Studies on the Mechanism of B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>-Catalyzed Hydrostannylation of Propargylic Alcohol Derivatives
作者:Martins S. Oderinde、Michael G. Organ
DOI:10.1002/anie.201204060
日期:2012.9.24
Sleight of hydride: B(C6F5)3 catalyzes the hydrostannylation of propargylicalcohols in a regio‐ and stereoselective manner (see scheme). This Lewis acid first abstracts a hydride from the stannane, thus forming a borohydride/stannyl cation pair, the stability of which depends on solvent and ligands. Deuterium‐labeling experiments showed that the source that delivers a hydride to the alkenyl cation
氢化物的轻度:B(C 6 F 5)3以区域和立体选择性的方式催化炔丙醇的加氢甲锡化反应(参见方案)。该路易斯酸首先从锡烷中提取氢化物,从而形成硼氢化物/锡烷基阳离子对,其稳定性取决于溶剂和配体。氘标记实验表明,将氢化物传递至烯基阳离子的来源不是硼氢化物,而是锡烷的第二分子。
A New Insight into the Stereoelectronic Control of the Pd
<sup>0</sup>
‐Catalyzed Allylic Substitution: Application for the Synthesis of Multisubstituted Pyran‐2‐ones via an Unusual 1,3‐Transposition
作者:Zbyněk Brůža、Jiří Kratochvíl、Jeremy N. Harvey、Lubomír Rulíšek、Lucie Nováková、Jana Maříková、Jiří Kuneš、Pavel Kočovský、Milan Pour
DOI:10.1002/chem.201900323
日期:2019.6.18
Pyran‐2‐ones 3 undergo a novel Pd0‐catalyzed 1,3‐rearrangement to afford isomers 6. The reaction proceeds via an η2‐Pd complex, the pyramidalization of which (confirmed by quantum chemistry calculations) offers a favorable antiperiplanar alignment of the Pd−C and allylic C−O bonds (C), thus allowing the formation of an η3‐Pd intermediate. Subsequent rotation and rate‐limiting recombination with the
Cuprous Chloride Accelerated Stille Reactions. A General and Effective Coupling System for Sterically Congested Substrates and for Enantioselective Synthesis
作者:Xiaojun Han、Brian M. Stoltz、E. J. Corey
DOI:10.1021/ja991500z
日期:1999.8.1
of cuprous chloride as an accelerant for coupling. Thus, using a protocol for coupling that involves the system Pd(PPh3)4/CuCl/LiCl under anaerobic conditions in dimethylsulfoxidesolution at 60 °C, a wide variety of Stille coupling reactions which otherwise fail can be effected in excellent yield (Table 1). The process has been applied to the enantioselective synthesis of the chiral 1-(arylethyl)alkylcarbinol
Stille 偶联反应的一个主要限制来自空间筛选,特别是在乙烯基锡烷组分中。例如,由于非常缓慢的反应速率和竞争性电影取代,通常观察到 1-取代的乙烯基锡烷和芳基全氟烷烃磺酸盐或卤化物可以忽略不计或低产率。通过发现和应用氯化亚铜作为偶联促进剂,这个问题在目前的工作中得到了克服。因此,使用涉及 Pd(PPh3)4/CuCl/LiCl 系统在 60 °C 的二甲基亚砜溶液中的厌氧条件下的耦合协议,可以以优异的产率实现各种各样的 Stille 耦合反应,否则这些反应会失败(表1)。该工艺已应用于手性1-(芳乙基)烷基甲醇26的对映选择性合成,天然产物尼康酮的模型。氯化亚铜对Stille偶联的加速可以通过乙烯基锡烷→乙烯基铜(I)跨金属的干预来解释。
Cross-conjugated dienols 3 were satisfactorily obtained via the palladium-catalyzed coupling reaction of 2-iodo-2-alken-1-ol 6 with vinyl Grignard reagents.