A [4+4] annulation strategy for the synthesis of eight-membered carbocycles based on intramolecular cycloadditions of conjugated enynes
作者:Julia M. Robinson、Sami F. Tlais、Jennie Fong、Rick L. Danheiser
DOI:10.1016/j.tet.2011.09.031
日期:2011.12
processes. In the first step, the [4+2] cycloaddition of a conjugated enyne with an electron-deficient cyclobutene generates a strained six-membered cyclic allene that isomerizes to the corresponding 1,3-cyclohexadiene. In the second step, this bicyclo[4.2.0]octa-2,4-diene intermediate undergoes thermal or acid-promoted 6-electron electrocyclic ring opening to furnish a 2,4,6-cyclooctatrienone. The latter
据报道,用于合成八元碳环的 [4+4] 环化策略通过涉及两个周环过程的级联进行。在第一步中,共轭烯炔与缺电子环丁烯的 [4+2] 环加成生成应变的六元环状丙二烯,该丙二烯异构化为相应的 1,3-环己二烯。在第二步中,这种双环[4.2.0]octa-2,4-二烯中间体经历热或酸促进的6-电子电环开环以提供2,4,6-环辛三烯酮。后者的转变代表了酸促进 6 电子电环开环反应的第一个例子。