这项工作得到了中国国家自然科学基金 (21502023) 的支持。

1. 合成 1-(Iodoethynyl)-4-甲苯 (2, 1-Iodoalkynes)
<ol><li>添加133毫克 (0.36 毫摩尔) 的 TBAI 和3毫升的 CH3CN 到一个反应管, 其中含有磁性搅拌杆, 这是开放的空气。然后, 用微量泵在混合物中加入 38 μ( 0.3 毫摩尔) 的 tolylethyne。</li>
	<li>添加96.6 毫克 (0.3 毫摩尔) 的 PIDA, 以强力搅拌反应混合物10个部分在20分钟的时间内使用刮刀。</li>
	<li>在室温下搅拌反应混合物3小时。</li>
	<li>将产生的混合物倒入含有30毫升水的部位漏斗中, 用水钠2S2O3 (10%, 0.5 毫升) 淬火。用10毫升醋酸乙酯萃取水层三次。</li>
	<li>用10毫升的饱和盐水和干燥的无水硫酸钠 (0.5 克) 冲洗有机复合层。</li>
	<li>用傅书礼漏斗过滤掉硫酸硫酸钠, 在减压下浓缩滤液以获得原油。</li>
	<li>以己烷为淋洗, 用硅凝胶柱层析法提纯原油产品;纯产物, 1-(iodoethynyl)-4-甲苯, 被获得作为淡黄色液体 (71.9 毫克, 99% 屈服;Rf= 0.79)。</li>
	<li>用1H 和13C 核磁共振波谱分析产品, 高效液相色谱 (HPLC)。</li>
</ol>2. (E)-1-(12-Diiodovinyl)-4-甲苯 (3, 12-Diiodoalkenes) 的合成
<ol><li>加入124.5 毫克 (0.75 毫摩尔) 的基和1毫升的 CH3CN 到一个反应管, 其中含有磁性搅拌杆, 这是开放的空气。然后, 添加 38 ul (0.3 毫摩尔) 对tolylethyne 和3毫升的 H2O 的混合物通过微量泵。</li>
	<li>添加96.6 毫克 (0.3 毫摩尔) 的 PIDA, 以强力搅拌反应混合物10个部分在20分钟的时间内使用刮刀。</li>
	<li>在室温下搅拌反应混合物24小时。</li>
	<li>将所产生的混合物倒入含有30毫升水的部位漏斗中, 用水钠2S2O3 (10% 毫升) 淬火, 并提取含醋酸乙酯1毫升的水层三次。</li>
	<li>用10毫升盐水和干燥的无水硫酸钠 (0.5 克) 冲洗有机复合层。</li>
	<li>用傅书礼漏斗过滤掉硫酸硫酸钠, 在减压下浓缩滤液以获得原油。</li>
	<li>以己烷为淋洗, 用硅凝胶柱层析法提纯粗品。纯产物, (E)-1-(12-diiodovinyl)-4-甲苯, 被获得作为淡黄色液体 (111.9 毫克, 98% 屈服;Rf = 0.84)。</li>
	<li>用1H 和13C 核磁共振波谱分析了该产品, 并进行了 HPLC 测定。</li>
</ol>3. 合成 1-甲基-4-(12, 2-Triiodovinyl) 苯 (4, 11, 2-Triiodoalkenes)
<ol><li>添加133毫克 (0.36 毫摩尔) 的 TBAI 和1毫升的 CH3CN 到一个反应管, 其中含有搅拌杆, 这是开放的空气。然后, 添加 38 ul (0.3 毫摩尔) 的ptolylethyne 使用微量泵。</li>
	<li>添加96.6 毫克 (0.3 毫摩尔) 的 PIDA, 以强力搅拌反应混合物10个部分在20分钟的时间内使用刮刀。在室温下将反应混合物搅拌3小时。</li>
	<li>加入124.5 毫克 (0.75 毫摩尔) 的基在3毫升的 H2O 的反应混合物。</li>
	<li>添加193.2 毫克 (0.6 毫摩尔) 的 PIDA 到反应混合物10个部分在20分钟内使用刮刀。在室温下将反应混合物搅拌3小时。</li>
	<li>再添加124.5 毫克 (0.75 毫摩尔) 的基在3毫升的 H2O 和1毫升的 CH3CN 到反应混合物。</li>
	<li>在20分钟的时间内, 用刮刀将193.2 毫克 (0.6 毫摩尔) 的 PIDA 添加到反应混合物中10部分。在室温下将反应混合物搅拌12小时。</li>
	<li>将所产生的混合物倒入含有30毫升水的部位漏斗中, 用水钠2S2O3 (10% 毫升) 淬火, 并提取含醋酸乙酯2毫升的水层三次。</li>
	<li>用10毫升盐水和干燥的无水硫酸钠 (0.5 克) 冲洗有机复合层。</li>
	<li>用傅书礼漏斗过滤掉硫酸硫酸钠, 在减压下浓缩滤液以获得原油。</li>
	<li>用己烷对硅凝胶柱层析法提纯粗品, 得到纯产物, 1-甲基-4-(1, 2, 2-triiodovinyl) 苯, 作为黄液 (138.4 毫克, 93% 产量;Rf = 0.79)。</li>
	<li>用1H 和13C 核磁共振波谱分析了该产品, 并进行了 HPLC 测定。</li>
</ol>4. HPLC 法测定终端炔烃单、二、三碘的选择性
注: hplc 法测定炔烃的单、二、三碘的选择性。高效液相色谱仪采用 5 μm、4.6 毫米 x 150 毫米柱、CH3CN/H2O = 75/25 (v/v) 作为溶剂, 流速为1.0 毫升/分钟, 以及λ = 254 nm 的探测器波长。
<ol><li>高效液相色谱外标准溶液的制备<ol>
<li>精确地称出 2 (1-(iodoethynyl)-4-甲苯; 9.58 毫克, 39.58×10-3毫摩尔), 3 ((E)-1-(12-diiodovinyl)-4-甲苯; 19.29 毫克, 52.14×10-3毫摩尔) 和4 (1-甲基-4-(12, 2-triiodovinyl) 苯;11.10 毫克, 22.38×10-3毫摩尔)。</li>
		<li>在1毫升的 CH3CN 中混合并溶解这三种化合物, 并在进行 HPLC 分离之前稀释库存溶液100次。</li>
		<li>确定每种产品在 HPLC 色谱上的峰值面积比值 (%)。</li>
		<li>根据以下公式计算每种化合物的摩尔吸收率: ε2 : ε3 : ε4 = a2/n2 : 3/n3 :4/n4 其中ε是摩尔吸收, 一个峰值面积, n 摩尔重量。</li>
	</ol>
</li>
	<li>根据以下公式计算 chemoselectivity: n2 : n3 : n4 = a2/ε2 : 3/ε 3: 4/ε4
</li>
</ol>

作者没有什么特别的东西可以透露。

1-Iodoalkynes, 12-diiodoalkenes 和 11, 2-triiodoalkenes 可 chemoselectively 合成使用高价碘试剂作为有效的调解人氧化碘 (s)。这些 chemoselective 碘协议最关键的因素是碘源的性质和负载, 以及溶剂。例如, 1-iodoalkyne 2被获得作为主要产品 (52% 产量), 当 TBAI (2.5 equiv 装载) 被选择作为碘来源与甲醇结合作为溶剂 (2:3:4= 90:5: 5)。在将碘源转化为基时, 没有观察到这种选择?...

Iodoalkynes 和 iodoalkenes 广泛应用于有机合成1、2、3、4、生物活性物质的重要前体和积木, 并在合成材料和复杂分子给出了转换 C I 键5,6,7,8的容易。近年来, 炔烃的氧化碘越来越多地引起了 iodoalkyne 和 iodoalkene 衍生物的合成。迄今为止, 使用金属催化剂的有效方法9、10、11、12、高价-碘催化剂13、14、阳极氧化系统15、离子液体系统16, 基 (或 I2)-氧化剂组合17,18,19,20, 超声波21, 相转移催化剂22, n-iodosuccinimide9,22,23,24,25, N-邓布利多26,27,28,29,30,31, 格利雅试剂32, 和啉催化剂17,33,24,35已开发为碘的炔烃。最近, 我们报告了一个实用的和 chemoselective 的协议, 合成 1-iodoalkynes, 12-diiodoalkenes, 11, 2-triiodoalkenes36。该方法具有绿色实用的特点: (1) 高价碘催化剂作为氧化功能化试剂的毒性较低, 与其他传统的重金属元素氧化剂37、38、 39,40,41,42, 和 (2) TBAI 和/或基被用作碘源。此外, 在温和的条件下, 我们的系统具有良好的选择性。chemoselective 合成 1-iodoalkynes, 12-diiodoalkenes 和 11, 2 triiodoalkenes 需要精确控制各种因素, 包括组成, 氧化剂, 碘源, 和溶剂。其中, 碘源是反应 chemoselectivity 的最重要因素。在对碘源和溶剂的几种类型和荷载进行筛选后, 确定并建立了三种方法。首先, TBAI 作为碘源结合 PIDA (TBAI PIDA) 是选择性的合成 1-iodoalkynes。或者, 用 PIDA 系统有效地获得 12-diiodoalkenes。两种方法均能提供高产、高 chemoselectivity 的相应产品。相应的三 iodinationproducts, i., 11, 2-triiodoalkenes, 得到了良好的产量从一锅合成, 结合了 TBAI-PIDA 和奇 PIDA 系统36。
在这里, 我们将演示如何从 1-iodoalkynes 到 12-diiodoalkenes 和 11, 2-triiodoalkenes 在类似的反应条件下, chemoselectivity 碘的炔烃, 突出精确的控制, 可以通过明智地选择氧化剂, 碘源, 和溶剂施加。针对这种新型合成技术的发展, 对tolylethyne 作了模型基质。虽然以下协议的重点是合成 1-(iodoethynyl)-4-甲苯, (E)-1-(12-diiodovinyl)-4-甲苯和 1-甲基-4-(12, 2-triiodovinyl) 苯, 这些化合物代表 1-iodoalkynes, 12-diiodoalkenes 和 11, 2-triiodoalkenes,即, 协议是广泛的范围内, 同样的技术可以适用于 chemoselective 碘的芳香和脂肪族终端炔烃36。
使用的试剂在 chemoselective 碘的终端炔烃和小偏差的技术所描述的结果, 对目标产品的显著差异。例如, 从 TBAI 到基的碘源的变化和溶剂的变化从 ch3cn 到 ch3cn-H2O 对碘的 chemoselectivity 产生了戏剧性的影响。详细的议定书旨在帮助外地的新从业者与终端炔烃的 chemoselective 碘, 以避免在合成 1-iodoalkynes、12-diiodoalkenes 和11、2-triiodoalkenes 过程中出现许多常见的缺陷。

<table><tbody><tr><td>4-ethynyltoluene,98%</td><td>Energy Chemical</td><td>D080006</td><td></td></tr><tr><td>phenylacetylene,98%</td><td>Energy Chemical</td><td>W330041</td><td></td></tr><tr><td>1-ethynyl-4-methoxybenzene,98%</td><td>Energy Chemical</td><td>D080007</td><td></td></tr><tr><td>1-ethynyl-4-fluorobenzene,98%</td><td>Energy Chemical</td><td>D080005</td><td></td></tr><tr><td>4-(Trifluoromethyl)phenylacetylene, 98%</td><td>Energy Chemical</td><td>W320273</td><td></td></tr><tr><td>4-Ethynylbenzoic acid methyl ester,97%</td><td>Energy Chemical</td><td>A020720</td><td></td></tr><tr><td>3-Aminophenylacetylene,97%</td><td>Energy Chemical</td><td>D080001</td><td></td></tr><tr><td>3-Butyn-1-ol,98%</td><td>Energy Chemical</td><td>A040031</td><td></td></tr><tr><td>Propargylacetate,98%</td><td>Energy Chemical</td><td>L10031</td><td></td></tr><tr><td>Tetrabutylammonium Iodide,98%</td><td>Energy Chemical</td><td>E010070</td><td></td></tr><tr><td>Potassium iodide,98%</td><td>Energy Chemical</td><td>E010364</td><td></td></tr><tr><td>(diacetoxyiodo)benzene,99%</td><td>Energy Chemical</td><td>A020180</td><td></td></tr><tr><td>acetonitrile, HPLC grade</td><td>fischer</td><td>A998-4</td><td></td></tr><tr><td>magnetic stirrer</td><td>IKA</td><td></td><td></td></tr><tr><td>rotary evaporator</td><td>Buchi</td><td></td><td></td></tr><tr><td>Bruker AVANCE III 400 MHz Superconducting Fourier</td><td>Bruker</td><td></td><td></td></tr><tr><td>High-performance liquid chromatography</td><td>Shimadzu</td><td></td><td></td></tr></tbody></table>

chemoselective preparation of 1-iodoalkynes, 1,2-diiodoalkenes, and 1,1,2-triiodoalkenes based on the oxidative iodination of terminal alkynes

我们提出了 chemoselective 合成 1-(iodoethynyl)-4-甲苯, 1-(12-diiodovinyl)-4-甲苯, 1-甲基-4-(12, 2-triiodovinyl) 苯作为实际 chemoselective 制备 1-iodoalkynes 的典型例子, 12-diiodoalkenes 和 11, 2-triiodoalkenes 从 chemoselective 碘的终端炔烃介导的高价碘试剂。用p-tolylethyne 作为模型基质筛选各种碘源和/或高价碘试剂, 证实了 chemoselectivity。四丁基碘化 (TBAI) 和 (diacetoxyiodo) 苯 (PIDA) 的组合选择性地产生 1-iodoalkynes, 而基和 PIDA 的组合产生 12-diiodoalkenes。基于 TBAI-PIDA 和 PIDA 的单壶合成, 产生相应的11、2-triiodoalkenes。这些协议随后被应用于合成重要的芳香族和脂质体 1-iodoalkynes, 12-diiodoalkenes 和 11, 2-triiodoalkenes, 得到了良好的产量和优良的 chemoselectivity。

chemoselective 合成 1-iodoalkynes, 12-diiodoalkenes 和 11, 2-triiodoalkenes 的基础上的氧化碘的ptolylethyne 总结在图 1。所有的反应都暴露在空气中。本研究中的所有化合物均采用1H 和13C 核磁共振波谱、质谱和 HPLC 法, 以获得产物的结构和反应的选择性, 并探讨其纯度。所获得的产品稳定后, 在4°c 在一个冰箱四月, i. e., 高效液相色谱和1H ?...

Watch this Scientific Journal Video about Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes at JoVE.com

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

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

本文介绍了用高价碘试剂对炔烃末氧化碘的详细协议, chemoselectively 提供了 1 iodoalkynes、12 diiodoalkenes、11、2 triiodoalkenes。

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

chemoselective-preparation-1-iodoalkynes-12-diiodoalkenes-112

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Alkynes

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7.6K 次观看.  Guangdong University of Technology. 本文介绍了用高价碘试剂对炔烃末氧化碘的详细协议, chemoselectively 提供了 1 iodoalkynes、12 diiodoalkenes、11、2 triiodoalkenes。

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

Synthesis of Hypervalent Iodonium Alkynyl Triflates for the Application of Generating Cyanocarbenes

The procedures described in this article involve the synthesis and isolation of hypervalent iodonium alkynyl triflates (HIATs) and their subsequent reactions with azides to form cyanocarbene intermediates. The synthesis of hypervalent iodonium alkynyl triflates can be facile, but difficulties stem from their isolation and reactivity. In particular, the necessity to use filtration under inert atmosphere at -45 &deg;C for some HIATs requires special care and equipment. Once isolated, the compounds can be stored and used in reactions with azides to form cyanocarbene intermediates. 
The evidence for cyanocarbene generation is shown by visible extrusion of dinitrogen as well as the characterization of products that occur from O-H insertion, sulfoxide complexation, and cyclopropanation. A side reaction of the cyanocarbene formation is the generation of a vinylidene-carbene and the conditions to control this process are discussed. There is also potential to form a hypervalent iodonium alkenyl triflate and the means of isolation and control of its generation are provided. The O-H insertion reaction involves using a HIAT, sodium azide or tetrabutylammonium azide, and methanol as solvent/substrate. The sulfoxide complexation reaction uses a HIAT, sodium azide or tetrabutylammonium azide, and dimethyl sulfoxide as solvent. The cyclopropanations can be performed with or without the use of solvent. The azide source must be tetrabutylammonium azide and the substrate shown is styrene.

Herein is described the synthesis, isolation, and reactions of hypervalent iodonium alkynyl triflates (HIATs) with azides to generate cyanocarbenes. The procedures will involve air-sensitive and cryogen techniques, including cold filtration under an inert atmosphere. Handling and safety of the synthesized compounds will also be discussed.

高价碘鎓炔基三氟甲磺酸酯的生成Cyanocarbenes的合成应用

The procedures described in this article involve the synthesis and isolation of hypervalent iodonium alkynyl triflates (HIATs) and their subsequent ...

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化学

Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. Diiodomethyllithium is prepared by the deprotonation of diiodomethane with LiHMDS, in a THF/diethyl ether mixture, at -78 &#176;C in the dark. These conditions are essential for the stability of the LiCHI2 reagent generated. The subsequent dropwise addition of N-Ts aldimines to the preformed diiodomethyllithium solution affords an amino-diiodide intermediate, which is not isolated. Rapid warming of the reaction mixture to 0 &#176;C promotes cyclization to afford iodoaziridines with exclusive cis-diastereoselectivity. The addition and cyclization stages of the reaction are mediated in one reaction flask by careful temperature control.
Due to the sensitivity of the iodoaziridines to purification, assessment of suitable methods of purification is required. A protocol to assess the stability of sensitive compounds to stationary phases for column chromatography is described. This method is suitable to apply to new iodoaziridines, or other potentially sensitive novel compounds. Consequently this method may find application in range of synthetic projects. The procedure involves firstly the assessment of the reaction yield, prior to purification, by 1H NMR spectroscopy with comparison to an internal standard. Portions of impure product mixture are then exposed to slurries of various stationary phases appropriate for chromatography, in a solvent system suitable as the eluent in flash chromatography. After stirring for 30 min to mimic chromatography, followed by filtering, the samples are analyzed by 1H NMR spectroscopy. Calculated yields for each stationary phase are then compared to that initially obtained from the crude reaction mixture. The results obtained provide a quantitative assessment of the stability of the compound to the different stationary phases; hence the optimal can be selected. The choice of basic alumina, modified to activity IV, as a suitable stationary phase has allowed isolation of certain iodoaziridines in excellent yield and purity.

A protocol for the diastereoselective one-pot preparation of cis-N-Ts-iodoaziridines is described. The generation of diiodomethyllithium, addition to N-Ts aldimines and cyclization of the amino gem-diiodide intermediate to iodoaziridines is demonstrated. Also included is a protocol to rapidly and quantitatively assess the most appropriate stationary phase for purification by chromatography.

合成和Iodoaziridines纯化涉及定量选择最优固定相的色谱

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. ...

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 ...

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 ...

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. ...

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 ...

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

We introduced a regioselective and atom-economical procedure for the synthesis of 3-substituted indoles by annulation of nitrosoarenes with ethynyl ketones. The reactions were carried out achieving indoles without any catalyst and with excellent regioselectivity. No traces of 2-aroylindole products were detected. Working with 4-nitronitrosobenzene as starting material, the 3-aroyl-N-hydroxy-5-nitroindole products precipitated from the reaction mixtures and were isolated by filtration without any further purification technique. Differently from the corresponding N-hydroxy-3-aryl indoles that, spontaneously in solution, give dehydrodimerization products, the N-hydroxy-3-aroyl indoles are stable and no dimerization compounds were observed.

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

3-Aroyl-N-hydroxy-5-nitroindoles were synthesized by cycloaddition of 4-nitronitrosobenzene with a conjugated terminal alkynone in a one-step thermal procedure. Preparation of the nitrosoarene and of the alkynones were adequately reported and respectively through oxidation procedures on the corresponding aniline and on the alkynol.

A 直接、再生和原子经济合成3-Aroyl-N-羟基-5-硝基胺基，通过环加4-硝基苯与烷基诺

We introduced a regioselective and atom-economical procedure for the synthesis of 3-substituted indoles by annulation of nitrosoarenes with ethynyl ...

Preparation of Alkynes: Alkylation Reaction

<h4>Introduction</h4>
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
<img alt="Alkyne alkylation reaction using NaNH2 and ethyl bromide, chemical equation diagram." src="/files/ftp_upload/11834/11834_PT_Figure_1.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure1">
The reaction takes place in two steps:
1. The first step is the deprotonation of the terminal alkyne by the strong base forming an acetylide ion.
<img alt="Alkyne ionization reaction equation NaNH2, diagram shows acetylene converting to acetylide ion." src="/files/ftp_upload/11834/11834_PT_Figure_2.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure2">
2. The second step is a nucleophilic substitution reaction in which the acetylide ion reacts with the alkyl halide to form a new C–C bond.
<img alt="Organic reaction mechanism, Na+ and Br- ion exchange, illustrates chemical synthesis process." src="/files/ftp_upload/11834/11834_PT_Figure_3.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure3">
<h4>Reaction Mechanism —SN2 pathway </h4>
Acetylide ions are strong bases and can also function as good nucleophiles. The substitution reaction follows an SN2 pathway where the nucleophilic acetylide ion attacks the electrophilic carbon of the primary alkyl halide from the backside.
<img alt="Nucleophilic substitution reaction mechanism diagram with alkynes, NaBr formation, chemical process." src="/files/ftp_upload/11834/11834_PT_Figure_4.svg" style="text-align: center; height: 250px;" data-altupdatedat="1747908711000" data-alt="Figure4">
Since this is a concerted process, the nucleophilic attack and the departure of the leaving group takes place simultaneously to form the product with an inverted stereochemistry at the reaction center.
The reaction works best with unhindered alkyl halides like methyl halide and other primary halides. With secondary and tertiary alkyl halides, acetylide ions act as strong bases, in which case E2 elimination is the preferred pathway.
<h4>Application in organic synthesis </h4>
Alkylation of simple terminal alkynes is a useful method to extend the length of the carbon chain. Acetylene, a terminal alkyne, can be converted to a higher internal alkyne by repeated alkylation as shown below:
<img alt="Alkyne chain elongation via NaNH₂, CH₃Br; reaction equation diagram for organic synthesis." src="/files/ftp_upload/11834/11834_PT_Figure_5.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure5">

炔烃的制备:烷基化反应

Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for ...

教育

有机化学

炔烃

关键术语与概念

Preparation of Alkynes: Dehydrohalogenation

<h4>Introduction</h4>
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
<img alt="Chemical reaction diagram, alkyne synthesis, 2NaNH2/NH3, hydrogen elimination, organic chemistry." src="/files/ftp_upload/11835/11835_PT_Figure_1.svg" style="text-align: center; height: 200px;" data-altupdatedat="1747908711000" data-alt="Figure1">
<h4>Reaction Mechanism – E2 pathway</h4>
Vicinal dihalides
In the first elimination step, the strong base abstracts the proton from the dihalide that is oriented anti to the leaving group. Since E2 reactions follow a concerted pathway, the abstraction of a proton and departure of the halide leaving group occur simultaneously to form a haloalkene.
<img alt="Birch reduction mechanism diagram, showing electron flow in organic compound reaction." src="/files/ftp_upload/11835/11835_PT_Figure_2.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure2">
In the second elimination reaction, another equivalent of the strong base reacts with the haloalkene in a similar fashion to give the desired alkyne.
<img alt="Elimination reaction mechanism diagram, E2 mechanism, showing alkene formation from alkyl halide." src="/files/ftp_upload/11835/11835_PT_Figure_3.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure3">
Geminal dihalides
Likewise, geminal dihalides, when treated with two equivalents of a sodium amide, undergo double dehydrohalogenation to give alkynes.
<img alt="Alkyne formation reaction; sodium amide abstracting proton; chemical equation diagram; synthesis method." src="/files/ftp_upload/11835/11835_PT_Figure_4.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure4">
<img alt="Chemical reaction mechanism, arrow-pushing diagram, alkyne formation using sodium amide." src="/files/ftp_upload/11835/11835_PT_Figure_5.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure5">
Terminal dihalides 
Dehydrohalogenation of terminal dihalides yields terminal alkynes as the final product. In the presence of a strong base like sodium amide, terminal alkynes get converted to acetylide ions. In such cases, a third equivalent of the base is required to complete the dehydrohalogenation of the remaining haloalkene.
<img alt="Hofmann elimination reaction; chemical equations diagram; synthesis process using NaNH2; alkyne formation." src="/files/ftp_upload/11835/11835_PT_Figure_6.svg" style="text-align: center; height: 70px;" data-altupdatedat="1747908711000" data-alt="Figure6">
Protonation of the acetylide ions with water or an aqueous acid completes the reaction.
<img alt="Organic reaction mechanism with sodium acetylide, water; diagram illustrating nucleophilic attack." src="/files/ftp_upload/11835/11835_PT_Figure_7.svg" style="text-align: center; height: 50px;" data-altupdatedat="1747908711000" data-alt="Figure7">
<h4>Application in Organic Synthesis</h4>
Dehydrohalogenation of vicinal dihalides is a useful intermediate step in the conversion of alkenes to alkynes. For example, chlorination of 1-propene gives 1,2-dichloropropane – a vicinal dihalide, which upon double dehydrohalogenation yields 1-propyne.
<img alt="Alkene to alkyne conversion diagram; chemical reaction mechanism, dichlorination, dehydrohalogenation." src="/files/ftp_upload/11835/11835_PT_Figure_8.svg" style="text-align: center; height: 60px;" data-altupdatedat="1747908711000" data-alt="Figure8">
Similarly, alkynes can also be synthesized from ketones via dehydrohalogenation of geminal dihalides. For example, treatment of acetone with phosphorous pentachloride yields 2,2-dichloropropane – a geminal dihalide, which undergoes double dehydrohalogenation to give 1-propyne.
<img alt="Organic synthesis mechanism; ketone to alkyne via substitution and elimination; chemical reaction diagram." src="/files/ftp_upload/11835/11835_PT_Figure_9.svg" style="text-align: center; height: 80px;" data-altupdatedat="1747908711000" data-alt="Figure9">

炔烃的制备:脱卤化氢

Introduction
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ...

Preparation of Aldehydes and Ketones from Alcohols, Alkenes, and Alkynes

Aldehydes and ketones are prepared from alcohols, alkenes, and alkynes via different reaction pathways. Alcohols are the most commonly used substrates for synthesizing aldehydes and ketones. The conversion of alcohol to aldehyde, which involves the oxidation process, depends on the class of the alcohol used and the strength of the oxidizing agent. For instance, primary alcohol will form an aldehyde when treated with a weak oxidizing agent; however, it gets over-oxidized to a carboxylic acid in the presence of a strong oxidizing agent. Hence, a mild oxidant like pyridinium chlorochromate is used to convert primary alcohols to aldehydes.
Similarly, Swern and Dess&#8211;Martin oxidations, which employ weaker oxidizing agents, convert primary alcohols to aldehydes. The strength of the oxidizing agent is irrelevant when converting secondary alcohol to a ketone. Both mild and strong oxidants give ketones from secondary alcohols.
Unsaturated hydrocarbons like alkenes undergo an ozonolysis reaction to give aldehydes and ketones. The product formed depends on the substitution present across the double bond in an alkene. A monosubstituted alkene forms formaldehyde and another aldehyde molecule. However, disubstitution gives rise to two cases. A 1,1-disubstituted alkene upon ozonolysis forms a mixture of formaldehyde and ketone, while a 1,2-disubstituted alkene yields a mixture of aldehydes. Both aldehydes and ketones are formed when trisubstituted alkenes undergo ozonolysis, while tetrasubstituted alkenes form ketones exclusively.
Alkynes&#160;also form aldehydes and ketones under hydroboration-oxidation and acid-catalyzed hydration reaction conditions. The hydroboration-oxidation reaction favors anti-Markovnikov&#8217;s addition. Hence terminal alkynes form aldehydes, and internal alkynes&#160;yield ketones. On the other hand, the acid-catalyzed hydration reaction follows Markonikov&#8217;s addition, and thus both terminal and internal alkynes generate&#160;ketones.

从醇、烯烃和炔烃制备醛和酮

Aldehydes and ketones are prepared from alcohols, alkenes, and alkynes via different reaction pathways. Alcohols are the most commonly used substrates for ...