Intramolecular 4 + 3 Cycloadditions. The Synthesis of Cyclooctanoids
作者:Michael Harmata、Saleh Elahmad、Charles L. Barnes
DOI:10.1021/jo00085a005
日期:1994.3
The synthesis of fused cyclooctanoids from the products of intramolecular 4 + 3 cycloaddition of cyclic oxyallylic and alkoxyallylic cations is described.
Intramolecular 4 + 3 Cycloadditions. Cycloaddition Reactions of Cyclic Alkoxyallylic and Oxyallylic Cations
作者:Michael Harmata、Saleh Elomari、Charles L. Barnes
DOI:10.1021/ja952740r
日期:1996.1.1
larger amounts of cycloadduct derived from extended (exo) transition states. This has been rationalized on the basis of ring strain in the endo transition states in this series. Cyclodecenyl oxyallylic cations are sickle-shaped and stereoselectively undergo cycloadditionviaextendedtransition states to a furan diene tethered by three carbons. Cyclododecenyl oxyallylic cations behave similarly, although
已经研究了氧烯丙基和烷氧基烯丙基阳离子的分子内 4 + 3 环加成。通过三或四个碳链与呋喃相连的环戊烯氧基烯丙基阳离子通过类似于分子间环加成反应的紧凑(内)过渡态以高立体选择性反应。六至八元氧烯丙基阳离子的反应不同,并产生越来越多的来自扩展(外)过渡态的环加合物。这已经根据本系列中内向过渡态中的环应变进行了合理化。环癸烯氧基烯丙基阳离子呈镰刀形,立体选择性地通过扩展过渡态发生环加成反应,生成由三个碳原子连接的呋喃二烯。环十二碳烯氧基烯丙基阳离子的行为相似,尽管证据表明也形成了少量的 W 型阳离子。环状烷氧基烯丙基砜在用 TiCl4 处理后产生相应的阳离子,后者产生环加合物......