Name: 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
Uploaded: 2015-11-27T15:00:00.000+00:00
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Description: 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

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메틸 -6- 옥소 -3,4,6- triphenylhexanoate 1. 그램 규모의 합성 <ol><li> 10 mbar에서, 1 시간 동안 40 ℃에서 회전 증발기에서 둥근 바닥 플라스크에 건조 1- 에틸 -3- 메틸이 미다 졸륨 아세테이트 (EMIMAc). </li><li> 건조 EMIMAc 2.1 g 및 1,3- 디 페닐 -2- 프로 펜 -1- 온 마그네틱 교반기가 구비 된 100 ㎖ 둥근 바닥 플라스크에 1.0 g을 추가한다. </li><li> 메탄올 2.019 mL의 플라스크에 신남 2.3 g을 넣고. </li><li> 실온 (22 ℃)에서 1 분 동안 교반하여 디클로로 메탄 60 mL의 혼합물에 용해. </li><li> 그 후 0.37 mL의 1.8 디아 자비의 추가 [5.4.0] 운덱 -7- 엔, 교반 혼합한다 (단계 1.4) 및 둥근 바닥 플라스크를 캡핑 (DBU). </li><li> 상온 (22 ° C에서)에서 500 rpm의 속도에서 자기 교반 막대로 교반 하였다. </li><li> 1 H NMR. 7.8 ppm의 영역에서 칼콘의 이중 결합의 실종 24 표정으로 반응 종료를 확인합니다. </li><li> 반응물에 도달 할 때<html> 완성 10 밀리바, 15 분 동안 20 ℃에서 회전 증발기에서 휘발성 물질을 제거한다. </li><li> 자기 교반 막대로 교반 EMIMAc을 용해 잔사에 50㎖의 메탄올을 첨가한다. </li><li> 30 분 동안 750 rpm의 속도에서 자기 교반 막대로 격렬하게 교반하여 플라스크의 벽에서 고형물을 제거한다. 필요할 경우, 벽에서 남은 고형물을 제거하기 위해 주걱을 사용한다. </li><li> 프릿 (기공 크기 3)의 혼합물을 필터링합니다. </li><li> 메탄올의 추가 20 ㎖로 세척. EMIMAc 재활용이 요구되는 경우 메탄올 성 여액을 증발시켰다. (2.1 단계). </li><li> 여전히 프릿에 부드럽게 주걱 작은 조각으로 (단계 1.11)에서 필터 케이크를 나누어 미리 칭량 둥근 바닥 플라스크에 분말 깔때기를 통해 고체를 전송하고, 진공하에 고체를 건조. </li><li> 플라스크의 무게를 측정하고 수율을 계산한다. </li><li> 1 H NMR (스텝 1.7)에 의해 생성물을 분석한다. 보고 스펙트럼 비교. (24) </li></ol>EMIMAc의 제목 &quot;&gt; 2. 재활용 <ol><li> 30 분 동안 40 ° C에서 10 밀리바의 감압 (단계 1.12)에서 메탄올 혼합물로부터 휘발성 물질을 제거한다. </li><li> EMIMAc가 있는지 확인하기 위해 1 시간 NMR 및 13 C NMR에 의해 생성 된 오일을 분석한다. (24) </li><li> 재활용 EMIMAc 단계 1.2부터 사용합니다. </li></ol> 3. 겔화 <ol><li> 원액의 제조 <ol><li> 메틸 -6- 옥소 -3,4,6- triphenylhexanoate (단계 1.15에서 제품) 및 유리 병에 자기 교반 막대의 200 mg을 추가합니다. 케토 에스테르를 용해 2.0 ml의 디클로로 메탄을 추가합니다. 모든 때까지 저어은 해산했다. </li></ol></li><li> 동결 <ol><li> 500㎖의 비이커에 헵탄 50 mL로 추가한다. 헵탄에 원액의 1.5 ML을 추가합니다. 적절한 혼합을 보장하고 겔화가 일어날 때까지 실온에서 교반없이 서 있도록 신속하게 교반한다. </li></ol></li></ol>

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The authors have nothing to disclose.

케토 에스테르 (3)의 X 선 분석 및 보데 및 동료 (30)에 의해 제안 된 기전 조사하여 결정 안티 배위에 기초하기 반응 경로는 (도 5)를 제안한다. IL의 탈 양성자는 NHC 종을 생성; NHC는 Breslow 중간 I. Breslow 중간체 형성하는 불포화 알데히드와 반응은 칼콘 디엔 II를 형성하도록 상호 벤조 반응에서 반응한다. 중급 II는 안티 지향 입체 센터 III를 설정, 보트 전이 상태 (TS)...

<img alt="TOC (1)" src="/files/ftp_upload/53213/53213TOC.jpg" /> (위) 1,6- ketoesters의 3 성분계 합성 : 저 분자량 젤 레이터의 새로운 클래스. 이온 성 액체 (ILS)의 높은 안정성, 낮은 휘발성, 비 - 가연성을 가지므로 재활용 안전한 반응 매체와 이상적인 용매로서 관심을 표현하고있다. 1-3 디 알킬 imidazoliums은 이온 성 액체의 특정 유형임을, 염기의 존재하에 , organocatalysis의 분야에서 N- 헤테로 카르 벤 (NHC). (4)을 렌더링하기 위해 탈 수있는, NHCs, 서로 다른 반응 경로에서 작동, 일반적인 반응의 넓은 범위에서 광범위하게 사용을 발견했다. 5-11 그럼에도 불구하고, 대한 IL 및 CC 결합 formin 사이의 연결G NHC-촉매는 상대적으로 미개척입니다. 그럼에도 불구하고, IL을으로부터 유도 NHCs 그러한 벤조 축합 STETTER 반응으로 형성 반응 CC 결합을 촉진하는 것으로보고되고있다. 예를 들어 12-22, 데이비스 외. N - 알킬 thiazoliums로부터 유도의 IL이있는 precatalysts 역할을 보여 주었다 벤즈알데히드로부터 형성 벤조. 12 최근 첸과 동료 IL 기반 졸리움을 사용하여 이러한 개념을 확장, 1- 에틸 -3- 메틸이 미다 졸륨 아세테이트 (EMIMAc) &#39;5,5 생성 5- hydroxymethylfurfural (HMF)에 벤조 축합을 수행하는 디 대한 IL 상업적으로 사용할 수 있으며, NHCs을 생성하는 저렴한 방법을 제공하는 점을 감안 (히드 록시 메틸) furoin (DHMF). (23), 우리는 반응에 대한 IL의 다른 유형 수행 할 수있는 것을 조사에 관심이 있었다. 이를 위해, 디 알킬 imidazoliums 효율적 공식 공액 additi에 precatalysts로서 사용될 수 있다는 것을 발견불포화 알데히드에 1,6- ketoesters을주는 칼콘 (그림 1)에. 가장 효율적인 IL, EMIMAc는 신남 및 칼콘 사이 높은 입체 선택적 반응을 촉진한다. 반응은 안티 -diastereomer에 대한 높은 선호도 발생 및 1,6- ketoesters은 최대 92 % 수율로 분리 할 수있다. 24,25,26 <img alt="그림 1" src="/files/ftp_upload/53213/53213fig1.jpg" /> 그림 1 : 세 가지 구성 요소, 칼콘에 신남의 입체 추가 IL-매개.

<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.

상기 예시 된 바와 같이, EMIMAc은 칼콘에 α, β 불포화 알데히드 공식 공액 또한 예비 촉매 역할을한다. 1- 에틸 -3- 메틸이 미다 졸륨 클로라이드 (EMIMCl) 및 1- 부틸 -3- 메틸이 미다 졸륨 클로라이드 (BMIMCl)와 같은 다른 시판 졸리움 계의 IL은 조사했다, 그러나, 아세테이트 음이온이있을 수 있음을 나타내는 낮은 수율로 진행 이들 반응 반응성 (표 1, 항목 1-3) 중요. 27, 28 *</s...

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.

이온 성 액체에 의해 매개 1,6- Ketoesters의 높은 입체 선택적 합성 : 저 분자량 젤 레이터의 새로운 클래스에 빠른 액세스를 가능하게하는 3 요소 반응

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

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JoVE Journal

Chemistry

8.8K 조회수.  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. 

비디오: 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.

알 데히드 류와 Ketones 반응 황산 추출 프로토콜을 사용 하 여 혼합물에서 분리

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

연구

화학

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 종 통해 Ketones의 Umpolung 기능화에 대 한 2 단계 프로토콜

&#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.

1-Iodoalkynes, 1, 2-Diiodoalkenes, 및 1,1,2 Triiodoalkenes 터미널 Alkynes의 산화 Iodination에 따라 Chemoselective 준비

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.

이기에 친 환 경적 Steglich 에스테 르 화를 통해 에스테 르의 합성

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-Imino γ-Lactones의 Organocatalytic Cycloadditions 및 Alkylidene Pyrazolones 통해 마약 같은 Bispirocyclic 장비의 효율적인 건설

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.

관 능 적 모노 아연 브로 미 데스의 결합체 첨가를 통한 전 탄소 4 급 센터의 효율적인 합성

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.

다재다능한CO2를 복합 제품으로 전환: 원포트 2단계 전략

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

오가노카타리시스

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

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유기 화학 II

&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

에스테르의 환원적 결합을 통한 α-하이드록시 케톤: 아실로인 응축 개요

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

JoVE Core

유기화학

Unit 1

Radical Chemistry

주요 용어 및 개념

&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.

이온 성 액체에 의해 매개 1,6- Ketoesters의 높은 입체 선택적 합성 : 저 분자량 젤 레이터의 새로운 클래스에 빠른 액세스를 가능하게하는 3 요소 반응

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