Oxyphosphoranes with an oxaphospholene ring: analysis of the activation barriers of the isomerization process
Oxyphosphoranes with an oxaphospholene ring: analysis of the activation barriers of the isomerization process
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具有氧杂环磷烯环的氧正膦：异构化过程的活化障碍分析
DOI：
10.1021/ja00405a040
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发表时间：
1981
影响因子：
15
通讯作者：
J. Llinas
中科院分区：
文献类型：
--
作者：
G. Buono*;J. Llinas
通过三配位化合物如RP（OMe）_2（R= Me，Ph，CH= CH_2，SMe，CN，OMe，OPh，NMe_2）或Ph_2 POMe与丙二烯酮的反应，可以容易地得到含有环外双键和与磷键合的赤道sp_（12）碳的1，2-氧磷烯环的新氧膦。根据~（13）C和~（31）P核磁共振数据，推测了这些正膦的三角双锥（TBP）结构。用~ 1H-DNMR研究了规则交换过程，并通过计算机模拟交换模式得到了相应的活化自由焓。这些正膦的活化参数进行了比较与那些类似的正膦没有exocyclic doublebond上oxaphospholene环和sp3碳键合到磷。这些动力学参数解释的apicophilicity的ligandsand空间效应的假设，即较高的能量TBP拓扑异构体是积极接近的真实的过渡态的异构化途径。应用Holmes模型计算了两种可能的异构化途径的所有中间体的构象能，并找出了最可能的异构化途径。此外，还定量地评价了Me、Ph、CH= CH_2、NMe_2和OMe基团的相对亲顶性。CN和OPh配体与MeO基团相比表现出高的亲顶性，而SMe基团表现出相当的亲顶性。一个递减的apicophilicity规模的这些配体已经成立，似乎是更好地相关的诱导常数：比电负性。
New oxyphosphoranes containing a 1, 2-oxaphospholene ring with an exocyclic double bond and an equatorial sp1 2 carbon bonded to phosphorus are readily obtained by the reaction of tricoordinated compounds such as RP (OMe) 2 (R= Me, Ph, CH= CH2, SMe, CN, OMe, OPh, NMe2) or Ph2POMe with-allenic ketones. The trigonal-bipyramidal (TBP) structure of these phosphoranes is deduced from, 13C, and 31P NMR data. The regular exchangeprocesses were studied by'H DNMR, and the associated free enthalpy of activation was obtained by computer simulationof the exchange patterns. The activation parameters for these phosphoranes are compared with those of analogous phosphoranes without the exocyclic doublebond on the oxaphospholene ring and sp3 carbon bonded to phosphorus. These kinetic parameters are interpreted in terms of the apicophilicity of ligandsand steric effects within the assumption that the higher energy TBP topomer is energetically close to the real transition state of the isomerization pathway. Holmes’ model is applied to conformational energy calculations of all the intermediates of the twopossible isomerization pathways and allows us to find the most probable one. Furthermore the relative apicophilicityof Me, Ph, CH= CH2, NMe2, and OMe groups has been quantitatively evaluated. The CN and OPh ligands exhibit a high apicophilicity vs. the MeO group, while the SMe group presents a comparable one. A decreasing apicophilicity scale of these ligands has been set up and seems to be better correlated to the inductive constant: than electronegativity.