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首页> 外文期刊>Organometallics >Synthesis and Study of a Dialkylbiaryl Phosphine Ligand; Lessons for Rational Ligand Design
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Synthesis and Study of a Dialkylbiaryl Phosphine Ligand; Lessons for Rational Ligand Design

机译：二烷基亚烷基膦配体的合成与研究; 理性配体设计的课程

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摘要

The rational design and synthesis of a novel dialkylbiarylphosphine ligand, 2'-(dimethylphosphine)-2,6-dimethoxy-1,1'-biphenyl (MeSPhos), for palladium-catalyzed C-N cross-coupling reactions is described. Based on previous results, it was hypothesized that a ligand with electronic properties similar to (2-biphenyl)dimethylphosphine (MeJPhos) but with greater steric bulk would allow the cross-coupling of previously inaccessible deactivated aryl chlorides. As predicted, MeSPhos exhibited similar electronic properties to MeJPhos. However, MeSPhos surprisingly showed a significantly smaller steric profile than MeJPhos. In comparison to the widely used CySPhos (2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl), MeSPhos promoted the oxidative addition of highly deactived aryl chlorides for which CySPhos was ineffective, but significantly decreased the rate of reductive elimination. The kinetics of cross-coupling reactions showed that the altered steric and electronic parameters of MeSPhos had a significant impact on the rate of cross-coupling, and the decreased steric bulk had a profound deleterious impact on the catalyst stability. With regard to this latter point, only the most activated aryl chlorides reacted at a sufficient rate to overcome the rate of catalyst decomposition. These results indicate that the relationship between the electron-donating ability of the phosphine ligand and the rate of oxidative addition is complex, and they also illustrate that increasing substitution on the biphenyl structure does not necessarily increase the steric bulk of the ligand.
机译：描述了一种用于钯催化的C-N交联反应的新型二烷基均载氟膦配体，2' - （二甲基膦）-2,6-二甲氧基-1,1'-联苯（中间苯基）的合理设计和合成。基于先前的结果，可以推测，具有类似于（2-联苯基）二甲基（MeJPhos）电子性质，但具有更大的空间体积的配体将允许交叉偶联以前无法进入失活的芳基氯化物的。如预测，Mesphos向Mejphos表现出类似的电子特性。然而，Mesphos令人惊讶地显示出比Mejphos更小的空间曲线。与广泛使用的Cysphos（2-二环己基膦-2'，6'-二甲氧基苯基）相比，中间苯磺酸族促进了氧化剂添加的高度去移芳基氯化物，其中Cysphos无效，但是显着降低了减少消除速率。交叉偶联反应的动力学表明，MESPHOS的改变的空间和电子参数对交叉耦合速率产生了显着影响，并且降低的空间体对催化剂稳定性产生了深刻的有害影响。关于后一点，只有最活化的芳基氯以足够的速率反应以克服催化剂分解的速率。这些结果表明，膦配体的电子捐献能力与氧化添加率之间的关系是复合物的，并且它们还说明了越来越多的苯苯基结构取代不一定增加配体的空间大部分。

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