Stereocontrolled Synthesis of Heteroannular Acetals from Functionalized 1,5-Enynes via Radical Cascades—Construction of Quaternary and 1,2-Diquaternary Centres in Polycyclic Systems
作者:O Rhode、H.M.R Hoffmann
DOI:10.1016/s0040-4020(00)00592-5
日期:2000.8
Sequential, radical-mediated cyclizations of 1,5-enynes have been evaluated with respect to structure, stereochemistry and reactivity. In series A 5-exo-trig, 6-endo-dig cascades are favoured. The unusual 6-endo-dig cyclization is dictated by ring strain. Diastereomeric series B tolerates leakage into the 5-exo-trig, 5-exo-dig sequence, especially if a quaternary carbon centre is established during
关于结构,立体化学和反应性,已经评估了1,5-烯炔的自由基自由基介导的环化反应。在系列A中,偏爱5- exo- trig,6- endo- dig级联。不寻常的6-内切-环化是由环应变决定的。非对映体系列B容许泄漏到5- exo- trig,5- exo- dig序列中,特别是如果在第一个五环环化过程中建立了季碳中心的话。级联允许在单个会聚步骤中构建四个或更多个手性中心。还评估了烯烃组分E / Z几何形状的影响。