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首页> 美国卫生研究院文献>other >Structure/Reactivity Relationships in the Benzocphenanthrene Skeleton: Stable Ion and Electrophilic Substitution (Nitration Bromination) Study of Substituted Analogs; Novel Carbocations and Substituted Derivatives
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Structure/Reactivity Relationships in the Benzocphenanthrene Skeleton: Stable Ion and Electrophilic Substitution (Nitration Bromination) Study of Substituted Analogs; Novel Carbocations and Substituted Derivatives

机译：苯并c菲骨架的结构/反应性关系：取代类似物的稳定离子和亲电取代（硝化溴化）研究；新型碳正离子和取代衍生物

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A series of novel carbocations were generated by low temperature protonation of substituted benzo[c]phenanthrenes B[c]Phs and their charge delocalization pathways were elucidated by NMR based on the magnitude of Δδ13C values. It has been shown that the protonation regioselectivity is strongly controlled by methoxy and hydroxyl substituents, whose directive effects override methyl substitution effects. Regiocontrol by –OMe and –OH substituents, and its stronger influence relative to methyl groups, was also observed in the nitration and bromination reactions. Charge distribution modes in the regioisomeric protonated carbocations via parent B[c]Ph as well as in the benzylic carbocation formed via fjord-region epoxide ring opening were deduced by GIAO-DFT, and from the NPA-derived changes in charges over CHs. These patterns were compared with those derived from NMR experiments in the substituted derivatives. NMR-based charge delocalization mapping provided insight into structure/activity relationships in the methylated and fluorinated B[c]Phs. Regioselectivities observed in the nitration and bromination reactions in representative cases are the same as those via protonations. Among a group of novel nitro and bromo derivatives synthesized in this study are examples where nitro group is introduced into the fjord-region, for which X-ray structure could be obtained in one case.
机译：取代的苯并[c]菲B [c] Phs的低温质子化反应生成了一系列新型碳正离子，并根据Δδ 13 C的大小，通过NMR阐明了它们的电荷离域途径。已经表明，质子区域选择性受到甲氧基和羟基取代基的强烈控制，其指导作用优于甲基取代作用。在硝化和溴化反应中也观察到了–OMe和–OH取代基对区域的控制以及其相对于甲基的更强影响。 GIAO-DFT推导了通过母体B [c] Ph形成的区域异构质子化碳正离子中以及通过峡湾区环氧化物开环形成的苄基碳正离子中的电荷分布模式，以及NPA衍生的CHs电荷变化。将这些模式与由NMR实验得出的取代衍生物进行了比较。基于核磁共振的电荷离域图谱提供了对甲基化和氟化B [c] Phs中结构/活性关系的深入了解。在代表性案例中，在硝化和溴化反应中观察到的区域选择性与通过质子化的区域选择性相同。在这项研究中合成的一组新的硝基和溴衍生物中，有一些例子是将硝基引入峡湾区域，在这种情况下，可以在其中获得X射线结构。

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