手性Lewis酸催化的三甲基镓对醛的不对称加成反应

不对称碳碳键的形成是不对称催化中最活跃的领域之一,其中,二乙基锌对醛的加成一直受到广泛关注.但是最简单的甲基化试剂对醛的加成却很少提及到.有机镓铟的化合物早在1932年就已经被合成出来了,然而它们在有机合成中的应用却很少.因为它们对亲电试剂的活性较低,而且对水,空气很不稳定.我们在研究中发现,在强的Lewis酸(TiCl4)的催化下,三甲基镓能对醛进行加成,得到甲基醇.我们使用手性叔胺为手性配体,与TiCl4来催化三甲基镓对醛的加成,可以得到具有光学活性的甲基醇,首次实现了以GaMe3为烷基化试剂对醛的不对称加成反应.     

碳亲核试剂对氮杂环丙烷的开环反应研究进展

综述了各种碳亲核试剂对氮杂环丙烷的开环反应研究进展,主要包括炔、腈、芳烃、芳香杂环化合物、活泼亚甲基和有机金属试剂等作为碳亲核试剂发生的开环反应,并对其发展方向进行了展望.     

铜催化的共轭硅化反应的研究进展

有机硅化合物在有机合成中具有广泛的应用.它可以经过简单的反应转化为一系列的功能性的化合物.铜催化的不饱和化合物的共轭硅化反应是一种重要的合成有机硅化合物的方法.综述了铜催化的不饱和化合物的共轭硅化反应的发展过程及用于硅化反应的硅试剂的发展历程,重点总结了近些年的相关报道,尤其是不对称共轭硅化反应的进展.     

硝基烯类化合物在有机合成中的应用

本文总结了硝基烯类化合物在有机合成中的应用。硝基烯是用途广泛的合成子,易受到亲核试剂如碳负离子、亚磷酸酯等的进攻形成加成产物。它和碳负离子的加成产物可以视为羰基的极性转换(umpolung)试剂,是合成取代羰基化合物的有效方法,它也是良好的亲双烯体,易于发生Diels-Alder反应。     

芳甲基叠氮化合物与烯烃及其衍生物反应研究进展

芳甲基叠氮化合物(ArCH_2N_3)可以为有机反应提供氮源,是一种性质稳定、合成简单的试剂,在有机合成化学领域被广泛应用.综述了最近五年来芳甲基叠氮化合物与烯烃在有机合成反应中的最新研究进展.分别叙述了芳甲基叠氮化合物在有机反应中与烯烃及其衍生物的底物适应范围和反应机理,为今后芳甲基叠氮化合物与烯烃类化合物的反应在有机合成中的应用提供参考.     

低价钒试剂促进的有机反应及其在有机合成中的应用

综述了近年来低价钒试剂促进的有机反应及其在有机合成中的应用。重点讨论了低价钒试剂促进下的碳-碳键的形成反应，如卤代烃的还原偶联、醛(酮)的还原偶联、羰基化合物的脱氧烷基化及脱氧偶联反应等。另外，还介绍了催化量的低价钒度剂在促进有机反应方面的应用。     

碘化1-甲基-2-异丙基(或丙基)-3-苯磺酰基咪唑啉的合成及基团转移反应

合成了新的四氢叶酸辅酶(THF)模型化合物碘化1-甲基-2-异丙基-3-苯磺酰基咪唑啉(5a)和碘化1-甲基-2-丙基-3-苯磺酰基咪唑啉(5b),研究了其反应性能.结果表明,化合物5与双官能团亲核体邻苯二胺或邻氨基苯酚反应,完全转移了4个碳的异丁基和正丁基单元,基于此探索了合成2-取代苯并咪唑及2-取代苯并唑的新方法;化合物5a与单官能团亲核体胺类反应部分转移了4个碳的异丁基单元,生成不同基团取代的N,N,N'-三取代乙二胺盐;化合物5a在Na BH4作用下可发生还原反应,在Na OH水溶液中可发生水解反应,也可与碳负离子基团(硝基甲基负离子或二腈基甲基负离子)发生亲核加成反应,生成了3类不同基团取代的N,N,N'-三取代乙二胺衍生物,探索了此类化合物的简易合成方法.这些反应模拟了四氢叶酸辅酶在生物体内转移一碳单元的功能,并将其扩展到4个碳原子单元,获得了可应用于有机合成的新方法和新试剂.     

有机碳负离子

在有机合成反应中,像某些反应中游离基中间体、互变异构、重排反应、取代反应,以及利用碳负离子进行的烷基化、芳基化、酰基化、共轭加成、与羰基和腈的加成、氧化等反应都与碳负离子有关。碳负离子表示在有机化合物的碳原子上带有负性电荷,此负性电荷的强弱与该化合物的结构和取代基有直接关系,若带有正性基团或金属阳离子及共轭键时,由于诱导效应使碳上的负性电荷减弱,反之可以使负性电荷增强。     

苯并咪唑盐与胺类化合物的加成-水解反应研究

四氢叶酸辅酶在生物体内的生物合成过程中的作用是转移不同氧化态的一碳单元.本课题组曾首次提出并报道了苯并咪唑盐作为四氢叶酸辅酶的模型化合物,并研究了该模型化合物与多种格利雅试剂和丙二酸二乙酯碳负离子等反应,实现了一碳单元的转移反应,为许多醛、酮和β-羰基酸等有机化合物提供了仿生合成新方法[1,2].本文对苯并咪唑盐与亲核试剂胺类化合物的加成-水解反应进行了研究,提出了苯并咪唑盐的另一种新反应,为一些酰胺类化合物提供了一种未见文献报道的重要仿生合成新方法.     

环丙烷与不饱和化合物发生[3+2]扩环反应的研究进展

由于具有较强的环张力,环丙烷能够与多种不饱和化合物发生[3+2]扩环反应构建五元碳环或五元杂环骨架结构.这些五元环化合物是许多药物、天然产物和生物活性分子的核心结构,同时也是一类重要的有机反应中间体,在医药、农业、化工、有机合成等领域具有十分广泛的用途.近年来,许多化学研究者以环丙烷作为三碳合成子,构建了结构复杂的五元碳环和五元杂环结构,促进了环丙烷领域的快速发展.对近十年来烯烃、醛酮、腈等含有不饱和键的化合物与环丙烷发生的[3+2]扩环反应进行了综述,并对该领域的发展方向进行了展望.     

Stereospecific Construction of Chiral Tertiary and Quaternary Carbon by Nucleophilic Cyclopropanation with Bis(iodozincio)methane

The reaction of a ketone having a leaving group at the α‐position, such as α,β‐epoxy ketone or α‐sulfonyloxy ketone, with bis(iodozincio)methane affords a zinc alkoxide of cyclopropanol. The reaction proceeds by nucleophilic addition of the dizinc to the carbonyl group and a sequential intramolecular nucleophilic substitution of the introduced iodozinciomethyl group to the adjacent electrophilic carbon that has a leaving group. When an optically active α,β‐epoxy ketone or α‐sulfonyloxy ketone is treated with the dizinc, a zinc alkoxide of cyclopropanol having a chiral tertiary or quaternary carbon in the cyclopropane ring is obtained, and the obtained zinc alkoxide of cyclopropanol acts as a chiral homoenolate. When it is treated with an electrophile in the presence of copper cyanide, it gives an optically active α‐tertiary or ‐quaternary ketone that retains high optical purity.     

Reexamination of the traditional Baylis-Hillman reaction

In the Baylis-Hillman reaction of arylaldehydes with methyl vinyl ketone (MVK), we found that, besides the normal Baylis-Hillman adduct 1, the diadduct 2 can also be formed at the same time and the yield of 2 can reach to 55% if increasing the amount of methyl vinyl ketone. But for ethyl vinyl ketone (EVK), methyl acrylate or acrylonitrile, only the normal Baylis-Hillman adduct 4, 7 or 8 was obtained, respectively. The substituent's effects and Lewis base effects were also examined and a plausible reaction mechanism was proposed for the formation of 2.     

The synthesis of angular methyl substituted bicyclic enones via a unique regioselective enamine annulation reaction

Enamines of 2,4,4-trimethylcyclopentanone 5 and of 2,5,5-trimethylcyclohexanone 14 react with methyl vinyl ketone to afford the bicyclic enones 9 and 15 in yields up to 70%. The formation of these products bearing an angular Me group is the result of an anomalous enamine Robinson annulation reaction, due to an alkylation of the enamine in the first step at its most substituted α-position. The effect of substitution in the α- and β′-position in the cycloalkanone, its ringsize, the structure of the Michael acceptor (alkyl vinyl ketone) was illustrated in reactions of the enamines of 2,5-dimethylcyclohexanone 22, carvomenthone 19, menthone 26, dihydrocarvone 28 and tetrahydroeucarvone 32 with methyl- and/or ethyl vinyl ketone.     

The first total synthesis and structural determination of epi-cochlioquinone A

The first total synthesis of epi-cochlioquinone A has been achieved in a highly convergent manner via [3+3] cycloaddition of catechol 2 and oxadecalin 3 as the key reaction. The synthesis of the catechol segment, possessing the side chain with multi stereogenic centers, features the asymmetric vinylogous Mukaiyama aldol reaction, the stereoselective conjugate addition to the nitroalkene, the stereospecific nitro-Dieckmann condensation, and the transformation of 6-nitrocyclohex-2-enone into catechol 2, using two new methodologies, such as (i) the hydrogen-transfer reaction to o-aminophenol and the subsequent auto-redox-catalysis to catechol and (ii) the direct oxidation of 6-nitrocyclohex-2-enone to o-quinone and the subsequent reduction. The oxadecalin segment was synthesized from a glycosyl cyanide by the [3+3] annulation with a ketone and an acetoacetate. These segments were connected by the [3+3] cyclization, and the resulting tetracyclic compound was subjected to a specific oxidation of the protected hydroquinone to provide epi-cochlioquinone A.     

Synthese de 2h-pyrroles et de pyrroles: action de carbanions sur des 2H-azirines ou des sels de N,N,N-trimethylhydrazonium

Dimsyl sodium reacts with 2H-azirines 2 to give amino ethylenic sulfoxide 5E. The same reaction is observed from N,N,N-trimethylhydrazonium salt 1 using an excess of dimsylsodium. Carbanions of ketone or nitrile react with 2H-azirine or N,N,N-trimethylhydrazonium to produce 2H-pyrroles 6–13, 20 or pyrroles 18, 19. This reaction is the most convenient general route to 2H-pyrroles.     

Coumarinyl aldehyde as a Michael acceptor type of colorimetric and fluorescent probe for cyanide in water

A simple aldehyde-functionalized coumarin (1) was utilized as a doubly activated Michael acceptor type of chemodosimeter for cyanide in water. The probe has shown a selective and sensitive response to the cyanide anion over other various anions through the Michael addition reaction of the cyanide to 1. When cyanide anions were added, the prominent color changes as well as fluorescence changes of 1 were observed so that millimolar concentrations of cyanides were detectable by the naked eye.     

1,2,3-Triazole as a safer and practical substitute for cyanide in the Bruylants reaction for the synthesis of tertiary amines containing tertiary alkyl or aryl groups

Tertiary amines containing tertiary alkyl or aryl groups were synthesized by the reaction of a ketone with an amine and 1,2,3-triazole followed by substitution of the triazole adduct with a Grignard reagent. Thus, 1,2,3-triazole serves as a safer and practical alternative to cyanide in the Bruylants reaction.     

Doubly activated coumarin as a colorimetric and fluorescent chemodosimeter for cyanide

A new α,β-unsaturated nitro group and coumarin conjugate-based fluorescent chemodosimeter 1 was developed for the selective detection of cyanide anions. The chemodosimeter has shown a selective and sensitive response to cyanide anions over other various anions through a nucleophilic aromatic substitution reaction of the cyanide to 1. When cyanide anions were added, the enhanced fluorescence intensity as well as the color changes of 1 was observed so that micromolar concentrations of cyanides were detectable by the naked eye.     

Synthesis and absolute configuration of (S)-(+)-chichimol ketone: the defensive secretion of walking stick Agathemera elegans

The first enantioselective synthesis of chichimol ketone (4-methyl-1-hepten-3-one) is described and the absolute configuration of the main semiochemical compound is determined as having an (S)-configuration. The synthesis features the use of a ruthenium catalytic asymmetric hydrogenation reaction to introduce chirality into acid 2. The synthetic chichimol ketone (S)-1 displayed a specific rotation that was in accordance with that of the natural product, thereby supporting the (S) configuration for natural chichimol ketone. To assure the correct stereochemical assignment, (S)-1 was converted in the known ketone (S)-5: the main alarm pheromone of the ant Atta texana that is 400 times more active than its (R)-enantiomers.     

Nucleophilic Cyclopropanation Reaction with Bis(iodozincio)methane by 1,4‐Addition to α,β‐Unsaturated Carbonyl Compounds

Treatment of α,β‐unsaturated ketones with an electrophilic site at the γ‐position in the presence of trimethylsilyl cyanide with bis(iodozincio)methane afforded the (Z)‐silyl enol ether of the β‐cyclopropyl substituted ketone in good yields. The reaction proceeds by 1,4‐addition to form an enolate, and its sequential intramolecular nucleophilic attack to an adjacent electrophilic site. The reaction of γ‐ethoxycarbonyl‐α,β‐unsaturated ketone and bis(iodozincio)methane in the presence of trimethylsilyl cyanide afforded 1‐ethoxy‐1‐trimethylsiloxycyclopropane derivatives, which can be regarded as the homoenolate equivalent. Additionally, reaction of the obtained homoenolate equivalents with imines give 1‐(E)‐alkenyl‐2‐(1‐aminoalkyl)alkanols diastereoselectively.