Name: retropinacol/cross-pinacol coupling reactions - a catalytic access to 1,2-unsymmetrical diols
Uploaded: 2014-04-04T13:00:00
Description: Watch this Scientific Journal Video about Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols at JoVE.com

作者感谢德意志研究联合会，德国拜耳制药公司，科聚亚公司有机金属有限公司在Bergkamen，拜耳服务公司，巴斯夫公司和沙索GmbH的财政支持。

1。钛（IV）的叔 -butoxide/Triethylchlorosilane溶液的制备<ol><li>钛（IV）， 叔丁醇钾（1毫摩尔）在10毫升无水二氯甲烷中溶解400毫克（400微升）。添加150毫克（170微升）三乙基氯硅烷（1毫摩尔）至该溶液在RT。 1ml该二氯甲烷溶液中含有0.1毫摩尔钛（IV），叔丁醇钾和0.1毫摩尔三乙基氯硅烷。 </li></ol> 2。四苯基-1,2 - 乙二醇的硼酸频哪醇 - 反应（1）与2 - 乙基丁醛</p...

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在反应时间和较高的产量总体下降是由部署的富电子的羰基化合物（17， 表1或表项19与13， 表2比较条目3）观察到。另外，在酮与大体积取代基的反应中收率的降低相当条件下观察到的（使用11， 表2比较条目12）。 尽管广泛的羰基化合物可以在本新方法被应用，不同的起始偕二醇要求的反应条件的优化。...

频哪醇偶联反应是用于对称地连二醇（1,2 - 二醇，片呐醇）制备的一般和常用的方法。综合评价在这一领域见参考文献1平尾，查特吉和Joshi 2，Ladipo 3，和Gansäuer和BLUHM 4。在对比的是，只有少数报道发表指一种高效实现跨频哪醇偶联反应，得到相应的非对称1,2 -二醇（钛（Ⅳ）氯化物/锰5，钐（Ⅱ），碘化6，镁/三甲基氯硅烷7，钒（II）8，锆/锡9，镱10）。因此，分子间的交频哪醇偶联反应，仍然是一个巨大的挑战在有机化学，这种转化，特别是催化的执行。 交叉偶联产物的形成是不受欢迎的动力学下一个经典频哪醇偶联的条件。为了获得足够数量的非对称产品的延迟增加一个羰基化合物是可能的。存在哪些正在开发这种概念的几个例子，但是它们是基于几个具体的实验操作，因此不能一概而论。另外，在这些变换1的羰基化合物的加入所需的过量导致了复杂的产物混合物11的费力的分离。就此而言，另一种是由一种反应物呈现所需的额外试剂等摩尔量的precomplexation表示。 可逆频哪醇反应的各种实例已描述12。这些导致了这样的条件可能是最好的起点的交叉偶联产物的选择性合成的代价。因为低价金属以及反应性自由基物质在原位同时形成，非对称的二元醇可在适宜的羰基反应物的存在下完全形成。给我们所知这样的方法还没有被前（Porta 等。由其他部署的AIBN的化学计量的量（2,2&#39; -偶氮二异丁腈）中所述的类似的频哪醇裂解和随后的偶联，生成报告所需基团）13。 在此协议是可视化提供了一个快速，操作上简单地访问不对称1,2 - 二醇。非对称频那醇产品大多在访问优秀的产率（&gt; 95％）。不需要的对称频那醇产品没有观察到。这个新的跨频哪醇的方法是基于一个retropinacol /跨频哪醇偶联序列。它将由benzopinacole的（1,1,2,2 -四苯基-1,2 -乙二醇，1）与2 -乙基丁醛（在醛系列）和w代表反应被证明在以下第i二乙酮（在酮系列）。

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">1.2-Dichloromethane</td>
			<td style="width:179px;">Sigma-Aldrich</td>
			<td style="width:137px;">319929</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Titanium(IV)tert-butoxide</td>
			<td>VWR International</td>
			<td>200014-852</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-Ethylbutyraldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>110094</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Benzopinacol</td>
			<td>Aldrich</td>
			<td>B9807</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triethylchlorosilane</td>
			<td>Aldrich</td>
			<td>&#160;235067</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">hexane, certified ACS</td>
			<td>Fisher scientific</td>
			<td>H29220</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">acetone, certified ACS</td>
			<td>ACROS</td>
			<td>42324</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium chloride</td>
			<td>ACROS</td>
			<td>19997</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium hydrogen carbonate</td>
			<td>ACROS</td>
			<td>12336</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Magnesium sulphate</td>
			<td>ACROS</td>
			<td>41348</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;">silica gel 60 F254 TLC plates</td>
			<td>VWR International</td>
			<td>1,057,140,001</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#160;silica gel, 0.035-0.070 for flash-chromatography</td>
			<td>ACROS</td>
			<td>240360300</td>
			<td style="width:79px;"></td>
		</tr>
	</tbody>
</table>

retropinacol/cross-pinacol coupling reactions - a catalytic access to 1,2-unsymmetrical diols

非对称的1,2 - 二醇是通过还原频哪耦合过程难以进入。成功执行这种转变势必清楚地认识和严格区分的两个类似的羰基化合物（醛→二次1,2 - 二醇或酮→三级1,2 - 二醇）。这种微调仍是一个有机的化学家一个挑战，也是一个没有解决的问题。存在着对成功执行这种转型的一些报告，但他们也不能一概而论。在这里，我们描述一个催化直接频哪耦合过程通过 retropinacol /跨频哪醇偶联序列进行。因此，不对称取代的1,2 - 二醇可以几乎定量的产率通过非常温和的条件下运作简单的性能的手段访问。人工技术，诸如注射器泵技术或反应物的延迟加法是没有必要的。我们描述的程序提供了一个非常快速的访问交频哪醇产物（1,2 - 二醇，连二醇）。进一步扩展这一新的进程， 例如，一个对映选择性的性能可为不对称的手性1,2 -二醇合成一个非常有用的工具。

在四苯基-1,2 -乙二醇和1丙酮中，有催化量的钛（Ⅳ）的醇盐，我们观察到的1,1 -二苯基-1的形成-1,2 -二醇4a和在同一时间形成的存在下反应二苯甲酮3（方案1）。没有检测到由丙酮中具有竞争力的频哪醇偶联形成相应的对称的1,2 - 二醇。然而，需要获得定量的转换非常长的和不可接受的反应时间在这些条件下。在反应发生率显着上升，观察通过添加trialkylchloros...

Watch this Scientific Journal Video about Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols at JoVE.com

Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

Retropinacol /跨频哪醇偶联反应 - 催化访问1,2  - 非对称二醇

一种新型账户的基础上retropinacol /跨频哪醇偶联机制不对称的1,2 - 二醇的合成描述。由于催化执行该反应的相当大的改进的相对于传统的交频哪醇偶合的实现。

Unsymmetrical 1,2-diols are hardly accessible by reductive pinacol coupling processes. A successful execution of such a transformation is bound to a clear ...

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