We are grateful to the Research Corporation for Science Advancement (20092), the National Science Foundation (CHE-1362140), and Texas State University for their generous support.

1，合成Diamidocarbene（化合物1） <ol><li>烘箱干燥的100ml Schlenk烧瓶中，连接到一个高性能的真空歧管，抽真空，并用氮气冲洗。添加搅拌棒的烧瓶中，并盖用橡胶隔膜。称出N，N&#39;-dimesitylformamidine 12（1.5克，5.35毫摩尔），并将其添加到该烧瓶中，同时用氮气冲洗。 <ol><li>加入（通过干的脱氧的注射器）30ml无水，脱气的二氯甲烷（DCM），随后加入三乙胺（1.1毫升，8.0毫摩尔，1.5当量）。冷却，在冰浴将得到的溶液至0℃。 </li><li> （通过一个干的脱氧的注射器）dimethylmalonyl氯化物逐滴加入（0.75毫升，5.60毫摩尔，1.05当量）冷却的溶液中。在此外，让溶液在氮气气氛下搅拌，在0℃下搅拌1小时。一旦溶液搅拌1小时，除去真空下所有的挥发性物质。 </li><li>添加干燥脱气己烷的混合溶剂：DCM（2:1（体积），24毫升总体积），以在反应烧瓶中的残余物。让该混合物磨碎10分钟。 </li><li>同时，附装有介质的孔隙率的玻璃料，以烘箱干燥的100ml Schlenk烧瓶的顶部有一个过滤管（参见图1）。要过滤管，补充足够的烘干硅藻土来创建一个过滤器插件约2英寸高。密封该过滤筒用橡胶隔膜，并通过附加的Schlenk烧瓶中，真空腔抽真空，在系统上。 <img alt="图1" fo:content-width="2.5in" src="/files/ftp_upload/52149/52149fig1highres.jpg" width="250" /> 图1过滤装置组件，用于从碳烯的前体1-HCl和2 -盐酸除去的[HNEt 3] [氯]，该装置也可以用来除去NaCl卡宾1和2的合成过程中形成的。 </li><li>过滤装置组件，用于从碳烯的前体1-HCl和2 -盐酸除去的[HNEt 3] [氯]。该设备也是我们编辑删除卡宾1和2的合成过程中盐形成。 </li><li>一旦过滤装置已经组装并在真空条件下，通过套管转移的白色悬浮液在反应烧瓶中放入滤管。一定要定期地拉真空上收集的Schlenk烧瓶以确保所有的溶液过滤通过硅藻土。 </li><li>通过橡胶隔膜用注射器（1，体积加入18ml总体积2）：通过将干的，脱气的己烷的混合溶剂洗涤硅藻土DCM中。再次，定期地拉在收集的Schlenk烧瓶中的真空，以确保所有的溶液过滤通过硅藻土。 </li><li>断开过滤管的集合Schlenk烧瓶中在氮气的冲洗，然后密封收集Schlenk烧瓶用玻璃塞。除去所有在真空下从采集的Schlenk烧瓶中的溶剂，得到的前体diamidocarbene 1（1-HCl）的作为空气/湿气敏感的白色粉末在大约92％收益率（2.04克）。该产品可以通过1 H和13 C NMR谱（CDCL 3）13,14进行验证。转移化合物1盐酸成之前的下一个步骤存储的手套箱中。 </li></ol></li><li>为了准备diamidocarbene 1，首先转移烘箱干燥的100ml Schlenk烧瓶中搅拌棒和玻璃塞成一个充满氮气的手套箱。 <ol><li>称取卡宾前体1 - 盐酸（0.600克，1.45 mmol）和六甲基二硅钠（加入NaHMDS，0.267克，1.46毫摩尔），并将这两个固体放入Schlenk烧瓶。 </li></ol></li><li>添加干燥，脱气的苯（25毫升）中的两种固体中的Schlenk烧瓶中，然后塞住烧瓶。在这一点上，该Schlenk烧瓶从手套箱中取出。 </li><li>搅拌该卡宾在RT的溶液30分钟。在整个反应过程中，溶液会变成混浊的橙黄色。在这段时间内，建立类似于上面所描述的（使用1 I的过滤装置硅藻土NCH插头）为1的HCl的合成。 </li><li>过滤卡宾溶液（以除去沉淀的NaCl）中所描述的前体1-HCl中。一旦溶液被过滤，除去所有使用真空，得到粗卡宾1，其为黄色 - 橙色粉末的挥发物。通过洗涤该固体用冷的己烷（约10毫升），得到分析纯的化合物作为空气/湿气敏感的白色粉末在大约85％的产率（0.462克）进一步纯化卡宾1。 1 H和13 C-NMR光谱（C 6 D 6）13验证产品。 </li></ol> 2，合成Monoamidocarbene（化合物2） <ol><li>烘箱干燥250毫升Schlenk烧瓶连接到一个高性能的真空歧管，抽真空，并用氮气冲洗。添加搅拌棒的烧瓶中，并盖用橡胶隔膜。称出N，N&#39;-dimesitylformamidine（3.00克，10.70毫摩尔），并将其添加到该烧瓶中，同时用氮气冲洗。 <ol><li>添加（六干的脱氧的注射器）125毫升干燥，脱气的DCM随后加入三乙胺（2.25毫升，16.05毫摩尔，1.5当量）。冷却，在冰浴将得到的溶液至0℃。 </li><li> （通过一个干的脱氧的注射器），3 - 氯代磺酰氯逐滴加入（1.54毫升，11.77毫摩尔，1.1当量）到冷却的溶液中。在此外，让溶液在氮气气氛下搅拌，在0℃下进行30分钟。然后逐渐温热溶液至室温，然后在真空下除去所有挥发性物质。除去溶剂后，将白色固体残留物会留。 </li><li>加入甲苯（200ml）中的白色固体，并允许该悬浮液，以磨碎1小时。然后经硅藻土过滤的使用中孔玻璃上的1英寸插头混合物布氏漏斗。 </li><li>甲苯溶液转移至500ml圆底烧瓶中搅拌棒。连接回流冷凝器的烧瓶中，并加热该溶液至回流（110℃）16小时。在çourse反应，生成白色沉淀就会形成。 </li><li> 16小时后，使悬浮液冷却至室温。在这段时间内，更坚实将沉淀从溶液中。收集经真空过滤固体并洗涤固体用冷甲苯（3×20毫升）。 </li><li>干燥得到的白色，使用真空固体，得到约91％的产率（3.32 G）的前体monoamidocarbene 2（2-HCl）的作为空气稳定的白色粉末。该产品可以通过1 H和13 C NMR谱（CDCL 3）15进行验证。转移化合物2的HCl转化为之前的下一个步骤存储的手套箱中。 </li></ol></li><li>要准备monoamidocarbene 2，第一转移烘箱干燥的100ml Schlenk烧瓶中搅拌棒和玻璃塞成一个充满氮气的手套箱。 <ol><li>称取卡宾前体2 - 盐酸（0.500克，1.25毫摩尔），并加入NaHMDS（0.241克，1.32毫摩尔），并将这两种固体放入Schlenk烧瓶。 </li><li>添加干燥，脱气苯（45毫升）中的两种固体中的Schlenk烧瓶中，然后塞住烧瓶。在这一点上，该Schlenk烧瓶从手套箱中取出。 </li><li>搅拌该卡宾在RT的溶液30分钟。在反应过程中，溶液会变成混浊的黄色。同时，设置了类似于上述的1-HCl中使用硅藻土1英寸插头合成一个的过滤装置。 </li><li>过滤卡宾溶液（以除去沉淀的NaCl）中所描述的卡宾1一旦溶液被过滤，除去所有使用真空，得到粗卡宾2为褐色粉末的挥发物。通过反复洗涤该固体，用戊烷，得到分析纯的化合物作为空气/湿气敏感的白色粉末在大约62％的产率（0.309克）进一步纯化卡宾2。 1 H和13 C-NMR光谱（C 6 D 6）15验证产品。 </li></ol></li></ol> 3，合成三（phosphaalkenyl）膦（化合物3） 警告声明：白磷是极其引火以及有毒的，应在手套箱谨慎处理只要有可能。 <ol><li>为了使三（phosphaalkenyl）膦（化合物3），称出diamidocarbene 1（0.100克，0.266毫摩尔，3当量）和白色磷（P 4 0.011克，0.089毫摩尔，1当量）在含氮内与灯填充的手套箱关闭。在这前几步为P 4对光敏感关闭尽可能多的灯在实验室。 </li><li>两个固体添加到被包裹在铝箔20毫升玻璃小瓶中。添加干燥，脱气的二乙醚（Et 2 O等，10ml）加 ​​到该固体，然后盖上小瓶。搅拌在黑暗中的淤浆搅拌2小时。在反应过程中，一个明亮的橙红色沉淀就​​会形成。 </li><li>通过使用10ml的中孔玻璃过滤分离出红色固体布氏漏斗。日洗e红色固体用Et 2 O（4×5ml）中，然后干燥在真空下，得到化合物3为分析纯的空气稳定的化合物在约82％的产率，0.092克（基于P 4）。 1 H和31 P NMR光谱（C 6 D 6）11验证产品。 </li></ol> 4，合成卡宾稳定P 8同素异形体（化合物4） <ol><li>方法A <ol><li>使卡宾稳定P 8同素异形体（化合物4），称出monoamidocarbene 2（0.100g克，0.276毫摩尔，3当量）和P 4（11.4毫克，0.092毫摩尔，1当量）在氮气填充的手套箱内与灯盒被关闭。在这前几步为P 4对光敏感关闭尽可能多的灯在实验室。 </li><li>两个固体添加到被包裹在铝箔20毫升玻璃小瓶中。添加干燥，脱气的二乙醚（Et 2 O等，10ml）加 ​​到该固体，然后盖上小瓶。当此外，乙醚，流年暗绿色的颜色变化迅速，以明亮的橙色。搅拌在黑暗中的淤浆搅拌2小时。在反应过程中，一个明亮的橙色沉淀就会形成。 </li><li>通过使用10ml的中孔玻璃过滤分离出橙色固体布氏漏斗。用Et 2 O（4×2毫升）洗涤橙色固体，然后干燥在真空下，得到化合物4作为与分析纯的空气稳定的化合物在约51％的产率，39.5毫克（基于P 4）。通过1 H和31 P NMR光谱（THF-D8）11确认该产品。 </li></ol></li><li>方法B <ol><li>称出monoamidocarbene 2（0.100g克，0.276毫摩尔，2当量）和P 4（17.1毫克，0.138毫摩尔，1当量）与灯充满氮气的手套箱内截止。在这前几步为P 4对光敏感关闭尽可能多的灯在实验室。 </li><li>经由两种固体加入到20ml的玻璃升被包裹在铝箔。添加干燥，脱气的己烷（10ml）加到该固体，然后盖上小瓶。在加入乙醚，流年暗绿色的颜色变化迅速，以明亮的橙色。搅拌在黑暗中的淤浆搅拌2小时。在反应过程中，一个明亮的橙色沉淀就会形成。 </li><li>使用10毫升培养基的孔隙率多孔玻璃布氏漏斗通过过滤分离出橙色固体，然后干燥在真空下，得到化合物4作为与分析纯的空气稳定的化合物在约75％的产率，87.7毫克（基于P 4）。通过1 H和31 P NMR光谱（THF-D8）验证产品11 </li></ol></li></ol>合成化合物5：5，通过[4 +2]环加成捕获瞬态Ë-1,2 -二（phosphaalkenyl）diphosphene <ol><li>以制备化合物5中，称出monoamidocarbene 2（0.300mL克，0.828毫摩尔，2当量）和P 4（51.3毫克，0.414毫摩尔，1当量） 九月另行购买的灯充满氮气的手套箱内截止。在这前几步为P 4对光敏感关闭尽可能多的灯在实验室。 </li><li>在P 4添加到20ml的玻璃瓶中，然后添加干燥，脱气的己烷溶液（18毫升）的小瓶中。接着，在己烷中添加2,3 -二甲基-1,3 -丁二烯（2毫升）到P 4的悬浮液。 </li><li>而己烷/ P 4的悬浮液快速搅拌下，在一个部分中添加卡宾2，为固体。受瞬间变成亮黄色。过了一段约10分钟，所有的固体会溶解之后的亮黄色固体沉淀。在这一点上，让该悬浮液搅拌4小时。 </li><li> 4小时后，用10毫升培养基的孔隙率多孔玻璃布氏漏斗通过过滤分离出黄色固体。此黄色固体为化合物5（纯度&gt; 90％由两个1 H和31 P NMR）。集中黄色清液至干并结合黄色残余物用过滤的黄色固体。 </li><li>为了净化化合物5，重结晶合并黄色固体从1:3（体积比）的DCM：己烷液（1​​2mL总体积），在-30℃的手套箱O 2 / N C冰箱。这个过程将得到5为分析纯的空气稳定的黄色晶体在约71％的产率，0.301克（基于P 4）。 1 H和31 P NMR光谱（C 6 D 6）11验证产品。 </li></ol>

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The authors have nothing to disclose.

一个直接的方法生成羰基饰卡宾及其应用白磷激活在这里提出。用于合成卡宾在协议中关键的步骤是：（一）确保所有溶剂在使用前进行适当干燥，（二）确保除酰氯的甲脒是做得很慢，（c）如果是硅藻土不烘箱干燥最少12小时的在180℃下，在1 -HCl的水解以及卡宾1和2发生。在一些情况下，白磷将转换为红磷。对于P 4的活化反应中，至关重要的是，该...

稳定的卡宾已成为无处不在的试剂均相催化1，2有机催化，材料科学3,4，最近主族化学5-9。在后者的情况下，稳定的卡宾最近已被用在白色的磷（P 4）5-9的活化和官能化。直接转换P 4成的有机磷化合物的能力已成为一个热门的研究目标，努力开发出规避使用氯化或oxychlorinated磷前体“更绿色”的方法。尽管它们的广泛使用，配制和操作卡宾和活性化合物，如对4的可能是一个艰巨的任务。为此，我们编写了这份手稿，以提供清晰，简明的协议，将允许所有技能水平的合成化学家合成和操作两个非常独特的稳定çarbenes。此外，P 4的使用所描述的卡宾活化是详细的。 在此我们详细的协议为两缺电子的羰基饰卡宾的合成。我们选择这些卡宾，因为他们在电性能的唯一区别，而不是他们的立体参数，使它们非常适合学习的反应卡宾电子产品的影响。卡宾电子方面的反应性的重要性是由已报道由伯特兰和Robinson 5,8通式卡宾-P 2 -carbene的两个类似的化合物举例说明。贝特朗的P 2衍生物是由两个环状烷基氨基卡宾（民航）配位体的支持，并且在结构上，photophysically，并且比鲁宾逊的化合物，它是由两个N-杂环卡宾（的NHCs）5,8支承的P 2片段电化学不同。事实上，贝特朗的P 2 </子&gt;络合物的特征在于，其为黄色固体，具有碳烯 - 对 - 磷双键在固体状态，而报道罗宾逊的衍生物是一种暗红色固体，它包含NHC→第配价键。这种结构上的差异也表现电化学使得鲁宾逊的化合物中含有较多的富电子的磷中心，可以进行相反贝特朗的化合物可逆1或2电子氧化作用，它只能进行单一的可逆氧化10。 基于上述研究，我们的极大兴趣，学习P 4使用高电diamido-和monoamidoamino卡宾，以确定是否磷小说卡宾稳定的同素异形体，可以准备激活。我们专注于diamidocarbene（DAC）1，和monoamidoamino卡宾（MAAC）2只在各自electrophilicities有差异，以interrog吃了P 4活化什么样的角色卡宾电子游戏。有趣的是，当多电DAC的情况下，三（phosphaalkenyl）膦（3）可以被分离为专属产物，而当MAAC时，卡宾稳定P 8同素异形体（4），可以得到11。我们还询问机制形成（4），并发现它是通过[2 +2] cylcoaddition二聚化的过渡diphosphene的反应而形成的。本diphosphene的存在通过用2,3 -二甲基-1,3 -丁二烯诱捕它提供的[4 +2]环加成加合物5证实。该协议用 ​​于合成这些羰装饰卡宾和其相应的P 4活化的化合物本文描述了。

<table border="0" cellpadding="0" cellspacing="0" width="580">
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:171px;">2,4,6-trimethylaniline</td>
			<td style="width:92px;">Alfa Aesar</td>
			<td style="width:123px;">AAA13049-0E</td>
			<td style="width:195px;">98%</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:171px;">Triethylorthoformate</td>
			<td style="width:92px;">Alfa Aesar</td>
			<td style="width:123px;">AAA13587</td>
			<td style="width:195px;">98%</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:171px;">Dimethylmalonyl dichloride</td>
			<td style="width:92px;">TCI</td>
			<td style="width:123px;">D2723</td>
			<td style="width:195px;">&#62;98%</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:171px;">3-chloro-pivaloyl chloride</td>
			<td style="width:92px;">Aldrich</td>
			<td style="width:123px;">225703-25G</td>
			<td style="width:195px;">98%</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:171px;">Triethylamine</td>
			<td style="width:92px;">Alfa Aesar</td>
			<td style="width:123px;">AAA12646</td>
			<td style="width:195px;">Stored over dried, activated 3 &#197; molecular sieves</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:171px;">Celite&#8482; 545</td>
			<td style="width:92px;">EMD</td>
			<td style="width:123px;">CX0574-3D</td>
			<td style="width:195px;">Oven-dried at 180 &#176;C for a minimum of 12 hrs</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:171px;">Sodium hexamethyldisilazide</td>
			<td style="width:92px;">Across</td>
			<td style="width:123px;">200014-462</td>
			<td style="width:195px;">95+%</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:171px;">2,3-dimethyl-1,3-butadiene</td>
			<td style="width:92px;">Alfa Aesar</td>
			<td style="width:123px;">AAAL04207-09</td>
			<td style="width:195px;">98%</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:171px;">dichloromethane</td>
			<td style="width:92px;">EMD</td>
			<td style="width:123px;">DX0835-5</td>
			<td style="width:195px;">Purified through solvent purification system, or standard methods</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:171px;">tetrahydrofuran</td>
			<td style="width:92px;">Mallinckrodt</td>
			<td style="width:123px;">8498-09</td>
			<td style="width:195px;">Purified through solvent purification system, or standard methods</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:171px;">Hexanes</td>
			<td style="width:92px;">EMD</td>
			<td style="width:123px;">HX0299-3</td>
			<td style="width:195px;">Purified through solvent purification system, or standard methods</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:171px;">Benzene</td>
			<td style="width:92px;">EMD</td>
			<td style="width:123px;">BX0220-5</td>
			<td style="width:195px;">Purified through solvent purification system, or standard methods</td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:171px;">Toluene</td>
			<td style="width:92px;">BDH</td>
			<td style="width:123px;">1151-19L</td>
			<td style="width:195px;">Purified through solvent purification system, or standard methods</td>
		</tr>
		<tr height="127">
			<td height="127" style="height:127px;width:171px;">white phosphorus</td>
			<td style="width:92px;">Generously donated from the Texas A&#38;M chemistry store room.</td>
			<td style="width:123px;">NA</td>
			<td style="width:195px;">Purified through sublimation and transferred directly into a glovebox while under vacuum in the sublimator</td>
		</tr>
	</tbody>
</table>

preparation and use of carbonyl-decorated carbenes in the activation of white phosphorus

在这里，我们提出了一个协议，两个不同的羰基饰卡宾的合成。两个卡宾可以使用多克规模的量几乎相同的方法来制备。这个手稿的目标是明确的细节如何处理，并准备这些独特的卡宾，使得任何技术水平的合成化学家能够与他们合作。描述这两个卡宾是一个diamidocarbene（DAC，卡宾1）和monoamidoaminocarbene（MAAC 2）。这些卡宾是高度缺电子，因此显示反应曲线是非典型的较传统的N-杂环卡宾。此外，这两个卡宾的区别仅在于它们的电性质，而不是其空间的参数，使它们非常适合用于研究电子的影响力如何卡宾反应。为了证明这个现象，我们也描述了使用这些卡宾白色磷（P 4）激活。根据carbenë使用两个非常不同的含磷化合物可被分离。当DAC 1的情况下，三（phosphaalkenyl）膦可被分离为专属产物。显着然而，当MAAC 2加入到P 4在相同的反应条件下，磷的一个意想不到的卡宾负载P 8同素异形体是完全隔离的。机制研究表明，通过瞬时diphosphene已捕获通过用2,3 -二甲基-1,3 -丁二烯的[2 +2]环加成二聚化此碳烯-支持P 8同素异形体的形式。

以分离三（phosphaalkenyl）膦，如3或从白磷在P 8 -allotrope（4）的能力依赖于使用的电卡宾的激活P 4四面体11,16。因此，重要的是，制备卡宾具有增强的π-酸，并通过扩展电性， 图2示出了卡宾前体1的HCl和其后续的脱质子化的合成，得到diamidocarbene 1 13。 diamidocarbene 1的合成中，可以实现在单一...

Watch this Scientific Journal Video about Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus at JoVE.com

Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus

Here, we present a protocol for the synthesis of two carbonyl-decorated carbenes. The protocol makes these interesting compounds readily available to chemists of all skill levels. In addition to the synthesis of these two carbenes, their use in the activation of white phosphorus is also described.

羰基饰卡宾的白色磷的活化制备方法和用途

Here we present a protocol for the synthesis of two distinct carbonyl-decorated carbenes. Both carbenes can be prepared using nearly identical procedures ...

preparation-use-carbonyl-decorated-carbenes-activation-white

Research

JoVE Journal

Chemistry

13.5K 次观看.  Texas State University. Here, we present a protocol for the synthesis of two carbonyl-decorated carbenes. The protocol makes these interesting compounds readily available to chemists of all skill levels. In addition to the synthesis of these two carbenes, their use in the activation of white phosphorus is also described.

视频: Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus

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

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3
Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23
Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28
These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described.

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

A straightforward procedure for the preparation of samarium diiodide (SmI2) in THF is described. The role of two main additives namely hexamethylphosphoramide (HMPA) and Ni(acac)2 in Sm mediated reactions is demonstrated in the Sm-Barbier reaction.

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 ...

科研

化学

The Use of Gas Chromatography to Analyze Compositional Changes of Fatty Acids in Rat Liver Tissue during Pregnancy

Gas chromatography (GC) is a highly sensitive method used to identify and quantify the fatty acid content of lipids from tissues, cells, and plasma/serum, yielding results with high accuracy and high reproducibility. In metabolic and nutrition studies GC allows assessment of changes in fatty acid concentrations following interventions or during changes in physiological state such as pregnancy. Solid phase extraction (SPE) using aminopropyl silica cartridges allows separation of the major lipid classes including triacylglycerols, different phospholipids, and cholesteryl esters (CE). GC combined with SPE was used to analyze the changes in fatty acid composition of the CE fraction in the livers of virgin and pregnant rats that had been fed various high and low fat diets. There are significant diet/pregnancy interaction effects upon the omega-3 and omega-6 fatty acid content of liver CE, indicating that pregnant females have a different response to dietary manipulation than is seen among virgin females.

Pregnancy leads to significant changes to the fatty acid composition of maternal tissues. Lipid profiles can be obtained via gas chromatography to allow identification and quantification of fatty acids in individual lipid classes among rats fed various high and low fat diets during pregnancy.

使用气相色谱怀孕期间分析脂肪酸组成的变化在大鼠肝组织

Gas chromatography (GC) is a highly sensitive method used to identify and quantify the fatty acid content of lipids from tissues, cells, and plasma/serum, ...

Use of Stopped-Flow Fluorescence and Labeled Nucleotides to Analyze the ATP Turnover Cycle of Kinesins

The kinesin superfamily of microtubule associated motor proteins share a characteristic motor domain which both hydrolyses ATP and binds microtubules. Kinesins display differences across the superfamily both in ATP turnover and in microtubule interaction. These differences tailor specific kinesins to various functions such as cargo transport, microtubule sliding, microtubule depolymerization and microtubule stabilization. To understand the mechanism of action of a kinesin it is important to understand how the chemical cycle of ATP turnover is coupled to the mechanical cycle of microtubule interaction. To dissect the ATP turnover cycle, one approach is to utilize fluorescently labeled nucleotides to visualize individual steps in the cycle. Determining the kinetics of each nucleotide transition in the ATP turnover cycle allows the rate-limiting step or steps for the complete cycle to be identified. For a kinesin, it is important to know the rate-limiting step, in the absence of microtubules, as this step is generally accelerated several thousand fold when the kinesin interacts with microtubules. The cycle in the absence of microtubules is then compared to that in the presence of microtubules to fully understand a kinesin&#8217;s ATP turnover cycle. The kinetics of individual nucleotide transitions are generally too fast to observe by manually mixing reactants, particularly in the presence of microtubules. A rapid mixing device, such as a stopped-flow fluorimeter, which allows kinetics to be observed on timescales of as little as a few milliseconds, can be used to monitor such transitions. Here, we describe protocols in which rapid mixing of reagents by stopped-flow is used in conjunction with fluorescently labeled nucleotides to dissect the ATP turnover cycle of a kinesin.

Kinesins are characterized by nucleotide-dependent interaction with microtubules: a cycle of ATP turnover coupled to a cycle of microtubule interaction. Here, we describe protocols to analyze the kinetics of individual nucleotide transitions in the ATP turnover cycle of a kinesin using fluorescently labeled nucleotides and stopped-flow fluorescence.

利用停流荧光和标记的核苷酸来分析驱动蛋白的ATP周转周期

The kinesin superfamily of microtubule associated motor proteins share a characteristic motor domain which both hydrolyses ATP and binds microtubules. ...

HPLC Measurement of the DNA Oxidation Biomarker, 8-oxo-7,8-dihydro-2&#8217;-deoxyguanosine, in Cultured Cells and Animal Tissues

Oxidative stress is associated with many physiological and pathological processes, as well as xenobiotic metabolism, leading to the oxidation of biomacromolecules, including DNA. Therefore, efficient detection of DNA oxidation is important for a variety of research disciplines, including medicine and toxicology. A common biomarker of oxidatively damaged DNA is 8-oxo-7,8-dihydro-2&#39;-deoxyguanosine (8-oxo-dGuo; often erroneously referred to as 8-hydroxy-2&#39;-deoxyguanosine (8-OH-dGuo or 8-oxo-dG)). Several protocols for 8-oxo-dGuo measurement by high pressure liquid chromatography with electrochemical detection (HPLC-ED) have been described. However, these were mainly applied to purified DNA treated with pro-oxidants. In addition, due to methodological differences between laboratories, mainly due to differences in analytical equipment, the adoption of published methods for detection of 8-oxo-dGuo by HPLC-ED requires careful optimization by each laboratory. A comprehensive protocol, describing such an optimization process, is lacking. Here, a detailed protocol is described for the detection of 8-oxo-dGuo by HPLC-ED, in DNA from cultured cells or animal tissues. It illustrates how DNA sample preparation can be easily and rapidly optimized to minimize undesirable DNA oxidation that can occur during sample preparation. This protocol shows how to detect 8-oxo-dGuo in cultured human alveolar adenocarcinoma cells (i.e., A549 cells) treated with the oxidizing agent KBrO3, and from the spleen of mice exposed to the polycyclic aromatic hydrocarbon dibenzo(def,p)chrysene (DBC, formerly known as dibenzo(a,l)pyrene, DalP). Overall, this work illustrates how an HPLC-ED methodology can be readily optimized for the detection of 8-oxo-dGuo in biological samples.

HPLC Measurement of the DNA Oxidation Biomarker, 8-oxo-7,8-dihydro-2&amp;#8217;-deoxyguanosine, in Cultured Cells and Animal Tissues

The goal of this protocol is the detection of the DNA oxidation marker, 8-oxo-7,8-dihydro-2&#39;-deoxyguanosine (8-oxo-dGuo) by HPLC-ED, in DNA from cultured cells or animal tissues.

该DNA氧化标志物的高效液相色谱法测量，8-氧代-7,8-二氢-2&#39;-脱氧鸟苷，在培养细胞和动物组织

Oxidative stress is associated with many physiological and pathological processes, as well as xenobiotic metabolism, leading to the oxidation of ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

蛋白质生物缀合物的合成<em&gt;通过</em&gt;半胱氨酸马来酰亚胺化学

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Visualization of Ambient Mass Spectrometry with the Use of Schlieren Photography

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass spectrometer, it is necessary to characterize and understand the physical principles of the source. Most commercial ambient ionization sources utilize jets of nitrogen, helium, or atmospheric air to facilitate the ionization of the analyte. As a consequence, schlieren photography can be used to visualize the gas streams by exploiting the differences in refractive index between the streams and ambient air for visualization in real time. The basic setup requires a camera, mirror, flashlight, and razor blade. When properly configured, a real time image of the source is observed by watching its reflection. This allows for insight into the mechanism of action in the source, and pathways to its optimization can be elucidated. Light is shed on an otherwise invisible situation.

This paper presents a protocol for the visualization of gaseous streams of an ambient ionization source using schlieren photography and mass spectrometry.

环境质谱可视化纹影摄影的使用

This manuscript outlines how to visualize mass spectrometry ambient ionization sources using schlieren photography. In order to properly optimize the mass ...

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of Phosphorus(I)

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable low-valent-phosphorus-containing compound acts as a useful P+ transfer agent. Unlike traditional methods employed to access low-coordinate phosphorus species which usually require pyrophoric phosphorus-containing precursors (white phosphorus, Tris(trimethylsilyl)phosphine, etc.), or harsh reducing agents (alkali metals, potassium graphite, etc.), the current approach does not involve pyrophoric or explosive reagents and can be done on large scales (&#62;20 g) in excellent yields by undergraduates with basic air-free synthetic training. The bromide counter ion is readily exchanged with other anions such as tetraphenyl borate (described herein) using typical salt metathesis reagents to obtain materials with desired properties and reactivities. The versatility of this P+ transfer approach is exemplified by the reactions of these triphosphenium precursors with an N-heterocyclic carbene and an anionic bisphosphine, each of which readily displace the neutral bisphosphine to give an NHC-stabilized phosphorus(I) cation and a phosphorus(I) containing zwitterion, respectively.

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI

The synthesis of a triphosphenium bromide salt is described and its use as a P+ transfer agent is outlined by reactions with an N-heterocyclic carbene and an anionic bisphosphine, yielding an NHC-stabilized P(I) cation and a P(I) containing zwitterion, respectively.

制备及反应性的Triphosphenium溴化物盐：磷方便稳定来源（I）

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable ...

Preparation of Chitosan-based Injectable Hydrogels and Its Application in 3D Cell Culture

The protocol presents a facile, efficient, and versatile method to prepare chitosan-based hydrogels using dynamic imine chemistry. The hydrogel is prepared by mixing solutions of glycol chitosan with a synthesized benzaldehyde terminated polymer gelator, and hydrogels are efficiently obtained in several minutes at room temperature. By varying ratios between glycol chitosan, polymer gelator, and water contents, versatile hydrogels with different gelation times and stiffness are obtained. When damaged, the hydrogel can recover its appearances and modulus, due to the reversibility of the dynamic imine bonds as crosslinkages. This self-healable property enables the hydrogel to be injectable since it can be self-healed from squeezed pieces to an integral bulk hydrogel after the injection process. The hydrogel is also multi-responsive to many bio-active stimuli due to different equilibration statuses of the dynamic imine bonds. This hydrogel was confirmed as bio-compatible, and L929 mouse fibroblast cells were embedded following standard procedures and the cell proliferation was easily assessed by a 3D cell cultivation process. The hydrogel can offer an adjustable platform for different research where a physiological mimic of a 3D environment for cells is profited. Along with its multi-responsive, self-healable, and injectable properties, the hydrogels can potentially be applied as multiple carriers for drugs and cells in future bio-medical applications.

Here we describe a facile preparation of chitosan-based injectable hydrogels using dynamic imine chemistry. Methods to adjust the hydrogel&#8217;s mechanical strength and its application in 3D cell culture are presented.

糖注射水凝胶的制备及其在3D 细胞培养中的应用

The protocol presents a facile, efficient, and versatile method to prepare chitosan-based hydrogels using dynamic imine chemistry. The hydrogel is ...

The MPLEx Protocol for Multi-omic Analyses of Soil Samples

Mass spectrometry (MS)-based integrated metaproteomic, metabolomic, and lipidomic (multi-omic) studies are transforming our ability to understand and characterize microbial communities in environmental and biological systems. These measurements are even enabling enhanced analyses of complex soil microbial communities, which are the most complex microbial systems known to date. Multi-omic analyses, however, do have sample preparation challenges, since separate extractions are typically needed for each omic study, thereby greatly amplifying the preparation time and amount of sample required. To address this limitation, a 3-in-1 method for the simultaneous extraction of metabolites, proteins, and lipids (MPLEx) from the same soil sample was created by adapting a solvent-based approach. This MPLEx protocol has proven to be both simple and robust for many sample types, even when utilized for limited quantities of complex soil samples. The MPLEx method also greatly enabled the rapid multi-omic measurements needed to gain a better understanding of the members of each microbial community, while evaluating the changes taking place upon biological and environmental perturbations.

A protocol is presented for simultaneously extracting metabolites, proteins, and lipids from a single soil sample, allowing reduced sample preparation times and enabling multi-omic mass spectrometry analyses of samples with limited quantities.

土壤样品多涨价可能分析的 MPLEx 协议

Mass spectrometry (MS)-based integrated metaproteomic, metabolomic, and lipidomic (multi-omic) studies are transforming our ability to understand and ...

Application of Elemental Lanthanides in the Selective C-F Activation of Trifluoromethylated Benzofulvenes Providing Access to Various Difluoroalkenes

The selective activation of one carbon-fluorine bond in polyfluorinated aromatic molecules or in trifluoromethyl-containing substrates offers the possibility of accessing unique fluorine-containing molecules, which are difficult to obtain by other synthetic pathways. Among various metals, which can undergo C-F activation, lanthanides (Ln) are good candidates as they form strong Ln-F bonds. Lanthanide metals are strong reducing agents with a redox potential Ln3+/Ln&#160;of approximately -2.3 V, which is comparable to the value of the Mg2+/Mg&#160;redox couple. In addition, lanthanide metals display a promising functional group tolerance and their reactivity can vary along the lanthanide series, making them suitable reagents for fine-tuning reaction conditions in organic and organometallic transformations. However, due to their oxophilicity, lanthanides react readily with oxygen and water and therefore require special conditions for storage, handling, preparation, and activation. These factors have limited a more widespread use in organic synthesis. We herein present how dysprosium metal - and by analogy all lanthanide metals - can be freshly prepared under anhydrous conditions using glovebox and Schlenk techniques. The freshly filed metal, in combination with aluminum chloride, initiates the selective C-F activation in trifluoromethylated benzofulvenes. The resulting reaction intermediates react with nitroalkenes to obtain a new family of difluoroalkenes.

This protocol describes the preparation of elemental lanthanides under inert atmosphere and their application in a selective C-F activation process involving trifluoromethylated benzofulvenes.