Bromonium Ion Induced Transannular Oxonium Ion Formation−Fragmentation in Model Obtusallene Systems and Structural Reassignment of Obtusallenes V−VII
作者:D. Christopher Braddock、David S. Millan、Yolanda Pérez-Fuertes、Rebecca H. Pouwer、Richard N. Sheppard、Savade Solanki、Andrew J. P. White
DOI:10.1021/jo8026577
日期:2009.3.6
Ring-closing metathesis was used to construct the strained 11-membered ring of obtusallenes II (and IV). Bromonium ion induced transannular oxonium ion formation−fragmentation gave the macrocyclic carbon skeleton of obtusallene VII with a bromine atom at C-13, in line with a previously published hypothesis. An additional brominated [5.5.1]bicyclotridecane adduct that must arise from a bromonium ion induced transannular
闭环易位被用来构建应变的十二碳五烯二烯(和Ⅳ)的11元环。溴离子诱导的跨环氧鎓离子的形成-片段化形成了tus斯泰隆VII的大环碳骨架,C-13处带有溴原子,与先前发表的假设相符。还可以分离出额外的溴化[5.5.1]双环十三烷加合物,它必须由溴离子诱导的跨环氧鎓离子形成-碎片化而产生,这表明该加合物代表了尚未发现的天然产物的核心。obtusallene V的真实样品用NMR光谱研究,卤素中的C-7和C-13的位置被再分配一个的基础上,1313 C NMR氯诱导的同位素位移。随后通过X射线晶体学证实了该修饰的结构。这些发现使我们可以有把握地得出结论,ob二烯VII和VI的结构也应重新分配。
Epimeric Face-Selective Oxidations and Diastereodivergent Transannular Oxonium Ion Formation Fragmentations: Computational Modeling and Total Syntheses of 12-Epoxyobtusallene IV, 12-Epoxyobtusallene II, Obtusallene X, Marilzabicycloallene C, and Marilzabicycloallene D
作者:James Clarke、Karl J. Bonney、Muhammad Yaqoob、Savade Solanki、Henry S. Rzepa、Andrew J. P. White、David S. Millan、D. Christopher Braddock
DOI:10.1021/acs.joc.6b02008
日期:2016.10.21
bromoetherification. Epimeric face-selective oxidation of their Δ12,13 olefins followed by bromoallene installation allowed access to the oppositely configured 12,13-epoxides of 12-epoxyobtusallene II and 12-epoxyobtusallene IV. Subsequent exploration of their putative biomimetic oxonium ion formation–fragmentations reactions revealed diastereodivergent pathways giving marilzabicycloallene C and obtusallene