Facile Construction of Spirocyclopropanated Bi-, Tri- and Tetracyclic Skeletons by Novel Cascades Involving Intra- and Intermolecular Heck Reactions of 2-Bromo-1,6-enynes and Bicyclopropylidene
作者:Michael Schelper、Armin de Meijere
DOI:10.1002/ejoc.200400668
日期:2005.2
elevated temperatures (120−140 °C) the initially formed tetraenes underwent 6π-electrocyclization to give spiro[cyclopropane-1,4′-bicylo[4.3.0]-1(6),2-dienes] 21-R, 22-R and 23-R. This novel class of spirocyclopropanated oligocycles is also accessible by a one-pot protocol. The highest yields for both the tetraenes and bicyclo[4.3.0]nonadiene and its heteroanalogues were obtained with bulky substituents
在炔烃末端具有庞大取代基的无环 2-溴-1,6-烯炔 5-R、9-R 和 11-R 在 80°C 的钯催化下与高度紧张的双环亚丙基 (12) 共环化,得到交叉共轭四烯 13-R、18-R 和 19-R 的产率中等至良好 (34-71%)。只有 5-Ph 的共环化产生了额外的产物,它被确定为 11 元环 20。在升高的温度(120-140°C)下,最初形成的四烯经历 6π-电环化得到螺[环丙烷-1,4'-双环[4.3.0]-1(6),2-二烯] 21-R、22-R 和 23-R。这种新型的螺环丙烷化低聚环也可通过一锅法获得。四烯和双环的产率最高[4.3。0]壬二烯及其杂类似物在前体的炔末端具有大的取代基。含杂原子的前体 9-R 和 11-R 的产率低于其全碳类似物 5-R。无环 2-bromo-1,8-dien-6-ynes 28a,b,c 在钯催化下与双环亚丙基 (12) 在 110 °C