We gratefully acknowledge the Swedish Research Council Formas for generous financial support.

甲基-6-氧代-3,4,6- triphenylhexanoate 1.革兰氏规模合成<ol><li>干1-乙基-3-甲基咪唑鎓乙酸盐（EMIMAc）在10毫巴，40℃下1小时，在旋转蒸发器的圆底烧瓶中。 </li><li>添加2.1克干燥EMIMAc和1.0克1,3-二苯基-2-丙烯-1-酮向100毫升圆底烧瓶配备有磁力搅拌器。 </li><li>添加2.019毫升甲醇和2.3克肉桂烧瓶中。 </li><li>在室温（22℃）搅拌1分钟溶解在60毫升二氯甲烷的混合物中。 </li><li>接着添加0.37 ml的1.8二氮杂二环[5.4.0]十一-7-烯（DBU）到搅拌的混合物（步骤1.4）和帽的圆底烧瓶中。 </li><li>搅拌，在500rpm在室温（22℃）的速度一磁力搅拌棒。 </li><li>检查用 1 H-NMR。24查找在7.8 ppm的区域中的查耳酮的双键消失反应完成。 </li><li>当该反应达到<html>完成除去挥发旋转蒸发器上在10毫巴，20℃下进行15分钟。 </li><li>加入50毫升甲醇向残余物通过有磁性搅拌棒搅拌以溶解EMIMAc。 </li><li>通过用磁力搅拌棒搅拌下剧烈在750 rpm的速度为30分钟，除去从烧瓶壁上的固体。如果有必要，用刮刀从墙上去除剩余的固体。 </li><li>过滤器玻璃料（孔径3）的混合物。 </li><li>用另外20ml甲醇洗。如果回收EMIMAc的期望蒸发甲醇滤液。 （步骤2.1）。 </li><li>仍然在玻璃料上，轻轻地划分滤饼（从步骤1.11）成较小的块用刮勺和经由粉末漏斗转移到固体预称重的圆底烧瓶中，并在真空下干燥固体。 </li><li>称量烧瓶并计算产率。 </li><li>由1 H NMR（步骤1.7）分析产物。有报道光谱进行比较。24 </li></ol>EMIMAc的标题"&gt; 2。循环<ol><li>在10毫巴减压除去从甲醇混合物（来自步骤1.12）挥发物，在40℃下30分钟。 </li><li> 通过 1 H NMR和13 C-NMR分析所得的油，以检查EMIMAc存在。24 </li><li>使用回收EMIMAc从步骤1.2开始。 </li></ol> 3.凝胶<ol><li>储备溶液的制备<ol><li>加入200毫克甲基-6-氧代-3,4,6- triphenylhexanoate（从步骤1.15的产物）和磁搅拌棒至小瓶的。加入2.0毫升二氯甲烷中，以溶解酮酯。搅拌，直到一切都已经解散。 </li></ol></li><li>凝胶<ol><li>加入50毫升庚烷，以500毫升烧杯中。添加1.5 ml的储备溶液的庚烷。搅拌迅速，以确保充分混合，静置而不直至凝胶化发生在环境温度下搅拌。 </li></ol></li></ol>

<ol>
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The authors have nothing to disclose.

基于由酮酯3的X射线分析和对所提出的Bode和同事30的机械调查确定反 -构型的下述反应路径建议（图5）。白细胞介素脱质子产生NHC种;所述NHC反应与不饱和醛形成布瑞斯罗夫中间体I中布瑞斯罗夫中间和在跨安息香反应的查耳酮反应形成二烯二。中级II经过转乘船过渡态（TS）的氧Cope重排，设置防取向的手性中心III。互变异构之后，酰基氮鎓IV与甲醇反应来交付产品?...

<img alt="TOC 1" src="/files/ftp_upload/53213/53213TOC.jpg" /> （以上）的1,6-酮酯三组分合成:一类新的低分子量胶凝剂。 离子液体（离子液体）具有高稳定性，低挥发性，不可燃性，并因此呈现关注，因为安全的反应介质和理想的溶剂进行回收。1-3二烷基咪唑鎓是一个特定类型的离子液体，在碱的存在下可以去质子化，以使一个N-杂环卡宾（NHC）。4在有机催化的领域中，的NHCs，根据不同的反应路径操作时，已经被广泛的使用在广泛的通用反应。5-11 尽管如此，ILS和CC键formin之间的连接摹NHC催化相对未开发的。尽管如此，从的NHCs离子液体衍生已经报道了催化CC键形成反应，如苯偶姻缩合和施德达反应。12-22。例如，Davis等人已经表明，从N-烷基thiazoliums衍生离子液体作为在预催化剂形成苯甲醛安息香12 最近，Chen和同事扩展使用基于IL咪唑这个概念，1-乙基-3-甲基咪唑鎓乙酸盐（EMIMAc），对5-羟甲基糠醛（HMF）执行安息香缩合以生成5,5&#39; -二（羟甲基）furoin（DHMF）。23由于离子液体可以买到，报价产生NHC的的一种廉价的方式，我们有兴趣在研究什么其他类型的反应，离子液体可以执行。为此，我们发现，二烷基咪唑鎓可有效用作在正规共轭additi预催化剂上的不饱和醛以查耳酮（图1），得到1,6-酮酯。最有效的IL，EMIMAc，促进肉桂醛和查尔之间的高立体选择性反应。发生反应以高偏爱反 -非对映和1,6-酮酯可以分离在产率高达92％。24,25,26 <img alt="图1" src="/files/ftp_upload/53213/53213fig1.jpg" /> 图1:IL-介导的三组分，立体选择性加成肉桂醛以查耳酮。

<table><tbody><tr><td>1-ethyl-3-methyl imidazolium acetate</td><td>Aldrich</td><td>51053-100G-F</td><td>Produced by BASF &amp;ge;90%, dried on a rotary evaporated before use (10 mBar, 40 &amp;deg;C, 1 hr)&lt;br/&gt; CAS NUMBER: 143314-17-4</td></tr><tr><td>1,3-diphenyl-2-propen-1-one</td><td>Aldrich</td><td>11970-100G</td><td>98.0%&lt;br/&gt; CAS NUMBER: 94-41-7</td></tr><tr><td>trans-cinnamaldehyde&amp;nbsp;</td><td>Aldrich</td><td>C80687-25G</td><td>99%, stored under nitrogen prior to use&lt;br/&gt; CAS NUMBER: 14371-10-9</td></tr><tr><td>1,8-Diazobicyclo[5.4.0]undec-7-ene</td><td>Aldrich</td><td>139009-25G</td><td>98%&lt;br/&gt; CAS NUMBER: 6674-22-2</td></tr><tr><td>Methanol</td><td>Sigma-Aldrich</td><td>32213N-2.5L</td><td>puriss. P.a., ACS reagent, reag. ISO, reag. Ph. Eur. &amp;ge;99.8% (GC)&lt;br/&gt; CAS NUMBER: 67-56-1</td></tr><tr><td>Dichloromethane</td><td>Fischer Chemical</td><td>D/1852/17X</td><td>Analytic reagent grade, stabilized with amylene&lt;br/&gt; CAS NUMBER: 9/2/1975</td></tr><tr><td>n-Heptane</td><td>Fischer Chemical</td><td>H/0160/17X</td><td>Analytic reagent grade&lt;br/&gt; CAS NUMBER: 142-82-5</td></tr></tbody></table>

highly stereoselective synthesis of 1,6-ketoesters mediated by ionic liquids: a three-component reaction enabling rapid access to a new class of low molecular weight gelators

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form catalytically active N-Heterocyclic Carbenes (NHCs). Here we have used ILs as precatalysts in the addition of &#945;,&#946;-unsaturated aldehydes to chalcones to form 1,6-ketoesters, incorporating an anti-diphenyl moiety in a highly stereoselective fashion. The reaction has a broad substrate scope and several functional groups and heteroaromatics can be integrated into the ketoester backbone in generally good yields with maintained stereoselectivity. The reaction protocol is robust and scalable. The starting materials are inexpensive and the products can be obtained after simple filtration, avoiding solvent-demanding chromatography. Furthermore, the IL can be recycled up to 5 times without any loss of reactivity. Moreover, the 1,6-ketoester end product is a potent gelator in several hydrocarbon based solvents. The method enables rapid access to and evaluation of a new class of low molecular weight gelators (LMWGs) from recyclable and inexpensive starting materials.

如上述例举EMIMAc充当在正规共轭加成α，β不饱和醛与查耳酮一个前段催化剂。其它市售咪唑鎓基的离子液体，例如1-乙基-3-甲基咪唑氯化物（EMIMCl）和1-丁基-3-甲基咪唑氯化物（BMIMCl）也进行了研究，然而，这些反应进行较低的产率，表明乙酸根阴离子可以是为反应性（ 表1，进入1-3）很重要。27,28 * *阴离子该反应中的作用是在目前还不清楚?...

Watch this Scientific Journal Video about Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

Ionic liquids (ILs) mediate fast, simple and cheap access to 1,6-ketoesters in high diastereoselectivities and good yields. The reaction protocol is robust and the 1,6-ketoesters can be obtained in gram scale after a simple filtration protocol. Moreover, the 1,6-ketoesters are potent gelators in hydrocarbon solvents.

1,6-酮酯高立体选择性合成离子液体介导:三组分反应启用快速进入低分子量胶凝剂的新型类

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form ...

highly-stereoselective-synthesis-16-ketoesters-mediated-ionic-liquids

Research

JoVE Journal

Chemistry

8.7K 次观看.  Chalmers University of Technology. Ionic liquids (ILs) mediate fast, simple and cheap access to 1,6-ketoesters in high diastereoselectivities and good yields. The reaction protocol is robust and the 1,6-ketoesters can be obtained in gram scale after a simple filtration protocol. Moreover, the 1,6-ketoesters are potent gelators in hydrocarbon solvents. 

视频: Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer by generating a charged structure provides an opportunity to use extraction as a simple purification technique. By combining the use of a miscible organic solvent with saturated sodium bisulfite, aldehydes and reactive ketones can be successfully transformed into charged bisulfite adducts that can then be separated from other organic components of a mixture by the introduction of an immiscible organic layer. Here, we describe a simple protocol for the removal of aldehydes, including sterically-hindered neopentyl aldehydes and some ketones, from chemical mixtures. Ketones can be separated if they are sterically unhindered cyclic or methyl ketones. For aliphatic aldehydes and ketones, dimethylformamide is used as the miscible solvent to improve removal rates. The bisulfite addition reaction can be reversed by basification of the aqueous layer, allowing for the re-isolation of the reactive carbonyl component of a mixture.

Here, we present a protocol to remove aldehydes and reactive ketones from mixtures by a liquid-liquid extraction protocol directly with saturated sodium bisulfite in a miscible solvent. This combined protocol is rapid and facile to perform. The aldehyde or ketone can be re-isolated by the basification of the aqueous layer.

用亚硫酸氢萃取协议分离混合物中的醛和反应性酮

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer ...

科研

化学

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. Recently, we have developed a two-step strategy for ketone enolate umpolung that has enabled the development of methods for chlorination, azidation, and amination using azoles. In addition, we have developed C-C bond&#8211;forming arylation and allylation reactions. At the heart of these methods is the preparation of the intermediate and highly reactive enolonium species prior to addition of a reactive nucleophile. This strategy is thus reminiscent of the preparation and use of metal enolates in classical synthetic chemistry. This strategy allows the use of nucleophiles that would otherwise be incompatible with the strongly oxidizing hypervalent iodine reagents. In this paper we present a detailed protocol for chlorination, azidation, N-heteroarylation, arylation, and allylation. The products include motifs prevalent in medicinally active products. This article will greatly assist others in using these methods.

A two step one-pot protocol for the umpolung of ketone enolates to enolonium species and addition of a nucleophile to the &#945;-position is described. Nucleophiles include chloride, azide, azoles, allyl-silanes, and aromatic compounds.

Enolonium 种极性转换酮功能化的两步协议

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. ...

Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes

We present the chemoselective synthesis of 1-(iodoethynyl)-4-methylbenzene, 1-(1,2-diiodovinyl)-4-methylbenzene, and 1-methyl-4-(1,2,2-triiodovinyl)benzene as representative examples for the practical chemoselective preparation of 1-iodoalkynes, 1,2-diiodoalkenes, and 1,1,2-triiodoalkenes from the chemoselective iodination of terminal alkynes mediated by hypervalent-iodine reagents. The chemoselectivity was confirmed by using p-tolylethyne as a model substrate to screen a variety of iodine sources and/or the hypervalent-iodine reagents. A combination of tetrabutylammonium iodide (TBAI) and (diacetoxyiodo)benzene (PIDA) selectively generates 1-iodoalkynes, while a combination of KI and PIDA generates 1,2-diiodoalkenes. A one-pot synthesis based on both TBAI-PIDA and KI-PIDA yields the corresponding 1,1,2-triiodoalkenes. These protocols were subsequently applied to the synthesis of synthetically important aromatic and aliphatic 1-iodoalkynes, 1,2-diiodoalkenes, and 1,1,2-triiodoalkenes, which were obtained in good yield with excellent chemoselectivity.

Herein, detailed protocols for the oxidative iodination of terminal alkynes using hypervalent-iodine reagents are presented, which chemoselectively afford 1-iodoalkynes, 1,2-diiodoalkenes, and 1,1,2-triiodoalkenes.

基于末端碘氧化炔烃的 1-Iodoalkynes、12-Diiodoalkenes、11、2 Triiodoalkenes 的 Chemoselective 制备

We present the chemoselective synthesis of 1-(iodoethynyl)-4-methylbenzene, 1-(1,2-diiodovinyl)-4-methylbenzene, and ...

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the reaction is commonly performed using chlorinated or amide solvent systems, which are hazardous to human health and the environment. Our methodology utilizes acetonitrile as a greener and less hazardous solvent system. This protocol exhibits rates and yields that are comparable to traditional solvent systems and employs an extraction and wash sequence that eliminates the need for the purification of the ester product via column chromatography. This general method can be used to couple a variety of carboxylic acids with 1&#176; and 2&#176; aliphatic alcohols, benzylic and allylic alcohols, and phenols to obtain pure esters in high yields. The goal of the protocol detailed here is to provide a greener alternative to a common esterification reaction, which could serve useful for ester synthesis in both academic and industrial applications.

A modified Steglich esterification reaction was used to synthesize a small library of ester derivatives with primary and secondary alcohols. The methodology uses a non-halogenated and greener solvent, acetonitrile, and enables product isolation in high yields without the need for chromatographic purification.

乙腈绿色 Steglich 酯化合成酯的研究

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the ...

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of &#945;-Imino &#947;-Lactones and Alkylidene Pyrazolones

Bispirocyclic scaffolds are one of the important structural subunits in many natural products that exhibit diverse and attractive biological activities. Recently, we have developed an efficient organocatalytic strategy, which provides facile access to a variety of enantiomerically enriched bispiro[&#947;-butyrolactone-pyrrolidin-4,4&#39;-pyrazolone] skeletons. In this paper, we demonstrate a detailed protocol for the asymmetric synthesis of drug-like bispirocyclic compounds with two spirocyclic carbon centers via an organocatyltic 1,3-dipolar cycloaddition reaction. Spirocyclization synthons &#945;-imino &#947;-lactones and alkylidene pyrazolones are prepared first, which are then subjected to a cycloaddition reaction in the presence of a bifunctional squaramide organocatalyst to afford the desired bispirocycles in high yields and excellent stereoselectivities. Chiral high-performance liquid chromatography (HPLC) is carried out to determine the enantiomeric purity of the products, and the d.r. value is examined by proton nuclear magnetic resonance (1H NMR). The absolute configuration of the product is assigned according to an X-ray crystallographic analysis. This synthetic strategy allows scientists to prepare a diversity of bispirocyclic scaffolds in high yields and excellent diastereo- and enantioselectivities.

Enantiomerically enriched bispiro[&#947;-butyrolactone-pyrrolidin-4,4&#39;-pyrazolone] skeletons are asymmetrically synthesized through a simple organocatalytic 1,3-dipolar cycloaddition reaction.

α-伊米诺γ-乳胶酮和阿基地利酮吡唑酮有机催化环加花法高效构建药物样双环脚手架

Bispirocyclic scaffolds are one of the important structural subunits in many natural products that exhibit diverse and attractive biological activities. ...

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the preparation of all-carbon quaternary centers. Though conjugate additions of organometallic reagents are typically performed utilizing highly reactive organolithium or Grignard reagents, organozinc reagents have garnered attention for their enhanced chemoselectivity and mild reactivity. Despite numerous recent advances with more reactive diorganozinc and mixed diorganozinc reagents, the generation of all-carbon quaternary centers via the conjugate addition of functionalized monoorganozinc reagents remains a challenge. This protocol details a convenient and mild &#8220;one-pot&#8221; preparation and copper mediated conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to afford a broad scope of all-carbon quaternary centers in generally excellent yield and diastereoselectivity. Key to the development of this technology is the utilization of DMA as a reaction solvent with TMSCl as a Lewis acid. Notable advantages to this methodology include the operational simplicity of the organozinc reagent preparation afforded by the utilization of DMA as a solvent, as well as an efficient conjugate addition mediated by various Cu(I) and Cu(II) salts. Moreover, an intermediate silyl enol ether can be isolated utilizing a modified workup procedure. The substrate scope is limited to cyclic unsaturated ketones, and the conjugate addition is impeded by stabilized (e.g., allyl, enolate, homoenolate) and sterically encumbered (e.g., neopentyl, o-aryl) monoorganozinc reagents. Conjugate additions to five- and seven-membered rings were effective, albeit in lower yields compared with six-membered ring substrates.

A simple and practical protocol for the efficient conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to furnish all-carbon quaternary centers was developed.

功能化单有机硼化合物共轭法高效合成全碳第四纪中心

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the ...

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products and notably to generate chiral carbon centers. The crucial first step consists in the selective double hydroboration of CO2 catalyzed by an iron hydride complex. The product obtained with this 4 e- reduction is a rare bis(boryl)acetal, compound 1, which is subjected in situ to three different reactions in a second step. The first reaction concerns a condensation reaction with (diisopropyl)phenylamine affording the corresponding imine 2. In the second and third reaction, intermediate 1 reacts with triazol-5-ylidene (Enders&#39; carbene) to afford compounds 3 or 4, depending on the reaction conditions. In both compounds, C-C bonds are formed, and chiral centers are generated from CO2 as the only source of carbon. Compound 4 exhibits two chiral centers obtained in a diastereoselective manner in a formose-type mechanism. We proved that the remaining boryl fragment plays a key role in this unprecedented stereocontrol. The interest of the method stands on the reactive and versatile nature of 1, giving rise to various complex molecules from a single intermediate. The complexity of a two-step method is compensated by the overall short reaction time (2 h for the larger reaction time), and mild reaction conditions (25 &#176;C to 80 &#176;C and 1 to 3 atm of CO2).

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

CO2 transformations are conducted in a one-pot two-step procedure for the synthesis of complex molecules. The selective 4 e- reduction of CO2 with a hydroborane reductant affords a reactive and versatile bis(boryl)acetal intermediate which is subsequently involved in condensation reaction or carbene-mediated C-C coupling generation.

多功能 CO2转化为复杂产品:单罐两步战略

CO2 transformations using a one-pot two-step method are presented herein. The purpose of the method is to give access to a variety of value-added products ...

Organocatalysis

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate the concept of organocatalysis by illustrating the proper setup of a reaction that utilizes enamine catalysis. Organocatalysis is a form of catalysis that uses substoichiometric amounts of small organic molecules to accelerate reactions. This type of catalysis is complementary to other forms of catalysis such as transition metal or biocatalysis. Transition metal catalysis involves transition metals as catalysts and biocatalysis uses enzymes as catalysts. Some advantages of organocatalysis include the low toxicity and cost of the organocatalysts in comparison to many metal catalysts. In addition, most organocatalysts are not sensitive to air and moisture, unlike metal catalysts. In contrast to enzymes found in living organisms, the small molecules that act as organocatalysts are typically easy to access. Furthermore, organocatalysis offers complementary and new reactivity not observed with other forms of catalysis.

Organocatalysis: Principles and Applications

催化

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate the concept of ...

教育

JoVE Science Education

有机化学 (2)

&alpha;-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview

The pinacol and McMurry reactions involve the reductive coupling of ketones or aldehydes. Similarly, the bimolecular reductive coupling of two ester molecules in the presence of sodium metal in an aprotic solvent yields an &#945;-hydroxy ketone product. The &#945;-hydroxy ketone is also called acyloin, so the reaction is referred to as &#8216;acyloin condensation.&#8217;
<img alt="Figure1" src="/files/ftp_upload/12908/12908_PT_Figure_1.svg" style="text-align: center; height: 65px;" />
In the acyloin condensation reaction, esters are converted to ketyls, which undergo radical dimerization to form an unstable tetrahedral intermediate. Further, this intermediate collapses to give a 1,2-diketone intermediate. The 1,2-diketones are comparatively more reactive than ketones towards electrophiles and reducing agents because of lower &#960;* energy. Consequently, two electrons sequentially transfer to the 1,2-diketone to form an enediolate. Lastly, the enediolate intermediate is quenched with acid to yield an &#945;-hydroxy ketone with a good yield.
Often some by-products are obtained alongside the major product because of the reactivity of nucleophilic enediolate. To overcome the side reactions and improve the yield of an acyloin, trimethylsilyl chloride is used to silylate the enediolate. This results in a bis-silyl ether, further hydrolyzed with aqueous acid to give &#945;-hydroxy ketones.

&amp;#945;-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview

通过酯的还原偶联得到 α-羟基酮:Acyloin 缩合概述

The pinacol and McMurry reactions involve the reductive coupling of ketones or aldehydes. Similarly, the bimolecular reductive coupling of two ester ...

JoVE Core

有机化学

Unit 1

Radical Chemistry

关键术语与概念

&alpha;-Alkylation of Ketones via Enolate Ions

Ketones with &alpha; protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the &#945; carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the &#945;&nbsp;carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the strong interaction of the positive counterpart of the base with the anionic oxygen, which restricts the approaching electrophile, making the reaction less favorable. Also, the product obtained through C-attack is more stable than that obtained through O-&NoBreak;attack, as the stronger C=O &#960; bond is retained in the former, whereas a weaker C=C &#960; bond is preserved in the latter.
A subsequent reaction of the enolate with electrophiles such as alkyl halides produces an &#945;-alkylated ketone via the SN2 pathway. The &#945;-alkylation of ketones is achieved with the halides of primary alkyl, benzyl, and allylic groups. With secondary and tertiary alkyl halides, elimination predominates over substitution.

1,6-酮酯高立体选择性合成离子液体介导:三组分反应启用快速进入低分子量胶凝剂的新型类

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