A Facile Synthesis of (n+3) and (n+4) Ring-Enlarged Lactones as well as of Spiroketolactones from n-Membered Cycloalkanones
作者:Alfred Hassner、Tarun Pradhan
DOI:10.1055/s-2007-990820
日期:2007.11
simple ethyl l-allyl-2-oxocycloalkanecarboxylates, resulting from a three-atom ring enlargement. Similarly, four-atom ring enlargements of a 5- to 9- and 6- to 10-membered-ring lactones were achieved. Alkoxy radical fragmentation (ARF) with hypervalent iodine was used as the key step for these ring expansions. The ring enlargement proceeds via an unstable hemiketal intermediate, which was isolable in some
:我们报告了从简单的 1-烯丙基-2-氧代环烷羧酸乙酯轻松合成功能化 8-、9-、10-、11-和 15 元环内酯的详细研究,这是由三原子环扩大产生的。类似地,实现了 5 至 9 和 6 至 10 元环内酯的四原子环扩大。具有高价碘的烷氧基自由基断裂(ARF)被用作这些环扩展的关键步骤。环扩大通过不稳定的半缩酮中间体进行,在某些情况下是可分离的。在未分离半缩酮的情况下,分子模型计算与羟基酮与半缩酮的相对稳定性一致。在与碘或溴反应时,相同的底物可以转移到离子途径中以提供螺内酯。