Stereochemistry Control in the Lewis Acid Mediated Lactonization Reaction of γ,δ-Epoxy-β-silyloxy Esters
作者:Kassoum Nacro、Liliane Gorrichon、Jean-Marc Escudier、Michel Baltas
DOI:10.1002/1099-0690(200111)2001:22<4247::aid-ejoc4247>3.0.co;2-w
日期:2001.11
ZnCl2-triggered lactonization reactions of γ,δ-epoxy-β-silyloxy esters with remote alkoxy groups (CH2)nOR (n = 2, 3), producing five- and/or six-membered ring lactones, have been investigated. Under such conditions, the regiochemistry of the reaction is governed by the cis or trans nature of the starting epoxy ester and also by its C(3) stereochemistry. An X-ray crystallographic structure of a γ-lactone
已经研究了 ZnCl2 引发的带有远程烷氧基 (CH2)nOR (n = 2, 3) 的 γ,δ-环氧-β-甲硅烷氧基酯的内酯化反应,产生了五元和/或六元环内酯。在这种条件下,反应的区域化学受起始环氧酯的顺式或反式性质以及其 C(3) 立体化学的控制。获得了 γ-内酯(化合物 24')的 X 射线晶体结构和所有 γ-内酯的 C(4) 碳化学位移的 13C NMR 相关性,并用于确定环氧化物开环的区域选择性。在解释结果时提出了一个机械假设,涉及作为常见中间体的氧碳鎓离子。