The inherently strained furan-fused cyclobutenes, in situ generated via cycloisomerizations of allenyl ketones bearing cyclopropyl moiety under gold catalysis, have been utilized as reactive building blocks toward cross cycloadditions. The [4 + 2] and [3 + 2] annulations of these species with benzo[c]isoxazoles and N-iminoquinazolinium ylides furnish various three-dimensional cyclobutane-bridged polyheterocycles
通过在金催化下通过带有环丙基部分的烯丙基酮的环异构化原位产生的固有应变的呋喃稠合的环丁烯已被用作朝向交叉环加成的反应性结构单元。这些物质与苯并[ c ]异恶唑和N-亚氨基喹唑啉鎓叶立德的[4 + 2]和[3 + 2]环以良好的收率提供各种三维环丁烷桥联的多杂环化合物。多种典型的电子不足的1,3-二烯,杂二烯和1,3-偶极子可以捕获呋喃稠合的环丁烯,从而提供多种多环结构。
1,2-Gold Carbene Transfer Empowers Regioselective Synthesis of Polysubstituted Furans
A gold-catalyzedcascade cycloisomerization/ring-opening reaction of allenyl ketones bearing a cyclopropyl moiety with a wide variety of alcohols or ketones is developed. This reaction involves an unprecedented 1,2-gold carbene transfer to provide regioselective and modular access to tri- or tetrasubstituted furans in moderate to high yields and with broad substrate tolerability.
Copper(I) Iodide Mediated Iodocyclization of Cyclopropylideneallenyl Ketones: Facile and Effective Synthesis of Highly Substituted Furan Derivatives
作者:Maozhong Miao、Xin Xu、Lijun Xu、Hongjun Ren
DOI:10.1002/ejoc.201402823
日期:2014.9
Electrophilic cyclization of cyclopropylideneallenyl ketones in the presence of I2/CuI offers an efficient and straightforward route to highly substituted furans under mild reaction conditions. Further transformation of the resulting iodofurans provides structurally more advanced furanderivatives.
A novel PdCl2-catalyzed oxidative cycloisomerization of 3-cyclopropylideneprop-2-en-1-ones, providing a facile synthesis of highly strained functionalized 2-alkylidenecyclobutanones via furan-fused cyclobutene intermediates, is reported. An interesting route to 2(3H)-furanones with a spiro-cyclopropane unit from the obtained 2-alkylidenecyclobutanones via a ring-contraction rearrangement reaction is
all-carbon 1,4-dipoles could be generated selectively from the gold(I)-catalyzed cycloisomerizations of allenyl ketones bearing a cyclopropyl moiety, which undergo [4 + 3] cycloadditions with nitrones to produce two regiomers of furan-condensed N,O-seven-membered rings in moderate to excellent yields highly selectively.