Name: preparation and use of samarium diiodide (smi2) in organic synthesis: the mechanistic role of hmpa and ni(ii) salts in the samarium barbier reaction
Uploaded: 2013-02-04T09:52:00
Duration: 12 min 22 s
Description: Watch this Scientific Journal Video about Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction at JoVE.com

英国皇家空军对这项工作的支持，感谢美国国家科学基金会（CHE-0844946）。

1。合成的SMI（0.1 M） <ol><li>火焰干50毫升的圆底烧瓶中，氩气冲洗。搅拌棒和带隔垫覆盖烧瓶中。称取金属钐（0.2克，1.3毫摩尔），并加至烧瓶中，再次的烧瓶用氩气冲洗。 </li><li>加入10ml干燥的，彻底脱气的四氢呋喃（THF）其次用碘晶体（0.254克，2.0毫摩尔）。通过隔膜加入氩气的气球，这保持对反应Ar气氛的正压。 </li><li>超过3小时，在室温下剧烈搅拌该溶液。正如生成SMI 2溶液通过各种颜色的变化;橙色，然后由黄色（45分钟），以及绿色（1小时），最终变成蓝色。 </li><li>最后的海军蓝色单离子钐已经形成的迹象。为了确保悉数转换后，搅拌溶液至少3小时前使用SMI的合成。 </li></ol> 2。萨marium巴比尔反应 - 六甲基磷酰胺（HMPA）增加<ol><li>为了使SMI 2-六甲基磷酰胺复合物，取新鲜制备的SMI 2（10毫升，0.1M，1.0毫摩尔）在氩气下，通过注射器，在氩气下滴加1.75毫升六甲基磷酰胺（10当量，10毫摩尔）添加。深紫色的颜色形式。 </li><li>分别在：：附加iodododecane（0.45毫摩尔，110微升），在氩气下，3 - 戊酮（0.45毫摩尔，48微升）和2毫升的干燥THF中的清洁，干燥的小瓶。 </li><li>添加底物溶液滴加到SMI 2 /六甲基磷酰胺复合物的混合物。 </li><li>在5分钟内，搅拌，紫色的颜色将开始寻找有云，指示反应结束。 </li><li>反应完成后，暴露在空气中的解决方案，以便淬灭，在搅拌下的颜色进一步改变为黄色。 </li><li>然后将反应通过用饱和氯化铵水溶液洗涤。的溶液加入到一个分液漏斗中，并加入乙醚（5毫升）。剧烈摇动后删除顶部的有机层，增加更多的乙醚。从水层萃取两次，然后合并所有的有机层。 </li><li>洗涤有机层，用饱和硫代硫酸钠水溶液的溶液。卸下底部的水层中，随后用水，然后用最后一次洗涤后用饱和食盐水洗涤。获得最佳的有机层，并浸泡在溶液中存在的水的量的最后的任何添加硫酸镁干燥。 </li><li>通过该解决方案通过一个插头，弗罗里硅土中，以除去过量的六甲基磷酰胺。 </li><li>浓缩的溶液用旋转蒸发器以获得巴尔比耶产品。确定该产品为23 GCMS和1 H-NMR。 </li></ol> 3。巴比尔反应镍钐（ACAC）2催化剂<ol><li>称出镍（acac）的2（1摩尔％，0.01毫摩尔，0.0026克），并加入到一个干净的，干燥的小瓶含有3毫升脱气THF中，在氩气下添加的Ni（acac）的2溶液通过注射器到新鲜制备的s辨率的0.1M SMI 2（1.0毫摩尔，10毫升）。 </li><li>分别在：：附加iodododecane（0.45毫摩尔，110微升），在氩气下，3 - 戊酮（0.45毫摩尔，48微升）和2毫升的干燥THF中的清洁，干燥的小瓶。 </li><li>添加底物溶液滴加到SMI 2 /镍混合物。 </li><li>在15分钟的搅拌，蓝色将消散指示反应结束后，以形成黄绿色的颜色。 </li><li>反应完成后，暴露在空气中的解决方案，以便淬灭，在搅拌下的颜色进一步改变为黄色。工作的反应通过用0.1M水溶液洗涤。盐酸（3毫升）。的溶液加入到一个分液漏斗中，并加入乙醚（5毫升）。 </li><li>洗涤有机层，使用先前描述的协议的水溶液，硫代硫酸钠，水和盐水洗涤，硫酸镁干燥，然后干燥。浓缩溶液获得巴尔比耶产品。该产品可28 GCMS和1 H NMR确定。 </sUP&gt; </li></ol>

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没有利益冲突的声明。

这里介绍一个简单的过程使用两种最常见的添加剂产生SMI解决方案及其在有机合成中的应用。这两个例子中描绘的反应机理的认识的重要性，微调的反应SMI 2。知识库的反应机理的支柱，要按照他们的反应的要求，由合成化学家适于允许使用这种试剂。 这种单电子同质化的还原剂是很容易处理，可以从商业渠道购买。虽然上述协议是直线前进的惰性条件下，一些常见故障排除程序是：（一）确保焦磷酸钾，脱气和干，（b）如钐金属有长期暴露在空气中，它可能有一个外层氧化，用研钵和pestal清洁的金属表面暴露的金属研磨，（三）火焰干燥所有玻璃器皿和冷却的氩气下，（四）随着氮，优选氩气惰性气氛中作为购买已被证明与该金属相互作用，（e）在存在下，过量的金属的Sm-有助于保持SMI的浓度如图2所示 ，（六）resublime的碘晶体。

<table border="1"><tbody><tr><td> 的试剂的名称 </td><td> 公司 </td><td> 目录编号 </td><td> 评论（可选） </td></tr><tr><td>金属钐</td><td> ACROS </td><td> 29478-0100 </td><td> -40目，99.9％（METALS BASIS） </td></tr><tr><td> THF </td><td> OmniSolv </td><td> TX0282-1 </td><td>通过创新的技术溶剂净化系统，纯化。另外，它可以通过泵冻融法脱气</td></tr><tr><td>碘</td><td>阿法埃莎</td><td> 41955-22 </td><td> resublimed晶体，99.8％ </td></tr><tr><td> Iodododecane </td><td> ACROS </td><td> 25009-0250 </td><td> 98％ </td></tr><tr><td> 3 - 戊酮</td><td>阿法埃莎</td><td> AAA15297-AE </td><td> 99％ </td></tr><tr><td> HMPA </td><td> Alderich </td><td> H11602 </td><td> 98％;在氩气保护下蒸馏从CaO </td></tr><tr><td> NII 2 </td><td>阿法埃莎</td><td> 22893 </td><td> 99.5％（METALS BASIS） </td></tr></tbody></table>

preparation and use of samarium diiodide (smi2) in organic synthesis: the mechanistic role of hmpa and ni(ii) salts in the samarium barbier reaction

虽然最初认为是一门深奥的试剂2，SMI已经成为一种常见的有机合成化学家的工具。 SMI 2产生通过在THF分子碘的添加金属钐。1,2-3它是一种轻度的和有选择性的单电子还原剂和它的多功能性是一个发起一个宽范围的减少，包括CC键的能力的结果形成和级联或连续的反应。 SMI 2可以减少各种亚砜和砜，氧化膦，环氧化物，烷基和芳基卤化物，羰基化合物，和共轭双键的官能团，包括2-12 SMI-2介导的反应的迷人的功能之一是能够操作的结果的反应，通过选择性地使用的助溶剂或添加剂。在大多数情况下，添加剂是必要的控制的减少速度，与化疗或立体选择性反应。13-14添加剂合作mmonly微调利用SMI 2的反应性可分为三个主要的组：（1）路易斯碱磷酰三胺（HMPA，以及其他的电子给体配体，螯合剂醚，等），（2）质子源（醇类，水等），及（3）无机添加剂（镍（acac）的2，FeCl 3的 ，等）。 了解SMI 2反应的机制和该添加剂的作用，可以利用的试剂在有机合成中的全部潜力。选择的Sm-巴比艾尔反应来说明合成的重要性和机械的作用，两种常见的添加剂：HMPA和Ni（II）在该反应中。的Sm-巴比艾尔反应相似，唯一的区别是，烷基卤化物，羰基，和Sm还原剂同时混合以一锅煮的传统的格利雅反应。1,15实施例的范围内的Sm-的介导巴比艾尔反应的耦合伙伴已有报道，1,3,7,10,12，并已被UT斯达康ilized 16,17以往的研究表明，SMI 2反应的效果的添加剂HMPA增强的减排潜力，通过协调的金属钐中心的SMI 2，产生更强大的，大的自然产品的合成中的关键步骤。 13-14,18空间位阻还原剂19-21和发挥不可或缺的作用，后电子转移促进随后的粘接成形的事件的步骤22在的Sm-巴比艾尔反应在某些情况下，已被证明是HMPA另外激活烷基卤化物通过形成络合物在预平衡步骤。23 镍（II）盐的催化添加剂中频繁使用的Sm-介导的转换。24-27虽然是成功的关键，镍（II）的机械作用，在这些反应中是不知道。最近它已被证明，SMI 2降低镍（II）镍（0），并将该反应，然后进行通过organometallic镍（0）化学28 这些机理研究突出，虽然相同巴比艾尔产品被获得，使用不同的添加剂在SMI 2反应极大地改变机械的反应途径。运行这些SMI的协议引发反应。

图1示出钐巴比艾尔反应。与无添加剂的Sm-介导的反应需要72小时，得到69％的所需产物与剩余的起始原料。与另外的10个或更多当量。 HMPA的反应几乎是定量的，在几分钟之内完成。15,23随着加入1摩尔％的Ni（acac）的2，该反应是在15分钟之内完成，用97％的产率28 当HMPA被添加到SMI 2，共溶剂取代协调的THF以形成SMI 2 -磷酰三胺（HMPA）4。随着更HMPA（6-10当量）的添加，碘化物离子位移外球（ 图2）。19-21机理研究表明，当HMPA是用来在的Sm-巴比艾尔反应中的助溶剂也交互与烷基卤化物基板上形成的复合物，其中拉长的碳 - 卤键，激活的species使它更容易用Sm的减少（ 图3）。的角色HMPA，一种机制，用于与HMPA的Sm-巴尔比耶反应，提出了对通过本详细的了解（ 图4）。23烷基卤化物HMPA预平衡步骤中形成的复合物被减少的Sm / HMPA以形成自由基的速率决定步骤。自由基经历进一步减少，以形成有机钐物种夫妇与羰基和质子化后，得到最终产物。 在的情况下，镍（II）的添加剂，SMI 2最初降低镍（II）镍（0）优先超过减少基板之一。基于动力学和机理的研究，提出以下的机制（ 图5）28由SMI 2还原后，可溶性的Ni（0）烷基卤键形成一个有机镍物种物种插入。的带动下高亲氧性的性质的Sm（III）<html> ，transmetallation以形成有机钐中间的版本，镍（II）的催化循环回。的有机钐与羰基的夫妇，经质子化形成所需的叔醇。有人还观察到，通过形成镍（0）纳米粒子的Ni（II）的Sm-介导的降低，然而，这些颗粒被认为是无效和催化剂失活的源。 <img alt="图1" fo:content-width="4in" fo:src="/files/ftp_upload/4323/4323fig1highres.jpg" src="/files/ftp_upload/4323/4323fig1.jpg" /> 图1。的钐巴比艾尔反应与iodododecane和3 -戊酮。 <img alt="图2" fo:content-width="4in" fo:src="/files/ftp_upload/4323/4323fig2highres.jpg" src="/files/ftp_upload/4323/4323fig2.jpg" /> 图2。SMI 2-HMPA复杂。 ontent的“Fo：保持together.within”页面=“总是”&gt; <img alt="图3" fo:content-width="3.5in" fo:src="/files/ftp_upload/4323/4323fig3highres.jpg" src="/files/ftp_upload/4323/4323fig3.jpg" /> 图3。HMPA和烷基碘络合物。 <img alt="图4" fo:content-width="4.5in" fo:src="/files/ftp_upload/4323/4323fig4highres.jpg" src="/files/ftp_upload/4323/4323fig4.jpg" /> 图4。钐巴比尔反应机制，多余的HMPA。 <img alt="图5" fo:content-width="4in" fo:src="/files/ftp_upload/4323/4323fig5highres.jpg" src="/files/ftp_upload/4323/4323fig5.jpg" /> 图5。钐巴比尔反应体系中，氧化镍（II）建议的机制。

Watch this Scientific Journal Video about Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction at JoVE.com

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

二碘化钐（SMI编制一个简单的过程，<sub&gt; 2</sub&gt;）在THF中进行说明。的作用的两个主要的添加剂，即六甲基磷酰胺（HMPA）和Ni（乙酰丙酮）<sub&gt; 2</sub在SM介导的反应是体现在的Sm-巴比尔反应。

二碘化钐的制备和使用（SMI<sub&gt; 2</sub&gt;）在有机合成中：HMPA和镍（II）盐的钐巴尔比耶反应的机理作用

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

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Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

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