离子交换色谱分离-紫外检测法测定吡啶离子液体阳离子

建立了用离子交换色谱分离-紫外检测法测定N-乙基吡啶、N-丁基吡啶和N-丁基四甲基吡啶3种吡啶离子液体阳离子的方法。采用磺酸型阳离子交换柱,以乙二胺-柠檬酸-乙腈为流动相,研究了流动相和色谱柱温度对离子保留行为的影响和规律。实验发现,吡啶阳离子的保留过程是放热过程。优化后的色谱条件:流动相为乙二胺(0.2 mmol//L)-柠檬酸(0.3 mmol//L)-乙腈(0.5%,v/v,pH=4.2),流动相流速为1.0mL/min,色谱柱为Shim-pack IC-C1阳离子交换柱,色谱柱温度为30℃。在此条件下3种吡啶阳离子可以达到基线分离。所测阳离子的检出限(S/N=3)分别为0.01、0.01、0.02mg/L,峰面积的相对标准偏差(n=5)小于0.8%。紫外检测法测定化学实验室合成的吡啶离子液体样品,样品加标后测得的加标回收率在96.3%~104%。方法准确、可靠、快速,具有较好的实用价值。     

离子色谱-直接电导检测法分析哌啶离子液体阳离子

建立了离子色谱-直接电导检测法分析N-甲基,乙基哌啶(［MEPi］+)、N-甲基,丙基哌啶(［MPPi］+)和N-甲基,丁基哌啶(［MBPi］+) 3种哌啶离子液体阳离子的方法。采用磺酸型阳离子交换色谱柱,以乙二胺-柠檬酸-乙腈为流动相。考察了流动相组成及色谱柱温度对哌啶阳离子保留的影响,并讨论了保留规律。结果表明,哌啶阳离子的保留是一个放热过程,即哌啶阳离子的保留时间随着色谱柱温度的升高而缩短,且哌啶阳离子同系物的保留符合碳数规律。在以0.2 mmol/L乙二胺-0.3 mmol/L柠檬酸-3%(v/v)乙腈(pH 4.4)为流动相、流速1.0 mL/min、柱温30 ℃条件下,［MEPi］+、［MPPi］+和［MBPi］+3种哌啶阳离子可以在7 min内分离,检出限(信噪比为3)分别为0.14、0.20和0.56 mg/L,峰面积的相对标准偏差(n=5)在1.2%以下。将此方法应用于分析实验室合成的哌啶离子液体样品,加标回收率在97.6%与105.1%之间。本方法准确、可靠、快速,具有较好的实用性。     

吡啶离子液体阳离子的离子色谱法分析

建立了离子色谱-直接电导检测法分离测定3种吡啶离子液体阳离子(N-乙基吡啶、N-丁基吡啶和N-己基吡啶阳离子)的方法.采用磺酸型阳离子交换色谱柱,以乙二胺-柠檬酸-乙腈为淋洗液,考察了淋洗液种类和浓度以及色谱柱温度对离子液体阳离子保留的影响.实验发现,吡啶阳离子的保留过程是放热过程,其同系物的保留符合碳数规律.优化的色...     

同系物季铵盐离子液体阳离子的离子交换色谱法分析

建立了离子交换色谱-直接电导检测法分离测定3种同系物季铵盐离子液体阳离子(四甲基铵、四乙基铵和四丙基铵阳离子)的方法。采用磺酸型阳离子交换色谱柱,以乙二胺-柠檬酸-乙腈为淋洗液,考察了淋洗液种类、浓度及色谱柱温度对3种阳离子保留的影响。并根据测定对象不同,调整乙二胺浓度及乙腈含量以改善分离效果。淋洗液中增加乙腈含量,可明显缩短四丙基铵阳离子的保留时间,并改善其色谱峰形。季铵阳离子同系物的保留符合碳数规律。优化的色谱条件为:流速1.0 mL/min,色谱柱温度40℃;以0.02 mmol/L乙二胺-0.12 mmol/L柠檬酸(pH 4.0)为淋洗液分离测定四甲基铵;以0.2 mmol/L乙二胺-0.4 mmol/L柠檬酸-1%乙腈(pH 4.0)为淋洗液分离测定四乙基铵和四丙基铵。所测阳离子的检出限(S/N=3)分别为0.015,0.22,1.88 mg/L,相对标准偏差(n=5)均小于2.3%。将方法应用于表面活性剂和实验室合成的离子液体的分析,加标回收率为99%~104%。本方法简单、准确、可靠,具有良好的实用性。     

离子色谱-直接电导检测法分离测定吗啉离子液体阳离子

建立了离子色谱-直接电导检测法分析N-甲基乙基吗啉([MEMo]+)、N-甲基丙基吗啉([MPMo]+)2种吗啉离子液体阳离子的方法。采用磺酸型阳离子交换色谱柱,以乙二胺-乙腈为流动相,研究了色谱柱、流动相、色谱柱温度对吗啉阳离子保留的影响,并讨论了保留规律。结果表明,吗啉阳离子的保留基本属于离子交换模式,是一个放热过程。在柱温30℃,流速1.0 mL/min,以0.1 mmol/L乙二胺-0.5%乙腈(用盐酸调节至pH 5.0)为流动相条件下,[MEMo]+和[MPMo]+阳离子可在4 min内得到基线分离,检出限(S/N=3)分别为0.08、0.13 mg/L,峰面积的相对标准偏差(RSD,n=5)不大于1.5%。将此方法用于测定实验室合成的吗啉离子液体样品,加标回收率为94.0%～106.0%。方法准确、可靠、快速,具有较好的实用性,可满足离子液体样品的检测要求。     

离子对色谱法同时分离测定吡啶及咪唑离子液体阳离子

建立了用紫外检测的反相离子对色谱梯度淋洗同时分离测定4种吡啶离子液体阳离子和5种咪唑离子液体阳离子的方法。实验采用ZORBAX Eclipse XDB-C18反相色谱柱,以离子对试剂水溶液(用柠檬酸调节pH值)+乙腈为流动相,考察了离子对试剂种类和浓度、乙腈浓度和色谱柱温度对保留的影响,探讨了相关保留规律,确定最佳色谱条件为:流速1.0 mL/min、柱温30℃,以1.0 mmol/L庚烷磺酸钠水溶液(pH 4.0)-乙腈为淋洗液进行梯度洗脱。在此条件下,4种吡啶阳离子和5种咪唑阳离子在15 min内达到基线分离。检出限(S/N=3)为0.31～0.54 mg/L,峰面积的相对标准偏差为0.10%～0.75%。将该方法用于实验室合成的离子液体样品分析,加标回收率为94%～98%。该方法准确、可靠,具有较好的实用性。     

整体柱离子对色谱-间接紫外检测法快速分析吡咯烷离子液体阳离子

建立了快速分析无紫外光吸收的吡咯烷离子液体阳离子的离子对色谱-间接紫外检测法。采用反相硅胶整体柱,以(背景紫外吸收试剂-离子对试剂)水溶液-有机溶剂为流动相,分别讨论了背景紫外吸收试剂、检测波长、离子对试剂、有机溶剂、柱温及流速对分离测定吡咯烷阳离子的影响。最佳色谱条件为:以80%(V/V)(0.5 mmol/L对氨基苯酚盐酸盐-0.1 mmol/L庚烷磺酸钠)水溶液-20%(V/V)甲醇为流动相,检测波长230 nm,柱温30℃,流速2.0 mL/min。在此条件下,N-甲基,乙基吡咯烷阳离子、N-甲基,丙基吡咯烷阳离子和N-甲基,丁基吡咯烷阳离子在1.6 min之内基线分离,检出限(S/N=3)分别为0.02,0.03和0.07 mg/L,相对标准偏差(n=5)小于0.4%。将此方法用于分析实验室合成的离子液体样品,加标回收率在97.4%～98.0%之间。本方法快速、简单、准确、可靠,具有良好的实用性。     

咪唑离子液体作为流动相添加剂的整体柱离子对色谱快速分析哌啶阳离子

以咪唑离子液体作为流动相添加剂,建立了哌啶离子液体阳离子的整体柱离子对色谱-间接紫外检测分析方法。系统研究了流动相、流速等因素对哌啶阳离子分离测定的影响情况。流动相中的咪唑离子液体不仅起到了背景紫外吸收剂的作用,还改善了阳离子的分离效果。用0.5mmol/L 1-乙基-3-甲基咪唑四氟硼酸盐-0.1mmol/L庚烷磺酸盐水溶液(pH=4.5)/甲醇(90/10,V/V)作为流动相,流速3.0mL/min,检测波长210nm,N-甲基-N-乙基、N-甲基-N-丙基和N-甲基-N-丁基哌啶阳离子在3.0min之内实现基线分离。3种哌啶阳离子的检出限分别为0.13、0.34和0.42mg/L。该方法测定实验室合成的哌啶离子液体样品的加标回收率范围为94%~98%。     

反相离子对色谱-直接电导检测法分析六氟磷酸根离子液体阴离子

建立了反相离子对色谱-直接电导检测六氟磷酸根(PF6-)离子液体阴离子的分析方法。用DiamonsilC18反相色谱柱为分离柱,以离子对试剂-柠檬酸-乙腈混合水溶液为流动相,考察了离子对试剂、乙腈含量、pH值及色谱柱温度对六氟磷酸根保留的影响,并讨论了相关保留机理。在优化的色谱条件下,即流动相为0.05 mmol/L氢氧化四丁铵-0.038 mmol/L柠檬酸-35%乙腈(pH 5.5),流速1.0 mL/min,色谱柱温度40℃时,PF6-与其它常见阴离子(F-、Cl-、Br-、NO3-、SO24-、BF4-)达到基线分离且保留时间在15 min内。方法检出限(S/N=3)为0.25 mg/L,标准曲线的线性范围为0.5～100.0 mg/L,峰面积和保留时间的相对标准偏差(n=5)分别为0.17%和0.15%。该法用于1-丁基-3-甲基咪唑六氟磷酸盐和1-丙基-2,3-二甲基咪唑六氟磷酸盐两种离子液体中PF6-的测定,加标回收率分别为99%和104%。该方法简单、准确、可靠,实用性好。     

离子液体为流动相的液相色谱法-间接紫外检测吗啉阳离子

建立了以咪唑离子液体为流动相的液相色谱-间接紫外检测分析N-甲基,丙基吗啉阳离子的方法。用反相硅胶整体柱,以咪唑离子液体-离子对试剂水溶液/有机溶剂为流动相测定吗啉阳离子。咪唑离子液体为背景紫外吸收试剂。研究了咪唑离子液体、检测波长、离子对试剂、有机溶剂、柱温、流速对测定吗啉阳离子的影响,探讨了保留规律。以0.5 mmol·L-11-乙基-3-甲基咪唑四氟硼酸盐-0.1 mmol·L-1庚烷磺酸钠水溶液/甲醇(85∶15,v/v)为流动相,检测波长210 nm,柱温30℃,流速1.0 m L·min-1,N-甲基,丙基吗啉阳离子的保留时间为2.397 min,检出限(S/N=3)为0.02 mg·L-1,峰面积的相对标准偏差(n=5)为1.1%,保留时间的相对标准偏差(n=5)为0.03%。将此方法用于分析实验室合成的N-甲基,丙基吗啉离子液体,加标回收率为100.5%。本方法简便、快捷,可满足N-甲基,丙基吗啉离子液体阳离子的定量分析要求。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.