Organocatalytic synthesis of α-quaternary amino acid derivatives via aza-Friedel-Crafts alkylation of indoles with simple α-amidoacrylates

The first (organo)catalytic method for regio- and chemoselective aza-Friedel-Crafts (FC) alkylation of indoles and pyrroles with commercially available methyl α-acetamidoacrylates has been discovered. It minimizes/eliminates common competing reactions that occur due to the high and multiatom-nucleophilic character of indole and pyrrole. Diverse quaternary α-amino acids were successfully prepared in good yield and high selectivity using low catalyst loading. The enantioselective variant using BINOL-derived phosphoric acids was also explored with indole providing the desired F-C alkylation product with moderate enantioselectivities.     

十二烷基磺酸铁催化合成丙酸正丁酯

以十二烷基磺酸铁催化合成了丙酸正丁酯。实验结果表明最佳反应条件为：丙酸100mmol,n(丙酸)：n(正丁醇)=1．0：1．2,十二烷基磺酸铁0．8g(约1．0mmol),带水剂环己烷6mL,回流分水60min,酯化率94．6％。催化剂重复使用5次仍保持较高活性。     

Synthesis of fulleropyrrolidines through the reaction of [60]fullerene with quaternary ammonium salts and amino acids

The reactions of [60]fullerene with amino acids and quaternary ammonium salts in toluene afforded two fulleropyrrolidine derivatives. One fulleropyrrolidine derivative contained a RCH moiety originating from quaternary ammonium salts through C–N bond cleavages and other fulleropyrrolidine derivatives contained a PhCH moiety originating from toluene through C–H bond cleavage. By using chlorobenzene instead of toluene as solvent, only one fulleropyrrolidine derivative containing a RCH moiety was obtained in the reactions.     

Synthesis of the four diastereoisomers of 3-thymine-1-(butoxycarbonyl)aminocyclopentane-1-carboxylic acid

Synthetic routes to all four diastereoisomers of 3-thymine-1-(^tbutoxycarbonyl)aminocyclopentane-1-carboxylic acid have been developed starting from the commercially available (S)-dimethyl malate. The key step in the synthesis involves dialkylation of N-(diphenylmethylene)glycine ethyl ester with 1,4-diiodo-2(S)-trityloxybutane.     

Synthesis and properties of long-chain quaternary ammonium hydroxides

A series of long-chain quaternary ammonium hydroxides were synthesized from tertiary amines and confirmed by ~1H NMR and FTIR.Surface properties and pH of these surfactants were investigated.The critical micelle concentrations(CMC) of the synthesized quaternary ammonium hydroxides are lower than the conventional quaternary ammonium surfactants.The micelles shapes of these long-chain quaternary ammonium hydroxides in aqueous solution are spherical at a concentration of 0.1 mol/L.The pH values of the synthesized quaternary ammonium hydroxides are 12.25-12.51.     

Synthesis of novel quaternary ammonium surfactants containing adamantane

A series of novel quaternary ammonium surfactants containing adamantane were designed and synthesized from 1-adamantanecarboxylic acid.The structures of target surfactants were confirmed by]H NMR,elements analysis and FTIR.Surface properties of these surfactants were investigated.Due to the lipophilicity of adamantane,the critical micelle concentration（CMC） and C₂₀ values of the synthesized quaternary ammonium surfactants are lower than that of conventional quaternary ammonium surfactants.     

Ferric chloride-promoted direct trifluoromethylselenolation of nitrogen-containing heterocyclic compounds by Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate in water

The ferric chloride-promoted direct trifluoromethylselenolation of indoles and other nitrogen-containing heterocyclic compounds in water was performed by employing TsSeCF₃ as a trifluoromethylselenolation reagent. The shelf-stable and readily accessible reagents, along with the environmentally friendly and mild reaction conditions make this method an effective alternative for the trifluoromethylselenolation of electron-rich aromatics.     

季铵类离子液体催化熔融缩聚反应合成异山梨醇基聚碳酸酯

聚碳酸酯是一种性能优良的工程塑料,具有优异的透明性、绝缘性及无毒性等优点.目前实现大规模工业生产的是双酚A型聚碳酸酯,但是其生产原料双酚A具有毒性,限制了其应用.异山梨醇是一种生物基可再生单体,具有无毒、手性和刚性等特性,是双酚A的理想替代品.但是异山梨醇亲水性强,且羟基的活性低,导致碳酸二苯酯和异山梨醇通过熔融缩聚反应合成异山梨醇基聚碳酸酯(PIC)困难,因此选用合适的催化剂成为一个重要因素.目前报道的效果较好的催化剂是无机碱催化剂,这类催化剂催化活性差,容易引发副反应,在产品中残留影响产品质量.离子液体具有环境友好和阴阳离子可设计等优点,是无机碱催化剂的良好替代品.本文设计合成了六种季铵类的碱性离子液体(四乙铵二氰胺盐、四乙铵咪唑盐、四乙铵乳酸盐、四乙铵-1,2,4-三氮唑盐、四乙铵苯甲酸盐和四乙铵乙酸盐),用于催化熔融缩聚反应合成PIC.用核磁共振表征了PIC的结构,用凝胶色谱测定了PIC的分子量,通过对比PIC的重均分子量(Mw)和异山梨醇的转化率,研究了离子液体阴离子对催化剂活性的影响.发现催化活性不仅与离子液体的碱性强弱有关,还与离子液体阴离子的配位强度有关,催化效果最好的离子液体为四乙铵咪唑盐(TEAI).以TEAI为催化剂对合成PIC的条件进行了优化,得到的最优条件为:催化剂与异山梨醇的摩尔比为5×10-4,缩聚时间为5 h,缩聚温度为240 oC.合成PIC的Mw为25600 g/mol,异山梨醇的转化率为92%.由于均聚物PIC分子链刚性大,导致PIC熔体粘度大,不利于聚合,为了降低PIC的刚性和提高分子量,在分子链中引入了柔性基团(脂肪族二醇)来合成共聚碳酸酯(PAIC).以TEAI为催化剂,异山梨醇和脂肪族二醇投料摩尔比为1:1,通过熔融缩聚反应合成了PAICs.利用1H NMR和13C NMR详细表征了PAICs化学组成和微观结构,发现不同脂肪族二醇的羟基活性不同,合成的PAICs分子链中异山梨醇和脂肪族二醇的比例与投料比有所差异,得到的共聚物为无规共聚物.此外,对PAICs进行了凝胶色谱测试,发现PAICs的Mw与PIC相比均有所提高.通过差示扫描量热仪和热重分析仪对PIC和PAICs进行了热稳定性测试.结果表明,对于不同直链二醇制备的PAICs,随着二醇链中亚甲基数量的增加,其玻璃化转变温度(Tg)逐渐降低,但热稳定性逐渐提高;而对于用1,4-环己烷二甲醇合成的PCIC,其Tg值和热稳定性明显高于直链脂肪族二醇共聚物.这些性能为共聚碳酸酯用作高性能聚合材料提供了可能性.     

Span/Tween混合表面活性剂微乳液制备纳米铁及脱硝研究

研究了以Span 80和Tween 60为混合表面活性剂的微乳液的形成。以电导率及目测法为表征手段,利用正交试验,分析了多因素对W/O型微乳液最大增容水量的影响,探明了该乳液形成的适宜条件。     

铁纳米粒子共振光散射测定纳克级核酸

核酸作为生物遗传的物质基础,对其进行分析化学研究一直备受关注.当前,微流控分析技术的快速发展为核酸的高灵敏检测展示了新的前景.     

Tishchenko reactions and Oppenauer oxidation reactions of aldehydes promoted by diisobutylaluminum hydride

The aliphatic aldehydes react with catalytic amount of Dibal-H in n-pentane to give the corresponding Tishchenko products in good to excellent yields. Contrary, α-silyloxyaldehydes give α-silyloxyketones via Oppenauer oxidation under similar condition.     

Synthesis and characterization of quaternary ammonium dicarboxylic acid isoelectric buffers and their use in pH-biased isoelectric trapping separations

Two approaches are described in this paper for the synthesis of isoelectric buffers that have pI values in the 1.5 < pI < 4.3 range. The first synthesis relies on the alkylation of existing aminodicarboxylic acids and recovery of the ampholyte as an inner salt. The second synthesis method forms low-pI ampholytes by reacting a secondary amine with two equivalents of an alkylester of a haloalkanecarboxylic acid, followed by hydrolysis of the intermediate in an alkaline solution and recovery of the ampholyte as an inner salt. The new ampholytes have been analytically characterized by capillary electrophoresis, high-resolution electrospray ionization-mass spectrometry, one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy, and X-ray crystallography. The isoionic solutions of the new ampholytes have high buffering capacity and conductivity, making them good pH biasers in the receiving stream in preparative-scale pH-biased isoelectric trapping separations.     

光化学动力学法测定硝酸盐和亚硝酸盐

本文研究了甲基橙动力学法测定水、食品及蔬菜中硝酸盐和亚硝酸盐。在紫外光照射下甲基橙退色程度与硝酸盐和亚硝酸盐含量成正比。文中提出首先测定二者的总量,然后在氨基磺酸存在下测定硝酸盐的量,再差减求得亚硝酸盐的量。     

Synthesis of fluorinated glutamic acid derivatives via vinylalumination

A variety of structural types of fluorinated allylic acetates, prepared by vinylalumination of fluorinated aldehydes, were reacted with the benzophenone imine of glycine tert-butyl ester to provide 4-(fluorobenzylidenyl)- and 4-(fluoroalkylidenyl) glutamic acid derivatives in 61-96% yield. The 4-(4-fluorobenzylidenyl) glutamic acid derivative was hydrolyzed to give the 4-(4-fluorobenzylidenyl)pyroglutamate and then hydrogenated to the 4-(4-fluorobenzyl)pyroglutamate. The catalytic enantioselective conjugate addition-elimination of the benzophenone imine of glycine tert-butyl ester with the fluorinated allylic acetates prepared from fluoral, pentafluorobenzaldehyde, and 2,6-difluorobenzaldehyde provided the corresponding 4-(fluoroalkylidenyl)- and 4-(fluorobenzylidenyl) glutamic acid derivatives in 42, 45 and 80% ee, respectively.     

Ferric chloride/tetraethyl orthosilicate as an efficient system for synthesis of dihydropyrimidinones by Biginelli reaction

An efficient method for the Biginelli reaction of aldehydes, acetoacetate esters and urea employing tetraethyl orthosilicate in the presence of ferric chloride is described. These improved reaction conditions allow the preparation of a wide variety of substituted dihydropyrimidinones (including sterically encumbered ones) in high yields and purity under mild reaction conditions.     

离子对分离和抑制电导检测法测定四乙基铵和四丁基铵根离子

建立了季铵盐的离子色谱分析方法.采用Dionex DX-500 型离子色谱仪,C18柱,电导检测器,以30%乙腈和10 mmol/L甲烷磺酸混合溶液为流动相,流量为1.00 mL/min.四乙基溴化铵和四丁基溴化铵的质量浓度和峰面积的相关系数分别为0.9996和0.9994;线性范围分别为10～80 mg/L和20～120 mg/L;检出限分别为0.28和0.76 mg/L;RSD分别为1.3%、 2.5%.该方法可用于分析水溶液中季铵盐的含量.     

Synthesis of 4-aminomethyl-tetrahydrofuran-2-carboxylates with 2,4-cis and 2,4-trans relationships

Templated tetrahydrofuran-based γ-azido esters were prepared with the C-2 and C-4 functionalities in cis and trans relative configurations. This was achieved by ring contraction of the suitably protected 2-O-triflates of pentono-1,5-lactones (d-ribose and l-arabinose) with subsequent introduction of the azide via the 4-O-triflate. Access to a corresponding β-azido ester was achieved in good yield. Little elimination product was observed by introduction of the azide via the 3-O-triflate. These azido esters are scaffolds, which may be predisposed to adopt secondary structural motifs, for example, for use as peptidomimetics; they may also be utilised for the preparation of stereodiverse compound libraries.