期刊
JOURNAL OF ORGANIC CHEMISTRY
卷 65, 期 9, 页码 2684-2695出版社
AMER CHEMICAL SOC
DOI: 10.1021/jo991742h
关键词
-
资金
- NCI NIH HHS [CA 74500-01A1] Funding Source: Medline
- NIGMS NIH HHS [GM60003-01] Funding Source: Medline
A highly effective method for the synthesis of the core indolo[2,3-a]quinolizidine skeleton found in yohimbine is described. The reaction of N-monosubstituted thioamides with bromoalkenoyl chlorides furnishes thioisomunchnones as transient 1,3-dipoles that undergo ready intramolecular cycloaddition across the tethered pi-bond to give thio-bicycloannulated products in a one-pot operation. The stereochemical outcome of the intramolecular reaction is the consequence of an endo cycloaddition of the neighboring-bond across the transient thioisomunchnone dipole. A major limitation of the method is that when a hydrogen is present in the alpha-position of the thioamide the initially formed thio-N-acyliminium ion undergoes proton loss to produce a S ,N-ketene acetal at a faster rate than dipole formation. Treatment of tetrahydro-beta-carboline-1-thione with 2-bromooct-7-enoyl chloride followed by reductive removal of sulfur from the cycloadduct resulted in the formation of (+/-)-alloyahimbanone. Attempts to cycloadd the thioisomunchnone dipole across several nucleophilic-bonds failed, and instead, products derived from cyclization of the pi-bond onto the initially formed thio-N-acyliminium ion were formed. The resulting N,S-ketals were further converted into several tetrahydroisoquinoline alkaloids in good yield.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据