Name: one-pot microwave-assisted conversion of anomeric nitrate-esters to trichloroacetimidates
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Description: Watch this Scientific Journal Video about One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates at JoVE.com

作者要感谢范德比尔特大学和化学生物学研究所的资助。Mr. 伯克利埃利斯和 Prof. 是公认的高分辨率质谱分析。

1. 有代表性的微波辅助脱硝
<ol><li>将叠硝酸酯 (1.0 equiv, 0.2 摩尔) 放在8毫升的微波反应瓶中。反应的规模可以增加到几个摩尔, 而不会对反应进展产生任何不利影响。</li>
	<li>将叠-硝酸酯溶于20% 蒽醌丙酮 (0.1 米, 2.0 毫升)。将吡啶 (5.0 equiv, 0.08 毫升, 1.0 摩尔) 加入反应釜。将该反应容器盖在微波反应器腔内, 并将其置于微波炉辐照瓶中。</li>
	<li>照射解决方案在120° c 为15分钟, 搅拌和固定保持时间。保持时间表示辐照在指定温度和由此产生的压力下会发生多久。在2分钟的爬坡期内对报告的温度进行热反应。通过内置红外传感器监视温度。</li>
	<li>15分钟后, 用薄层层析 (TLC) 对反应混合物进行分析, 确定起动材料的消耗量。使用1:1 乙酸乙酯/hexanes 作为淋洗。<ol>
<li>用铈铵 molybate 染色法对薄层板进行可视化。反应物和产品的 rf会有所不同, 但还原酒精一般是0.05 到0.1 下 rf , 而不是反应剂。</li>
	</ol>
</li>
</ol>2. trichloroacetimidate 的形成
<ol><li>在开始的材料的完全消耗量以后, 蒸发溶剂到减少的容量使用航空公司。然后, 用 (二氯甲烷) CH2Cl2 (1.0 毫升) 稀释, 用注射器除去水层。一旦水层被去除, 冷却反应混合物到0° c 使用冰水浴。</li>
	<li>接下来, 添加 DBU (10 eq, 0.3 毫升, 1.9 摩尔) 和 22, 2-乙 (50 eq, 1.0 毫升, 10 摩尔) 的反应容器。这两种试剂都是多余的, 至少有1的碱基和1当量的 22, 2-乙是需要的。</li>
	<li>允许反应混合物在升温到环境温度时搅拌。通过薄层色谱法监测反应, 确定起始物料消耗量。<ol>
<li>使用1:1 乙酸乙酯/hexanes 作为淋洗。用铈铵 molybate 染色法对薄层板进行可视化。反应物和产品的 Rf会有所不同。</li>
	</ol>
</li>
	<li>在开始材料的完全消耗量以后, 转移反应混合物到回收瓶和集中混合物在真空在30° c。溶剂的蒸发会使原油呈淡黄色至褐色油。</li>
	<li>以 1.5 cm 色谱柱和1:4 乙酸乙酯/hexanes 为淋洗, 用硅胶柱层析法提纯粗品。imidate 的物理形态会因分子而异。</li>
</ol><img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56610/56610fig1v3.jpg"> 图 1.2-叠-1-硝酸酯的一锅转化为 2-叠-1-trichloroimidates 的代表性例子。<a href="//cloudflare.jove.com/files/ftp_upload/56610/56610fig1v3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

<ol>
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作者没有相互竞争的金融利益。

本教程中描述的协议提供了一种将硝酸酯转化为有用的、无功功能的方法。从更广泛的意义上说, 使用微波反应器来完成碳水化合物合成过程中的特定动作, 有可能使困难的转变变得轻便和例行。在本教程中, 我们的目标是演示如何在微波照射的情况下处理碳水化合物。
在父母反应的情况下, 以前的努力, 以实现脱硝通常依赖于强亲核试剂和延长反应时间。本文所描述的技术的?...

由于它们在分子生物学中无处不在, 碳水化合物一直是化学合成的长期目标。1,2,3在任何成功的合成运动的核心是正确部署糖基化反应, 以建立低聚糖链。4,5,6,7,8,9,10,11,12不奇怪的是, 有大量的方法来安装糖苷债券。13,14汤姆·柯尼希斯-克诺尔方法是已知最早的程序之一, 它涉及将糖氯化物或溴化物与酒精成分结合, 通常在重金属 (汞或银) 活化作用下。15相关的糖氟化物在1981年被醛集团首次作为捐赠者引入, 并因其热化学稳定性的提高而得到广泛应用。在反应谱的相反端的16是糖化, 它比其他卤化物的反应要多得多。增加的反应性伴随着增加的 stereocontrol, 特别是当形成α连接的寡糖。17除了 "haloglycosides" 外, thioglycosides 还发现了广泛的效用, 部分原因在于它们易于形成, 稳定性对大量的反应条件和活化亲试剂。18
上述方法的重点是将 anomeric 醇转化为 "氧", 即由受体分子中的酒精激活并最终取代的潜离组。Anomeric 氧活化, 如施密特学派所描述的, 重点是将 C1 氧本身转化为一个离群。19这种方法是最强大的, 广泛应用于化学糖基化反应。Trichloroacetimidate 捐赠者从还原糖和乙容易地准备, 在基地存在例如碳酸钾 (K2CO3) 或 18-环 [5.4. 0] undec-7-烯 (DBU)。这些物种, 然后激活使用刘易斯酸。20
最近, 我们报告说, 2-叠-1-trichloroacetimidate 捐助者可以直接从 glycals 的准备。这一过程涉及两个反应, 一锅程序从 2-叠-1-硝酸酯。21此详细的协议旨在帮助从业者成功完成高产转化。特别感兴趣的是该序列的第一步, 它着重于微波辅助加热下的热脱硝。我们也希望提供一个直观的教程, 在有机合成中使用微波反应器。

<table><tbody><tr><td>230 400 mesh silica gel</td><td>SiliCycle Inc</td><td>R10030B</td><td></td></tr><tr><td>TLC plates</td><td>SiliCycle Inc</td><td>TLG-R10014B-527</td><td></td></tr><tr><td>Ceric ammonium molybdate</td><td>Sigma-Aldrich</td><td>A1343</td><td></td></tr><tr><td>Solvent Still</td><td>Mbraun</td><td>MB-SPS-800</td><td></td></tr><tr><td>Infared spectrometer</td><td>Thermo</td><td>Thermo Electron IR100</td><td></td></tr><tr><td>Nuclear Magnetic Resonance</td><td>Bruker</td><td></td><td>400, 600 MHz</td></tr><tr><td>LC/MS</td><td>Thermo/Dionex</td><td></td><td>Single quad, ESI</td></tr><tr><td>HRMS</td><td>Agilent</td><td>Synapt G2 S HDMS</td><td></td></tr><tr><td>Microwave reactor</td><td>Anton Parr</td><td>Anton Parr G10 Monowave 200</td><td></td></tr><tr><td>DBU</td><td>Sigma-Aldrich</td><td>139009</td><td></td></tr><tr><td>CCl&lt;sub&gt;3&lt;/sub&gt;CN</td><td>Sigma-Aldrich</td><td>T53805</td><td></td></tr><tr><td>Pyridine</td><td>Sigma-Aldrich</td><td>270970</td><td></td></tr><tr><td>Acetone</td><td>Fisher Scientific</td><td>A18-20</td><td>Tech. grade</td></tr><tr><td>Phase separator</td><td>Biotage</td><td>120-1901-A</td><td></td></tr><tr><td>Rotary evaporator</td><td>Buchi</td><td>R-100</td><td></td></tr></tbody></table>

one-pot microwave-assisted conversion of anomeric nitrate-esters to trichloroacetimidates

以下过程的目标是提供一个 2-叠-1-硝酸酯的一锅转换的示范对 trichloroacetimidate 糖捐赠者。经叠硝化后的 glycal, 产品 2-叠-1-硝酸酯可以在微波辅助照射下水解。这种转变通常是通过强亲核试剂和延长反应时间来实现的。微波辐照诱导水解, 在没有试剂的情况下, 反应时间短。在脱硝后, 中间 anomeric 醇在同一锅中转化为相应的 2-叠-1-trichloroacetimidate。

本文所述的技术在三 2-叠-1-硝酸酯的水池中被证明。在每种情况下, 反应的第一步是在20分钟内完成。
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56610/56610fig2v3.jpg"> 图 2.有代表性的例子水解 (1 ->2), 和一锅转换 2-叠-1-硝酸酯的1 (1>3)。<a href="//cloudflare...

Watch this Scientific Journal Video about One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates at JoVE.com

One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

硝酸酯 Anomeric Trichloroacetimidates 的单锅微波辅助转化

一个 2-叠-1-硝酸酯可以转换为相应的 2-叠-1-trichloroacetimidate 在一个锅的程序。该手稿的目的是演示微波反应器在碳水化合物合成中的效用。

The goal of the following procedure is to provide a demonstration of the one-pot conversion of a 2-azido-1-nitrate-ester to a trichloroacetimidate ...

one-pot-microwave-assisted-conversion-anomeric-nitrate-esters-to

Research

JoVE Journal

Chemistry

7.4K 次观看.  Vanderbilt University. 一个 2-叠-1-硝酸酯可以转换为相应的 2-叠-1-trichloroacetimidate 在一个锅的程序。该手稿的目的是演示微波反应器在碳水化合物合成中的效用。

视频: One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

The direct functionalization of C-H bonds is an important and long standing goal in organic chemistry. Such transformations can be very powerful in order to streamline synthesis by saving steps, time and material compared to conventional methods that require the introduction and removal of activating or directing groups. Therefore, the functionalization of C-H bonds is also attractive for green chemistry. Under oxidative conditions, two C-H bonds or one C-H and one heteroatom-H bond can be transformed to C-C and C-heteroatom bonds, respectively. Often these oxidative coupling reactions require synthetic oxidants, expensive catalysts or high temperatures. Here, we describe a two-step procedure to functionalize indole derivatives, more specifically tetrahydrocarbazoles, by C-H amination using only elemental oxygen as oxidant. The reaction uses the principle of C-H functionalization via Intermediate PeroxideS (CHIPS). In the first step, a hydroperoxide is generated oxidatively using visible light, a photosensitizer and elemental oxygen. In the second step, the N-nucleophile, an aniline, is introduced by Br&#248;nsted-acid catalyzed activation of the hydroperoxide leaving group. The products of the first and second step often precipitate and can be conveniently filtered off. The synthesis of a biologically active compound is shown.

Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides CHIPS

A two-step procedure for the synthesis of pharmaceutically active indole-derivatives by C-H functionalization with anilines is described, using photo- and Br&#248;nsted acid catalysis.

通过中级过氧化物的抗病毒四氢咔唑衍生物的合成光化学和酸催化CH官能（筹）

The direct functionalization of C-H bonds is an important and long standing goal in organic chemistry. Such transformations can be very powerful in order ...

科研

化学

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.

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 ...

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of trifluoromethoxylated aromatic compounds remains a formidable challenge in organic synthesis. Conventional approaches often suffer from poor substrate scope, or require use of highly toxic, difficult-to-handle, and/or thermally labile reagents. Herein, we report a user-friendly protocol for the synthesis of methyl 4-acetamido-3-(trifluoromethoxy)benzoate using 1-trifluoromethyl-1,2-benziodoxol-3(1H)-one (Togni reagent II). Treating methyl 4-(N-hydroxyacetamido)benzoate (1a) with Togni reagent II in the presence of a catalytic amount of cesium carbonate (Cs2CO3) in chloroform at RT afforded methyl 4-(N-(trifluoromethoxy)acetamido)benzoate (2a). This intermediate was then converted to the final product methyl 4-acetamido-3-(trifluoromethoxy)benzoate (3a) in nitromethane at 120 &#176;C. This procedure is general and can be applied to the synthesis of a broad spectrum of ortho-trifluoromethoxylated aniline derivatives, which could serve as useful synthetic building blocks for the discovery and development of new pharmaceuticals, agrochemicals, and functional materials.

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives

An operationally simple procedure for the synthesis of ortho-trifluoromethoxylated aniline derivatives via a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxyacetamide followed by thermally induced intramolecular OCF3-migration is reported.

协议的合成<em&gt;邻</em&gt; -trifluoromethoxylated苯胺类化合物

Molecules bearing trifluoromethoxy (OCF3) group often show desired pharmacological and biological properties. However, facile synthesis of ...

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Direct cross-coupling between two alkenes via vinylic C-H bond activation represents an efficient strategy for the synthesis of butadienes with high atomic and step economy. However, this functionality-directed cross-coupling reaction has not been developed, as there are still limited directing groups in practical use. In particular, a stoichiometric amount of oxidant is usually required, producing a large amount of waste. Due to our interest in novel 1,3-butadiene synthesis, we describe the ruthenium-catalyzed olefination of electron-deficient alkenes using allyl acetate and without external oxidant. The reaction of 2-phenyl acrylamide and allyl acetate was chosen as a model reaction, and the desired diene product was obtained in 80% isolated yield with good stereoselectivity (Z,E/Z,Z = 88:12) under optimal conditions: [Ru(p-cymene) Cl2]2 (3 mol %) and AgSbF6 (20 mol %) in DCE at 110 &#186;C for 16 h. With the optimized catalytic conditions in hand, representative &#945;- and/or &#946;-substituted acrylamides were investigated, and all reacted smoothly, regardless of aliphatic or aromatic groups. Also, differently N-substituted acrylamides have proven to be good substrates. Moreover, we examined the reactivity of different allyl derivatives, suggesting that the chelation of acetate oxygen to the metal is crucial for the catalytic process. Deuterium-labeled experiments were also conducted to investigate the reaction mechanism. Only Z-selective H/D exchanges on acrylamide were observed, indicating a reversible cyclometalation event. In addition, a kinetic isotope effect (KIE) of 3.2 was observed in the intermolecular isotopic study, suggesting that the olefinic C-H metalation step is probably involved in the rate-determining step.

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

The ruthenium-catalyzed olefination of electron-deficient alkenes with allyl acetate is described here. By using aminocarbonyl as a directing group, this external oxidant-free protocol has high efficiency and good stereo- and regioselectivity, opening a novel synthetic route to (Z,E)-butadiene skeletons.

（2<em&gt;ž</em&gt;，4<em&gt;电子</em&gt;） - 通过电子缺陷烯烃与烯丙基乙酸酯的烯化反应制备二烯酰胺

Direct cross-coupling between two alkenes via vinylic C-H bond activation represents an efficient strategy for the synthesis of butadienes with high ...

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Decomposition of N-tosyl-1,2,3-triazoles with rhodium(II) acetate dimer in the presence of alcohols forms synthetically versatile N-(2-alkoxyvinyl)sulfonamides, which react under a variety of conditions to afford useful N- and O-containing compounds. Acid-catalyzed addition of alcohols or thiols to N-(2-alkoxyvinyl)sulfonamide-containing phthalans provides access to ketals and thioketals, respectively. Selective reduction of the vinyl group in N-(2-alkoxyvinyl)sulfonamide-containing phthalans via hydrogenation yields the corresponding phthalan in good yield, whereas reduction with sodium bis(2-methoxyethoxy)aluminumhydride generates a ring-opened phenethylamine analogue. Because the N-(2-alkoxyvinyl)sulfonamide functional group is synthetically versatile, but often hydrolytically unstable, this protocol emphasizes key techniques in preparing, handling, and reacting these pivotal substrates in several useful transformations.

Preparation of N-2-alkoxyvinylsulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Representative experimental procedures for the synthesis of N-(2-alkoxyvinyl)sulfonamides and subsequent conversion to phthalan and phenethylamine derivatives are presented in detail.

准备n-(2-alkoxyvinyl) 磺胺从n-tosyl-1,2,3-triazoles 和随后转换为取代 Phthalans 和 Phenethylamines

Decomposition of N-tosyl-1,2,3-triazoles with rhodium(II) acetate dimer in the presence of alcohols forms synthetically versatile ...

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 ...

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines

A synthetic process for the preparation of a variety of 1-aryl-1H-pyrazole-5-amines was developed. The microwave-mediated nature of this method makes it efficient in both time and resources and utilizes water as the solvent. 3-Aminocrotononitrile or an appropriate &#945;-cyanoketone is combined with an aryl hydrazine and dissolved in 1 M HCl. The mixture is then heated in a microwave reactor at 150 &#176;C, typically for 10-15 min. The product can be readily obtained by basifying the solution with 10% NaOH and isolating the desired compound with a simple vacuum filtration. The use of water as a solvent in this reaction lends to its ease and utility in production, and this method is easily reproducible with a variety of functional groups. Typical isolated yields range from 70-90%, and reactions can be performed on the milligram to gram scale with little to no change in observed yields. Some of the applications of these molecules and their derivatives include pesticides, anti-malarials, and chemotherapeutics, among many others.

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines

1-Aryl-1H-pyrazole-5-amines are prepared from aryl hydrazines combined with either 3-aminocrotononitrile or an &#945;-cyanoketone in a 1 M HCl solution using a microwave reactor. Most reactions are done in 10-15 minutes and pure product can be obtained via vacuum filtration with typical isolated yields of 70-90%.

微波辅助制备1-Aryl-1 H-pyrazole-5胺

A synthetic process for the preparation of a variety of 1-aryl-1H-pyrazole-5-amines was developed. The microwave-mediated nature of this method makes it ...

Preparation of 6-aminocyclohepta-2,4-dien-1-one Derivatives via Tricarbonyl(tropone)iron

aza-Michael adducts of tricarbonyl(tropone)iron are synthesized by two different methods. Primary aliphatic amines and cyclic secondary amines participate in a direct aza-Michael reaction with tricarbonyl(tropone)iron under solvent-free conditions. Less nucleophilic aniline derivatives and more hindered secondary amines add efficiently to the cationic tropone complex formed by protonation of tricarbonyl(tropone)iron. While the protocol utilizing the cationic complex is less efficient overall for accessing the aza-Michael adducts than the direct, solvent-free addition to the neutral complex, it allows the use of a broader range of amine nucleophiles. Following protection of the amine of the aza-Michael adduct as a tert-butyl carbamate, the diene is decomplexed from the iron tricarbonyl fragment upon treatment with cerium(IV) ammonium nitrate to provide derivatives of 6-aminocyclohepta-2,4-dien-1-one. These products can serve as precursors to diverse compounds containing a seven-membered carbocyclic ring. Because the demetallation requires protection of the amine as a carbamate, the aza-Michael adducts of secondary amines cannot be decomplexed using the protocol described here.

Preparation of 6-aminocyclohepta-2,4-dien-1-one Derivatives via Tricarbonyltroponeiron

Representative experimental procedures for the addition of amine nucleophiles to tricarbonyl(tropone)iron and subsequent demetallation of the resulting complexes are presented in detail.

通过三碳基(特罗酮)铁制备6-氨基环丙烯-2,4-dien-1-1衍生物

aza-Michael adducts of tricarbonyl(tropone)iron are synthesized by two different methods. Primary aliphatic amines and cyclic secondary amines participate ...

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 ...

A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis

Heteroarylation introduces heteroaryl fragments to organic molecules. Despite the numerous available reactions reported for arylation via transition metal catalysis, the literature on direct heteroarylation is scarce. The presence of heteroatoms such as nitrogen, sulfur and oxygen often make heteroarylation a challenging research field due to catalyst poisoning, product decomposition and the rest. This protocol details a highly efficient direct &#945;-C(sp3) heteroarylation of ketones under microwave irradiation. Key factors for successful heteroarylation include the use of XPhos Palladacycle Gen. 4 Catalyst, excess base to suppress side reactions and the high temperature and pressure achieved in a sealed reaction vial under microwave irradiation. The heteroarylation compounds prepared by this method were fully characterized by proton nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR) and high-resolution mass spectrometry (HRMS). This methodology has several advantages over literature precedents including broad substrate scope, rapid reaction time, greener procedure and operational simplicity by eliminating the preparation of intermediates such as silyl enol ether. Possible applications for this protocol include, but are not limited to, diversity-oriented synthesis for the discovery of biologically active small molecules, domino synthesis for the preparation of natural products and ligand development for new transition metal catalytic systems.

Heteroaryl compounds are important molecules utilized in organic synthesis, medicinal and biological chemistry. A microwave-assisted heteroarylation using palladium catalysis provides a rapid and efficient method to attach heteroaryl moieties directly to ketone substrates.

利用过渡金属催化的酮的微波辅助直接异化

Heteroarylation introduces heteroaryl fragments to organic molecules. Despite the numerous available reactions reported for arylation via transition metal ...

硝酸酯 Anomeric Trichloroacetimidates 的单锅微波辅助转化

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