New General Method for Regio- and Stereoselective Allylic Substitution with Aryl and Alkenyl Coppers Derived from Grignard Reagents
New General Method for Regio- and Stereoselective Allylic Substitution with Aryl and Alkenyl Coppers Derived from Grignard Reagents
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DOI：
10.1021/jo802426g
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发表时间：
2009-03-06
影响因子：
3.6
通讯作者：
Kobayashi, Yuichi
中科院分区：
文献类型：
--
作者：
Kiyotsuka, Yohei;Katayama, Yuji;Kobayashi, Yuichi
以RMgBr和CuBr中心点Me_2S为配体，用吡啶甲酸烯丙酯和铜试剂实现了Sp（2）-碳试剂（芳基和烯基阴离子）的烯丙基取代，区域和立体选择性地得到了反S（N）2'产物.空间和电子因素的试剂和周围的烯丙基部分的亚甲基取代基的大小略有影响的选择性。该反应体系与烷基化试剂也相容。并将其应用于季中心的构建和（-）-倍半儿茶烯醇的合成。吡啶基的吸电子性质和原位生成的C（=O）-C5 H4 N与MgBr 2的螯合作用被认为是导致高取代效率的原因。
Allylic substitution with Sp(2)-carbon reagents (aryl and alkenyl anions) was realized by using allylic picolinates and copper reagents derived from RMgBr and CuBr center dot Me2S to afford anti S(N)2' products regio- and stereoselectively. Steric and electronic factors in the reagents and the size of the methylene substituents around the allylic moiety marginally affected the selectivity. The reaction system was compatible with alkyl reagents as well. Furthermore, the substitution was applied to construction of a quaternary center and synthesis of (-)-sesquichamaenol. Electron-withdrawing nature of the pyridyl group and chelation of the C(=O)-C5H4N to MgBr2 generated in situ were found to be responsible for the high efficiency of the substitution.