Intramolecular Heck Couplings and Cycloisomerizations of Bromodienes and Enynes with 1′,1′-Disubstituted Methylenecyclopropane Terminators: Efficient Syntheses of [3]Dendralenes
作者:Stefan Bräse、Hanno Wertal nee Nüske、Daniel Frank、Denis Vidović、Armin de Meijere
DOI:10.1002/ejoc.200500330
日期:2005.10
atom-economic, palladium-catalyzed cycloisomerization. The vinylpalladium halide intermediate generated by initial carbopalladation of the 1,6-enyne 10-H with in situ generated phenylpalladium iodide also underwent the same cyclization cascade to yield the correspondingly phenyl-substituted cyclic [3]dendralene 41-Ph (21 %). The palladium-catalyzed cycloisomerization of the alk-1-ene-7,12-diyne 33-H gave the
具有四取代亚甲基环丙烷端基的 2-Bromoalka-1,n-二烯如 9、30 和 14(n = 7),在钯催化下,经过环丙烷开环环化得到 2-乙烯基-3-亚甲基-1-环烯烃 41 (n = 6)、42 (n = 7) 和 43,它们分别是取代的单环 [3] 树枝烯,产率分别为 65%、63% 和 70%。通过更原子经济的方法从相应的 1,6- (10-H, 15) 和 1,7-烯炔 (28-H) 中分离出相同的交叉共轭三烯,收率良好(77-92%) , 钯催化的环异构化。通过 1,6-烯炔 10-H 与原位生成的苯基碘化钯的初始碳钯化生成的乙烯基卤化钯中间体也经历了相同的环化级联反应,生成相应的苯基取代的环状 [3] 树枝状化合物 41-Ph (21 %)。1-烯-7,12-二炔 33-H 的钯催化环异构化得到双环交叉共轭四烯 50-H (43%)。使用专门设计的模型系统 20-H 证明