在五配位磷(PV)原子上亲核取代反应的立体化学机理很少研究。在这里,我们详细报告五配位氢螺膦与酚类化合物的Atherton-Todd型反应。通过31 P NMR示踪实验,X射线衍射分析和密度泛函理论计算,提出了在P–V原子处亲核取代的立体化学机理。Atherton-Todd型反应的第一步是形成卤代螺磷环烷中间体,并明确保留磷的构型。第二步是卤代螺旋磷烷在PV原子上的亲核取代反应。使用CCl 4时作为卤化剂,氯化螺磷烷的反应通过S N 2(PV )机理进行,而PCl键的背面进攻是主要途径。对于具有ΔP构型的氯化螺磷膦,通常会获得完全P转化的产物。对于具有P构型的P-Cl键具有更大空间位阻的ΛP构型的氯化螺磷烷,P保留产物的比例明显增加,并获得了一对非对映异构体。此外,如果将CBr 4用作卤化剂,则溴化螺正膦的亲核取代反应可能会通过S N 1(PV )机制产生一对非对映异构体。
The <sup>3</sup><i>J</i><sub>CCNP</sub> Coupling Constants of Pentacoordinate Spirophosphorane Derivatives: As a Method to Assign Relative Configuration
pentacoordinate spirophosphorane diastereoisomers, while the 2JCNP value remained almost unchanged. The 3JCCNP value of the spirophosphorane with ΛP configuration at phosphorus was obviously larger than that with ΔP configuration. The rule, 3JCCNP (ΛP) > 3JCCNP (ΔP), for pentacoordinate spirophosphorane diastereoisomers was used to assign the configurations of new alkoxy spirophosphorane derivatives,
The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI-MS<sup>n</sup>
作者:Xiaoyan Cui、Can Sun、Pei Zhao、Yanyan Wang、Yanchun Guo、Yufen Zhao、Shuxia Cao
DOI:10.1002/jms.4064
日期:2018.4
An electron‐withdrawing substituent at the ortho‐position always results in the removal of a corresponding phenol analogue, while cleavage by spiroring opening becomes the predominant fragmentation pathway if an electron‐donating substituent is at the phenolic group. The substituent effects on the competitive fragmentation pathways were further elucidated by theoretical calculations, single crystal
The Atherton–Todd-type reaction of pentacoordinate hydrospirophosphoranes synthesized from l-valine with phenols was first investigated. A series of new types of phenoxy spirophosphoranes were stereospecifically synthesized and a preliminary stereochemical mechanism was proposed by 31P NMR tracing experiments and X-ray diffraction analysis. The reaction proceeded via the initial generation of chlorinated