Synthesis of nitrogen-containing heterocycles using exo- and endo-selective radical cyclizations onto enamides
作者:Tsuyoshi Taniguchi、Daigo Yonei、Masamichi Sasaki、Osamu Tamura、Hiroyuki Ishibashi
DOI:10.1016/j.tet.2008.01.016
日期:2008.3
predominantly gave 6-endo cyclization products. These results suggest that the exo or endo selectivity of radical cyclization onto the alkenic bond of enamides can be controlled by positional change of the carbonyl group. For an understanding of these selectivities, heat of formation for each transition state was calculated. 6-endo-Selective radical cyclization was applied to the radical cascade, enabling
研究了酰胺的羰基位置变化对Bu 3 SnH介导的烷基自由基环化导致五元,六元,七元和八元含氮杂环的影响。甲5-外型环化通常优选在6-内闭环在具有对烯酰胺酰基侧链的烷基中心系统,而具有的烷基基团中心相对的酰基侧链烯酰胺主要得到6-内环化产物。这些结果表明,exo或endo自由基环化到酰胺的烯键上的选择性可以通过羰基的位置变化来控制。为了理解这些选择性,计算了每个过渡态的形成热。将6-内-选择性自由基环化作用于自由基级联反应,从而实现了cylindricine骨架的简明合成。甲7-或8-内切烷基自由基环化,但是,在占优势的相应的6-或7-外切环闭合无论烯酰胺的羰基的位置变化的。