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首页> 外文期刊>Chemistry: A European journal >Two Independent Orthogonal Stereomutations at a Single Asymmetric Center: A Narcissistic Couple
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Two Independent Orthogonal Stereomutations at a Single Asymmetric Center: A Narcissistic Couple

机译：在单个不对称中心的两个独立正交立体化：自恋夫妇

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The energy barriers in our recently discovered Walden-type inversion of chlorophosphonium salts are similar to those for Cope rearrangements of caged cyclic hydrocarbons. Therefore, we have designed a molecular system that integrates the two processes, thereby producing the first embodiment of a chemical species that can undergo two entirely different and independent stereomutation mechanisms at the same nominal asymmetric center. Thus, the energy barrier to the rearrangement of 9-phenyl-9-phosphabarbaralane oxide, which is easily prepared by a new high-yielding synthesis, was found to be roughly 11 kcal mol~(-1). This value is in contrast to the parent barbaralane (7.3 kcalmol~(-1)) but in good agreement with our computational results for the rearrangement barriers. Crucially, in the corresponding chlorophosphonium derivative, two stereomutations occur simultaneously: a fast Cope rearrangement (barrier ≈12 kcalmol~(-1)) and a slow Walden-type inversion of the phosphorus center (barrier ≈21 kcalmol~(-1)). The computational model also revealed a relationship between the Cope rearrangement barrier and the bridgehead distance. The phenomenon of two independent and geometrically orthogonal stereomutations at a single asymmetric center provided important general insights into reaction pathway bifurcation, microscopic reversibility, and dynamic stereochemistry. This first example of coexisting alternative mechanisms that involve covalent bonds may encourage the design of new types of dynamic molecular structures.
机译：我们最近发现的氯代膦盐的沃尔登型反转中的能量障碍与笼式循环烃的应对重排的逆转器相似。因此，我们设计了一种集成这两个过程的分子系统，从而产生可以在相同的标称不对称中心进行两个完全不同和独立的立体化机制的化学物质的第一实施方案。因此，发现通过新的高产合成容易地制备的9-苯基-9-磷巴拉氨酸氧化物的能量屏障是大约11kcal mol〜（-1）的。该值与父律rArbaralane相反（7.3 kcalmol〜（-1）），但与我们的重新排列屏障的计算结果良好。至关重要的是，在相应的氯膦鎓衍生物中，两个立体化同时发生：快速应对重排（屏障≈12千瓦醇〜（-1））和磷中心的缓慢沃尔登型反演（屏障≈21kcalmol〜（-1）） 。计算模型还揭示了COPE重排屏障与桥头距离之间的关系。单个不对称中心的两个独立和几何正交立体化的现象提供了重要的一般见解，进入反应途径分叉，显微镜可逆性和动态立体化学。该共存涉及共价键的替代机制的第一示例可以鼓励设计新型动态分子结构。

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