple access to the corresponding 3-arylcycloalk-2-en-1-ones. The choice of the base was found to be crucial to avoid the formation of 3-arylcyclopentanones or 3-arylcyclohexanones as side-products. Using KF as base, DMF as solvent and Pd(OAc)₂ as catalyst, the target products were obtained in moderate to good yields with a variety of aryl bromides. Substituents such as fluoro, trifluoromethyl, acetyl, benzoyl, formyl, ester or nitrile on the aryl bromide are tolerated. Sterically congested aryl bromides or bromopyridines can also be employed.     

Palladium-catalysed direct arylations of NH-free pyrrole and N-tosylpyrrole with aryl bromides

The palladium-catalysed direct coupling of aryl halides with pyrroles provides a greener access to arylated pyrroles than more classical couplings such as Suzuki, Stille or Negishi reactions. However, so far, NH-free pyrrole and N-tosylpyrrole gave disappointing results for such couplings either in terms of regioselectivity of the arylation, catalyst loading or substrate scope. The reactivity of both NH-free pyrrole and N-tosylpyrrole was studied, and the tosylated pyrrole led to higher yields of coupling products due to better conversions of the aryl bromides. A range of aryl bromides undergo regioselective coupling at C2 of N-tosylpyrrole in moderate to good yields using 1 mol % [Pd(Cl(C₃H₅)]₂ as the catalyst, KOAc as the base in DMAc.     

Novel fluorinated poly(aryl ether)s derived from 1,2-bis(4-(4-fluorobenzoyl)phenoxy)-hexafluorocyclobutane

Two novel poly(aryl ether)s were prepared from 1,2-bis(4-(4-fluorobenzoyl)-phenoxy)-hexafluorocyclobutane and aromatic bisphenols by the aromatic nucleophilic substitution reaction in a polar aprotic solvent. These polymers have good thermal stability up to 341 °C with 10% weight loss in inert atmosphere and good solubility in common organic solvents such as THF, DMAc, DMF and DMSO.     

Coupling reactions of aryl bromides with 1-alkynols catalysed by a tetraphosphine/palladium catalyst

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ system catalyses efficiently the coupling reactions of aryl halides with a variety of alkynols such as propargyl alcohol, but-1-yn-4-ol, pent-1-yn-5-ol or hex-1-yn-6-ol. The catalyst can be used at low loading. Higher reaction rates were observed in the presence of but-1-yn-4-ol, pent-1-yn-5-ol or hex-1-yn-6-ol than with propargyl alcohol. The protection of the alcohol functions as an ether or a silyloxy group led generally to similar or better results than the reactions performed with the unprotected alcohols.     

含苯侧基杂环聚芳酰胺酰亚胺的合成与性能

聚酰胺酰亚胺 (ＰＡＩ)是一类已商业化的耐热高分子材料 ,具有与聚酰亚胺类似的耐热性能 ,但是改善了聚酰亚胺的溶解性、可加工性能 ,因此进一步开发综合性能优异、加工性能好的聚芳酰胺酰亚胺近年来成为研究热点之一[1～ 3 ] .ＰＡＩ的经典制备方法为 :( 1 )偏苯三酸酰氯与芳香二胺的聚合反应 ;( 2 )含酰亚胺环的偏苯酸和异氰酸酯反应 .近年来聚酰胺酰亚胺又开发了以下途径制备 :( 1 )含亚胺环的二酸与芳香二胺一步缩聚反应 ;( 2 )含亚胺环的芳香二卤代物与二胺的催化羰基化反应等[4～ 6] .本研究组近期合成了一种新型芳香二胺 ,并合成了耐…     

Synthesis of all the four stereoisomers of (1′S)-1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Paulownia bagworm, Clania variegata

All the four stereoisomers of (1′S)-1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Clania variegata, were synthesized by starting from (R)- or (S)-2-methylbutan-1-ol, (R)- or (S)-citronellal, and (S)-2-methylpentan-3-ol. Olefin cross metathesis was employed as the key reaction.     

Gas-phase reactions of NO3 and N2O5 with (Z)-hex-4-en-1-ol, (Z)-hex-3-en-1-ol ('leaf alcohol'), (E)-hex-3-en-1-ol, (Z)-hex-2-en-1-ol and (E)-hex-2-en-1-ol

The night-time atmospheric chemistry of the biogenic volatile organic compounds (Z)-hex-4-en-1-ol, (Z)-hex-3-en-1-ol ('leaf alcohol'), (E)-hex-3-en-1-ol, (Z)-hex-2-en-1-ol and (E)-hex-2-en-1-ol, has been studied at room temperature. Rate coefficients for reactions of the nitrate radical (NO(3)) with these stress-induced plant emissions were measured using the discharge-flow technique. We employed off-axis continuous-wave cavity-enhanced absorption spectroscopy (CEAS) for the detection of NO(3), which enabled us to work in excess of the hexenol compounds over NO(3). The rate coefficients determined were (2.93 +/- 0.58) x 10(-13) cm(3) molecule(-1) s(-1), (2.67 +/- 0.42) x 10(-13) cm(3) molecule(-1) s(-1), (4.43 +/- 0.91) x 10(-13) cm(3) molecule(-1) s(-1), (1.56 +/- 0.24) x 10(-13) cm(3) molecule(-1) s(-1), and (1.30 +/- 0.24) x 10(-13) cm(3) molecule(-1) s(-1) for (Z)-hex-4-en-1-ol, (Z)-hex-3-en-1-ol, (E)-hex-3-en-1-ol, (Z)-hex-2-en-1-ol and (E)-hex-2-en-1-ol. The rate coefficient for the reaction of NO(3) with (Z)-hex-3-en-1-ol agrees with the single published determination of the rate coefficient using a relative method. The other rate coefficients have not been measured before and are compared to estimated values. Relative-rate studies were also performed, but required modification of the standard technique because N(2)O(5) (used as the source of NO(3)) itself reacts with the hexenols. We used varying excesses of NO(2) to determine simultaneously rate coefficients for reactions of NO(3) and N(2)O(5) with (E)-hex-3-en-1-ol of (5.2 +/- 1.8) x 10(-13) cm(3) molecule(-1) s(-1) and (3.1 +/- 2.3) x 10(-18) cm(3) molecule(-1) s(-1). Our new determinations suggest atmospheric lifetimes with respect to NO(3)-initiated oxidation of roughly 1-4 h for the hexenols, comparable with lifetimes estimated for the atmospheric degradation by OH and shorter lifetimes than for attack by O(3). Recent measurements of [N(2)O(5)] suggest that the gas-phase reactions of N(2)O(5) with unsaturated alcohols will not be of importance under usual atmospheric conditions, but they certainly can be in laboratory systems when determining rate coefficients.     

Nonaqueous ionic liquids: superior reaction media for the catalytic Heck-vinylation of chloroarenes

Nonaqueous ionic liquids, that is molten salts, constitute an activating and stabilizing noninnocent solvent for the palladium-catalyzed Heck-vinylation of all types of aryl halides. Especially with chloroarenes an improved activity and stability of almost any known catalyst system is observed as compared to conventional, molecular solvents (e.g. dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP), or dioxane). Thus, even catalytic amounts of ligand-free PdCl2 yield stilbene from technically interesting chlorobenzene and styrene in high yield (turnover number (TON) = 18) without the need for further promoting salt additives such as tetraphenylphosphonium chloride. The scope of the new reaction medium is outlined for the first time for the vinylation of various aryl halides using different mono- and disubstituted olefins as well as a variety of known palladium(0) and palladium(II) catalyst systems. Furthermore, a novel means of catalyst recycling is presented and its scope is evaluated.     

Aryl triflates: useful coupling partners for the direct arylation of heteroaryl derivatives via Pd-catalyzed C-H activation-functionalization

Aryl triflates were found to be suitable partners for the palladium catalyzed direct arylation of heteroaromatics via C-H activation-functionalization. The reaction conditions and the catalyst have a determining influence on the yields. The system combining PPh3 and Pd(OAc)2 using KOAc as base and DMF as solvent promotes the selective 2- or 5-arylations in moderate to high yields. Several heteroaromatics such as furan, thiophene, thiazole or oxazole derivatives have been employed successfully. The electronic properties of the aryl triflates also have a decisive influence on the yields of the coupling products. Electron-rich aryl triflates gave satisfactory results, whereas the electron-poor ones led to the formation of phenols.     

Solvent effects on radical copolymerization of acrylonitrile and methyl acrylate: solvent polarity and solvent-monomer interaction

Abstract

New insights for the effects of organic solvent polarities and solvent-monomer interactions on the radical copolymerization for an important copolymer, poly(acrylonitrile-co-methyl acrylate) (PAN-co-MA), were provided in this research. Solvents, dimethylformamide (DMF), dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO), were used as reaction media. The polarity of these solvents was in the sequence of DMAc?<?DMF?<?DMSO. By studying the reactivity ratios of AN and MA, the triad fractions of the resultant copolymers, the interactions between monomers and solvents, and the compositions of copolymers at various conversions, we concluded that the solvent polarity had minimal influence on the copolymerization of AN and MA, while the solvent-monomer interactions played important roles. The interactions between monomer-monomer, monomer-solvent, and solvent-solvent, were calculated based on quantum chemistry methods. Both theoretical calculations and experimental results suggested that AN and MA in DMSO tended to aggregate locally, while they could be homogeneously dissolved in DMAc and DMF. The interactions between solvent and monomers could cause local monomer concentration variations, or ‘bootstrap’ effect, which is one of the critical factors affecting the copolymerization process of AN and MA and the chemical structures of the resultant polymers.     

Transition-metal-free Suzuki-type coupling reactions: scope and limitations of the methodology

The scope and limitations of the transition-metal-free Suzuki-type coupling of aryl halides and arylboronic acids to form biaryls are presented. Confirmation that the reaction is indeed metal-free is presented. The effects of changing base, solvent, reaction temperature, phase-transfer catalyst, and substrate are shown and the implications of these results discussed in terms of their impact on the synthetic versatility of the methodology. The main findings are that the reaction works well for aryl bromides, water is necessary as a solvent for the reaction, the optimum temperature for the reaction is 150 degrees C, the reaction is best performed by using microwave promotion with the exception of an electron-poor aryl bromide example where conventional heating may be used, only limited boronic acids can be used as coupling partners, sodium carbonate is the best base for the reaction, tetrabutylammonium bromide proves to be the best phase-transfer catalyst for the reaction, the reaction is limited to couplings between aryl halides and aryl boronic acids with sp(2)-sp(3) couplings proving ineffective, and NaBPh(4) can be used in the place of phenylboronic acid as a phenylating agent.     

含氟聚芳醚酮的合成与性能研究

研究了含氟基团的引入对聚醚醚酮(PEEK)的介电常数、溶解性、结晶性和力学性能等的影响.结果表明,这种含氟聚芳醚酮在保持PEEK良好机械性能的条件下,介电常数达到2.7,且频率依赖性小,成膜性能好,成本比相应的含氟PI低5～10倍,有望成为一种极有实用价值的电子封装材料.同时利用合成的含氟单体合成了一系列不同-CF₃取代基含量的聚芳醚酮共聚物,研究了聚芳醚酮共聚物的介电常数与聚合物结构单元中-CF₃取代基含量的关系.结果表明,聚芳醚酮共聚物的介电常数随聚合物结构单元中-CF₃取代基含量的增加而线性降低.     

Utilization of fluorescein sodium salt for the indirect fluorimetric detection in micellar electrokinetic chromatography

The potential of fluorescein sodium salt to generate a background signal in indirect fluorimetric detection in micellar electrokinetic chromatography (MEKC) has been studied by using a sample test containing various alcohols (methanol, ethanol, propan-1-ol, propan-2-ol, 2-methylpropan-1-ol, pentan-3-ol, 2-methylbutan-1-ol, 3-methylbutan-1-ol), acetaldehyde, acetone and ethyl acetate. In order to optimize sample test resolution and detection sensitivity, we have studied different parameters: sodium dodecyl sulfate concentration, electrolyte ionic strength, applied voltage as well as that of the addition of an organic cosolvent within the running electrolyte. Although the micellar pseudo-phase was not able to be saturated with the fluorophore in order to obtain the maximal detection sensitivity, the detection thresholds were satisfactory. By way of example, the detection threshold reached for 3-methylbutan-1-ol is 0.03% (v/v). The quantitative aspect was approached with ethanol titration in a commercial white wine. Finally the repeatability relating to, on the one hand, the effective electrophoretic mobilities and, on the other hand, the corrected areas has also been studied.     

Synthesis of Aryl Allyl Ether in the Recyclable Ionic Liquid [bmim]PF_6

Ionic liquids, especially imidazonium salts, have recently gained recognition as possible environmentally benign alternative chemical process solvents. This is mainly due to their nonvolatile nature, insolubility in some solvents as well as their ability to dissolve a wide range of organic and inorganic materials, allowing the ionic liquids easy recovery and recycling. Examples of their application in organic reactions have been summarized in a number of recent review articles. 1 Aryl allyl et…     

Regioselective synthesis of 1,5-diaryl-1H-imidazoles by palladium-catalyzed direct arylation of 1-aryl-1H-imidazoles

[reaction: see text] A variety of 1,5-diaryl-1H-imidazoles have been regioselectively synthesized by direct coupling of 1-aryl-1H-imidazoles with aryl iodides or bromides in DMF in the presence of CsF as the base and a catalyst precursor consisting of a mixture of Pd(OAc)2 and AsPh3. The data obtained in this synthetic study support a reaction mechanism involving an electrophilic attack of an arylpalladium(II) halide species onto the imidazole ring. Interestingly, some imidazole derivatives synthesized in this study have been found to exhibit significant cytotoxic activity against human tumor cell lines.     

Synthesis and properties of thermally stable and optically active novel wholly aromatic polyesters containing a chiral pendent group

5-(2-Phthalimidyl-3-methyl butanoylamino)isophthalic acid (5), as a novel diacid monomer containing phthalimide and flexible chiral groups, was prepared by the reaction of 2-phthalimidyl-3-methyl butyric acid chloride (4) with 5-aminoisophthalic acid (5AIPA) in dry N,N-dimethylacetamide (DMAc). A series of novel polyesters (PE)s containing phthalimide group was prepared by the reaction of diacid monomer 5 with several aromatic diols via direct polyesterification with the tosyl chloride/pyridine/dimethylformamide (DMF) system as a condensing agent. The resulting new polymers were obtained in good yields with inherent viscosities ranging between 0.37 and 0.61 dL g⁻¹ and were characterized with FT-IR, ¹H NMR, elemental and thermogravimetric analysis techniques. These polymers are readily soluble in amide type solvents such as DMAc, DMF, 1-methyl-2-pyrrolidone, hexamethyl triaminophosphine, dimethyl sulfoxide and protic solvents such as sulfuric acid. Thermogravimetric analysis showed that the 10% weight loss temperature in a nitrogen atmosphere was more than 345 °C, which indicates that the resulting PEs have a good thermal stability as well as excellent solubility.     

N-picolinamides as ligands for Ullmann-type homocoupling reactions

The use of N-phenylpicolinamide (NPPA) as a ligand in Ullmann-type homocoupling reactions of aryl iodides and bromides in common solvents, such as DMF and MeCN has been successfully demonstrated at room temperature. In addition, this work provided the first example of the homocoupling of an aryl chloride at 82 °C, which is a relatively low temperature when compared to regular Ullmann reaction temperatures. Also, NPPA was successfully employed in base—and heat free Suzuki reactions, including electron rich and poor aryl halides with heteroarylboronic acids in moderate yields.