Freie Universität Berlin, Institut für Chemie und Biochemie, Takustrasse 3, D-14195 Berlin, Germany.
Beilstein J Org Chem. 2010 Dec 28;6:1229-45. doi: 10.3762/bjoc.6.141.
A series of γ-oxo esters suitably substituted with various styrene subunits was subjected to samarium diiodide-induced 8-endo-trig cyclizations. Efficacy, regioselectivity and stereoselectivity of these reactions via samarium ketyls strongly depend on the substitution pattern of the attacked alkene moiety. The stereoselectivity of the protonation of the intermediate samariumorganyl is also influenced by the structural features of the substrates. This systematic study reveals that steric and electronic factors exhibited by the alkene and ketone subunits are of high importance for the outcome of these cyclization reactions leading to highly substituted benzannulated cyclooctanol derivatives. In exceptional cases, 7-exo-trig cyclizations to cycloheptanol derivatives have been observed. In examples with high steric hindrance the ketyl-aryl coupling can be a competing process.
一系列适当取代的γ-氧代酯与各种苯乙烯亚基进行了钐二碘化物诱导的 8-endo-trig 环化反应。这些通过钐自由基引发的反应的功效、区域选择性和立体选择性强烈依赖于被攻击的烯烃部分的取代模式。中间体钐有机化合物的质子化的立体选择性也受到底物结构特征的影响。这项系统研究表明，烯烃和酮部分表现出的空间和电子因素对于导致高度取代的苯并环辛醇衍生物的这些环化反应的结果非常重要。在特殊情况下，观察到了 7-exo-trig 环化生成环庚醇衍生物。在具有高空间位阻的例子中，酮-芳基偶联可能是一个竞争过程。
