经过极性反转的亲核有机催化

总结了近几年来经过极性反转的有机催化的研究近展, 概括了以C, N, P, S为中心的各种亲核催化剂的催化机理及催化性能. 通过对不同类别及同类不同活性中心的催化剂的比较分析, 简要概括了各种催化剂的优劣势, 并对极性反转的有机过程进行了机理上的阐述.     

对映选择性亲电氟化反应研究进展

含氟有机化合物, 特别是手性氟化物在医药、农药及功能性材料等相关领域的作用备受注目. 尽管在分子中有立体选择性地引入一个氟原子一直是有机化学家面临的一个挑战性问题, 近年来在化学家们的不断努力下, 对映选择性氟化反应研究取得重要进展. 高光学活性的手性氟化物可通过手性亲电氟化试剂诱导的立体选择性氟化反应, 基于底物的手性氟化反应以及手性催化剂诱导的不对称催化氟化反应等来制备. 特别是, 手性金属配合物和有机催化剂诱导的不对称催化氟化反应被广泛应用于各类手性氟化物的合成, 已成为不对称氟化反应研究的热点. 全面介绍对映选择性亲电氟化反应研究概况和最新进展, 讨论各种不对称氟化反应的特点及应用范围.     

磷亲核试剂对缺电子烯烃不对称共轭加成反应的进展

手性膦化合物在不对称催化、药物、材料等领域有着广泛的用途.手性膦可作为配体与金属配位或作为有机催化剂用来催化合成光学活性化合物.含膦亲核试剂对缺电子烯烃的不对称共轭加成反应可以用来直接构建手性膦化合物.总结了该领域近年来的主要研究进展,介绍了几类重要的过渡金属催化剂以及小分子催化剂促进的缺电子烯烃的不对称氢膦化反应.     

N-杂环卡宾催化对氟硝基苯和苯甲醛的亲核酰基化反应研究

以咪唑类离子液体为N-杂环卡宾(NHC)催化剂的前体,应用于催化芳基氟化物和醛的亲核酰基化反应,成功地将酰基直接引入到缺电子的芳环上,制备出含吸电子基团的芳香酮.以对氟硝基苯和苯甲醛的反应制备对硝基二苯甲酮为模板,详细探讨了NHC催化的亲核酰基化反应的机理和反应规律,优化出最佳反应条件,并考察了催化剂的循环使用效果.实验结果表明,以DMSO为溶剂、离子液体1(R=n-C12H25)为催化剂前体、叔丁醇钾为碱,离子液体的用量为对氟硝基苯的33 mol%,离子液体和叔丁醇钾的物质的量比为1:4,反应温度为30℃,反应时间为6 h,对氟硝基苯的转化率可达93.0%,对硝基二苯甲酮的收率为88.6%.离子液体循环使用4次,对硝基二苯甲酮的收率仍在75%以上.     

烷基铝试剂与亲电试剂的偶联反应研究进展

烷基铝试剂因其反应活性高、毒性低、易于制备,广泛应用于有机反应中.过渡金属催化或无催化剂的条件下,有机铝试剂与亲电试剂的交叉偶联反应为多种化合物的合成提供了一种简便的方法,并显示出比有机锂和有机镁试剂更高的官能团耐受性,可以在硝基、酯基、羟基、氨基、腈基和内酯的存在下与羰基进行加成反应,与亲电试剂进行偶联反应.近年来许...     

以手性两亲小分子为模板剂制备介孔二氧化硅纳米空心球

以L-亮氨酸为手性源合成了手性阳离子两亲性小分子化合物L-18Leu6NEtBr,用其自组装体作为模板,氢氧化钠为催化剂,经溶胶-凝胶过程制备出介孔二氧化硅纳米空心球;分析了介孔二氧化硅纳米空心球的尺寸和孔径.结果表明,所制备的二氧化硅空心球直径约100nm;其介孔孔道平行于壳表面,孔径为3.1nm.     

二氟烯醇硅醚参与的高效“在水上”无催化剂亲核加成反应:显著的氟效应

正Angew.Chem.Int.Ed.2014,53,9512~9516尽管C—F…H—X相互作用已通过单晶结构分析和理论计算得以证实,但利用这一弱相互作用来改善有机反应活性的研究才刚起步.最近,华东师范大学周剑课题组设想利用部分氟代的亲核试剂与水分子之间的C—F…H—O相互作用,结合界面水分子对亲电试剂的氢键作用,来实现一些"在水上"的无催化剂反应,为选择性合成含氟化合物提供一些高效方法.基于这一设想,他们发展了"在水上"的无需催化剂的二氟烯醇硅醚1与醛、高活性的酮以     

单壁碳纳米管与卤代烷的亲电加成反应

主要考察了以路易斯酸为催化剂,几种卤代烷烃为反应试剂的单壁碳纳米管侧壁的亲电加成反应,并通过傅立叶红外光谱、热失重分析和拉曼光谱验证了实验所得产物。此反应的目的是在单壁碳纳米管的侧壁连上烷基基团以提高其溶解性和分散性,并可使其更好地与聚烯烃相结合从而提高复合材料的性能,因而具有较高的研究和应用价值。     

手性双官能硫族化合物催化烯烃的不对称亲电硫化反应

手性含硫化合物在药物化学和不对称合成领域中应用广泛,发展这类化合物的新合成方法是有机合成化学的重要任务.烯烃的不对称亲电硫化反应为手性含硫化合物的合成提供了一条方便的途径,通过这种方式不仅可以在烯烃母体分子上引入一个含硫基团,同时也能够引入另外一个重要的官能团.我们课题组设计、合成了一系列手性双官能硒醚/硫醚催化剂,并...     

新型手性亲核催化剂4-二甲胺基吡啶衍生物的研究进展

手性4-二甲胺基吡啶(DMAP, 4-Dimethylaminopyridine)衍生物作为具有较高催化活性和对映选择性的新型手性亲核催化剂, 已经在多种不对称催化反应中得到应用, 并取得了很好的研究成果. 目前, 手性DMAP衍生物化学的研究正成为催化不对称合成领域中一个十分活跃和引人注目的研究热点. 综述了手性DMAP衍生物化学近几年的研究进展.     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.