双硫碳阴离子与溴乙酸烷基酯的反应

双硫碳阴离子1是一个极为有用的合成原(Synthon),它在合成化学中已得到广泛应用。1通常与单官能团亲电试剂反应能产生满意的结果~([3a]),我们用此法从环氧乙烷成功地合成了化合物2a~([3b])。1与双官能团化合物的反应,例如与N,N-二乙基溴乙酰胺~([1b])或β-溴丙酸乙酯~([4])的反应均能得到溴被取代的产物,得率分别为50%和74%。这可能是由于酰氨羰基的不活泼性(前者)和β-溴丙酸酯的烯醇化使溴原子处于活泼的烯丙位(后者),从而有利于1进攻与溴相连的碳原子。本文报道1与滇乙酸烷基酯的反应以制备溴被取代的产物2b。1与溴乙酸叔丁酯反应,主要得到溴被取代的2-(3′-硫杂戊基)-2-叔丁氧甲酰甲基-1,3-二硫杂环己烷(3),得率70%;若与溴乙酸甲酯或乙酯反     

手性铝配合物远程精准控制镍催化合成手性茚衍生物

正具有全碳取代四级立体中心的手性茚化合物是生物活性分子及有机材料的重要结构基体之一~([1]).目前此类化合物的立体选择性构筑方法主要有两种,一是对茚衍生物的直接不对称官能化(Scheme1a),Boche-Hoppe~([2]),Jorgensen~([3])和张俊良~([4])等在这方面进行了一系列     

气相色谱法测定挤塑聚苯乙烯泡沫塑料中3种发泡剂的残留量

正目前,挤塑聚苯乙烯泡沫主要作为保温材料和防潮材料运用于墙体、屋面、地面、冷库和道路等地方~([1]),常用发泡剂有氢氟氯烃、氢氟烃、烃类、二氧化碳~([2]),由于挤塑聚苯乙烯泡沫是内部完全闭孔发泡,发泡剂基本上留在泡孔内~([3])。氢氟氯烃释放到环境中会造成臭氧空洞和温室效应,目前主要对海水~([4])和空气~([5])中氢氟氯烃进行检测。我国自加入蒙特利尔公约后,加快了无氟取代的进程,体现在聚氨酯泡     

固相萃取-高效液相色谱法测定水中3种有机磷农药残留

<正>丙溴磷、三唑磷和毒死蜱是3种高效杀虫剂。丙溴磷是一种分子内含有正丙硫基的硫代磷酸酯类中等毒性杀虫剂,作用迅速,药剂吸着力强,对产生抗性的害虫有杀灭的效果~([1])。三唑磷是高效的有机磷杀虫、杀螨剂~([2]),对危害粮食、果蔬等农作物的害虫有良好的防治效果。毒死蜱是乙酰胆碱酯酶抑制剂,属硫逐磷酸酯类中等毒性杀虫剂,对棉铃虫有预防效果~([3-4])。在甲胺磷、对硫磷等有机磷杀虫剂被禁     

高效液相色谱-串联离子阱质谱法快速测定减肥类保健品中西布曲明的含量北大核心CSCD

西布曲明具有减肥的作用^([1]),但会导致头痛、失眠等不良反应^([2]),甚至增加心脏病的风险^([3])。我国已于2010年明令禁止西布曲明在国内生产和销售^([4]),但一些不法厂商为提高减肥类保健品的效果而添加西布曲明并在网络销售的事件屡见不鲜^([5])。     

青蒿素及其一类物结构和合成的研究——Ⅸ.全合成青蒿素中若干关键化合物的合成

青蒿素是一个含有过氧基团的新型倍半萜内酯~([1]),它具有突出的抗疟作用~([2])。本文报道     

乙二胺四乙酸容量法测定高锡锑铋渣中的铋

<正>铋作为一种享有"绿色金属"~([1])之称的金属,也是逆磁性最强的金属,在磁场作用下电阻增大而导电率下降。它的合金有热电效应,与硒、碲的化合物具有半导体性质~([2]),可见其用途非常广泛。工业上常用的焊接原材料焊锡中就含有金属铋~([3])。医学上用的一些止泻药、骨片、眼影膏、唇膏都含有少许的铋。同时铋也可作为合金的添加剂、核子反应堆中载体热体或冷却剂~([4])。目前,铋的测定方法有光度     

酸溶-碱提取-硫氰酸盐分光光度法测定岩石矿物中的钼含量

<正>钼在地壳中的质量分数约为3μg·g~(-1),自然界中已知的含钼矿物约有30余种~([1]),目前岩石矿物中钼的测定方法主要有重量法~([2])、容量法~([3])、分光光度法~([4-6])、原子吸收光谱法~([7-9])、电感耦合等离子体质谱法~([10-12])和电感耦合等离子体原子发射光谱法~([13-15])等。重量法和容量法操作繁琐,仅适用于钼     

水合六硼酸钡的合成与热化学研究

硼原子的硼酸盐种类繁多,结构复杂多样,其中,有一些硼酸盐具有特殊的性能,如:2ZnO·3B_2O_3·3.5H_2O、2CaO·3B_2O_3·5H_2O可用作阻燃材料~([1]),β-BaB_2O_4(β-BBO)~([2])、Ba_2Be_2B_2O_7~([3])、BaAl_2 B_2O7_~([4])等因其具有良好的光学性质,被广泛用作非线性光学材料.因此,进行硼酸盐的合成及性质研究有着重要的意义.     

萘环上取代基的迫位效应

在萘分子中,1-位和8-位称为迫位。在1-位和8-位上的取代基间的距离比其与邻位间的取代基更加接近。这种近邻效应使得迫位取代的萘具有特殊的性质。五十年代以来,合成了很多以萘为母体的化合物,它们的物理化学性能和实用价值引起了化学家们的很大兴趣。本文只讨论在萘环1,8-位上有取代基的化合物及迫位取代基的相互作用。由于迫位上取代基间空间和电子效应交织在一起,使这类化合物表现出许多反常的物理化学行为,因此,对迫位效应的了解将有助于我们对反应机制的正确理解和对反常现象的合理解释。这类化合物的结晶结构已有许多论述~([1-11]),它们的核磁共振和红外光谱也有许多文献报导~([12,18,38,39]),这里不作主要介绍。一、萘衍生物的迫位环化在许多已知反应中,由于迫位上取代基的相互作用,或取代基与添加剂作用,跨过迫位生成许多环状化合物,环的大小通常为四元环至八元环。1,8-二羟基萘在非氧化条件下脱水,生成四元环化合物(1)~([45]),萘环砜(2)的合成也有报导~([14])。     

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.