Novel Isomerically Pure Tetrasubstituted Allylboronates: Stereocontrolled Synthesis of α-Exomethylene γ-Lactones as Aldol-Like Adducts with a Stereogenic Quaternary Carbon Center
作者:Jason W. J. Kennedy、Dennis G. Hall
DOI:10.1021/ja016391e
日期:2002.2.1
1-alkoxycarbonyl vinylcopper(I) intermediates from the conjugate addition of organocuprates onto acetylenic esters were trapped with very high cis-addition selectivity with iodomethylboronic esters in the presence of HMPA. The resulting isomerically pure 3,3-disubstituted allylboronates react with aldehydes in a highly diastereo- and enantioselective manner, providing α-exomethylene γ-lactones with a stereogenic
尽管它们固有的异构化倾向和低反应性,1-烷氧基羰基乙烯基铜 (I) 中间体在 HMPA 存在下与碘甲基硼酸酯以非常高的顺式加成选择性捕获了有机铜酸盐与炔酸酯的共轭加成。所得的异构纯 3,3-二取代烯丙基硼酸酯以高度非对映选择性和对映选择性方式与醛反应,提供具有立体异构四元 β-碳中心的 α-外亚甲基 γ-内酯。