7-endo selective aryl radical cyclization onto enamides leading to 3-benzazepines: concise construction of a cephalotaxine skeleton.
7-endo selective aryl radical cyclization onto enamides leading to 3-benzazepines: concise construction of a cephalotaxine skeleton.
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DOI：
10.1021/jo040264u
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发表时间：
2005-02
期刊：
影响因子：
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通讯作者：
T. Taniguchi;A. Ishita;M. Uchiyama;O. Tamura;O. Muraoka;G. Tanabe;H. Ishibashi*
中科院分区：
文献类型：
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作者：
T. Taniguchi;A. Ishita;M. Uchiyama;O. Tamura;O. Muraoka;G. Tanabe;H. Ishibashi*
Bu 3SnH介导的2-（2-溴苯基）-N-乙烯基乙酰胺的自由基环化得到6-外环化产物15作为主要产物，而N-[2-（2-溴苯基）乙基]-N-乙烯基酰胺几乎只得到7-内环化产物。这些结果表明，烯酰胺上羰基的位置对环化反应的进程起着重要的作用。采用7位内选择性环合反应，简洁地构建三尖杉碱骨架。
Bu3SnH-mediated radical cyclizations of 2-(2-bromophenyl)-N-ethenylacetamide gave 6-exo cyclization product 15 as the major product, whereas N-[2-(2-bromophenyl)ethyl]-N-ethenylamides gave almost exclusively 7-endo cyclization products. These results indicated that the position of the carbonyl group on enamide played an important role in deciding the course of the cyclization. The 7-endo selective cyclization was applied to concise construction of a cephalotaxine skeleton.