Methylenecyclopropanes (MCP) undergo ring opening reactions with group I and II metal halides and ammonium halides in liquid SO2 to afford homoallylic halides, which are versatile reagents in organic synthesis. The developed reaction conditions are compatible with acid-labile substrates such as N-Boc-protected compounds. Liquid SO2 is a polar reaction medium with Lewisacid properties that solubilizes
亚甲基环丙烷(MCP)与第一和第二族金属卤化物和卤化铵在液体SO 2中进行开环反应,得到均烯丙基卤化物,它们是有机合成中的通用试剂。所开发的反应条件与酸不稳定的底物如N -Boc保护的化合物相容。液体SO 2是具有路易斯酸性质的极性反应介质,可溶解无机盐。通过对照实验证明了SO 2的独特性质:1)在常规溶剂中与上述盐进行反应后,在催化量的H 3 PO 4(相似的pK)存在下也未观察到MCP开环a等于H 2 SO 3),或不存在H 3 PO 4;2)SO 2在THF中的溶液表现出与液体SO 2相似的性质。
Cyclopentane ring formation in the cycloaddition reaction of 3-alkenyl radicals to radicophilic olefins
作者:Radomir N. Saičić、Živorad Čeković
DOI:10.1016/s0040-4020(01)81532-5
日期:1990.1
well as of 5- -cyclization of intermediary 5-hexenyl type radical (), was achieved. The fate of intermediary cyclopentylmethyl radicals ( and ) depends on the nature of substituents attached to radical carbon. In case of alkyl groups (), the nucleophilic reactivity of radical intermediates was increased and an intermolecular addition reaction occurred with the formation of a new C-C bond. However, in
Ring-opening reaction of methylenecyclopropanes with LiCl, LiBr or NaI in acetic acid
作者:Jin-Wen Huang、Min Shi
DOI:10.1016/j.tet.2003.12.061
日期:2004.2
The methylenecyclopropanes 1 react with LiCl, LiBr or NaI at 80 °C to give the corresponding gem-disubstituted homoallylic halides 2 in good to excellent yields in aceticacid. In some cases, the ring-openingreaction can be completed within 5 min to give the corresponding gem-disubstituted homoallylic halides in high yields.
Ring-Opening Reactions of Methylenecyclopropanes Promoted by Metal Halides
作者:Bo Xu、Min Shi
DOI:10.1021/ol034142k
日期:2003.5.1
The methylenecyclopropanes (MCPs) react with various metal chlorides or bromides to give the corresponding homoallylic chlorides or bromides in good yields. [reaction: see text]
Homoallyl radical, e.g. , reacts with an electron-deficient olefinic bond with a new CC bond forming and arising of a 5-hexenyl radical which further undergoes to cyclization with a cyclopentane ring () annulation.