• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Synthesis and Reactivity of Six-Membered Oxa-Nickelacycles:A Ring-Opening Reaction of Cyclopropyl Ketones
【24h】

Synthesis and Reactivity of Six-Membered Oxa-Nickelacycles:A Ring-Opening Reaction of Cyclopropyl Ketones

机译：六元氧杂环丁烷环的合成与反应：环丙基酮的开环反应

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Cyclopropanecarboxalde-hyde (ha), cyclopropyl methyl ketone(lb), and cyclopropyl phenyl ketone(1c) were reacted with [Ni(cod)2](cod =1,5-cyclooctadiene) and PBu3 at100°C to give if-enonenickel com-plexes (2a–c). In the presence of PCy3(Cy = cyclohexyl), la and lb reactedwith [Ni(cod)2] to give the correspond-ing R-12:11-enonenickel complexes (3a,3b). However, the reaction of lc underthe same reaction conditions gave amixture of 3c and cyclopentane deriva-tives (4c, 4c'), that is, a [3+2] cycload-dition product of 1c with (E)-1-phenyl-but-2-en-l-one, an isomer of lc. In thepresence of a catalytic amount of [Ni-(cod)2] and PCy3, [3+2] homo-cycload-dition proceeded to give a mixture of4c (76%) and 4c' (17%). At roomtemperature, a possible intermediate,6 c, was observed and isolated by repre-cipitation at –20°C. In the presence of1,3-bis(2,6-diisopropylphenyl)imidazol- 2-ylidene (IPr), both l a and lc rapidlyunderwent oxidative addition tonickel(0) to give the corresponding six-membered oxa-nickelacycles (6ai, 6ci).On the other hand, lb reacted withnickel(0) to give the corresponding la-1124-enonenickel complex (3bi). Themolecular structures of 6ai and 6ciwere confirmed by X-ray crystallogra-phy. The molecular structure of 6aishows a dimeric -nickelenolate struc-ture. However, the molecular structureof 6ci shows a monomeric 1-11-nickel-enolate structure, and the nickel(II) 14-electron center is regarded as having"an unusual T-shaped planar" coordi-nation geometry. The insertion ofenones into monomeric if -nickeleno-late complexes 6c and 6ci occurred at room temperature to generate 13-oxa-allylnickel complexes (8, 9), whereasinsertion into dimeric 111-nickelenolatecomplex 6ai did not take place. Thediastereoselectivity of the insertion ofan enone into 6c having PCy3 as aligand differs from that into 6ci havingIPr as a ligand. In addition, the stereo-chemistry of 113-oxa-allylnickel com-plexes having IPr as a ligand is re-tained during reductive elimination toyield the corresponding [3+2] cycload-dition product, which is consistent withthe diastereoselectivity observed in Ni°/IPr-catalyzed [3+2] cycloaddition reac-tions of cyclopropyl ketones withenones. In contrast, reductive elimina-tion from the i'-oxa-allylnickel havingPCy3 as a ligand proceeds with inver-sion of stereochemistry. This is proba-bly due to rapid isomerization betweensyn and anti isomers prior to reductiveelimination.
机译：在100°C下，将环丙烷甲酸酐（ha），环丙基甲基酮（lb）和环丙基苯基酮（1c）与[Ni（cod）2]（cod = 1,5-cyclooctadiene）和PBu3反应，得到if-烯镍复杂（2a–c）。在PCy3（Cy ＝环己基）的存在下，Ia和Ib与[Ni（cod）2]反应，得到相应的R-12：11-烯镍配合物（3a，3b）。然而，在相同反应条件下1c的反应产生了3c和环戊烷衍生物（4c，4c'）的混合物，即1c与（E）-1-苯基-的[3 + 2]环合产物。 but-2-en-1-one，lc的异构体。在催化量的[Ni-（cod）2]和PCy 3的存在下，进行[3 + 2]均杂环，得到4c（76％）和4c′（17％）的混合物。在室温下，观察到可能的中间体6 c，并通过在–20°C下再沉淀分离。在存在1，，3-双（2,6-二异丙基苯基）咪唑-2-亚烷基（IPr）的情况下，Ia和Lc都迅速进行镍（0）的氧化加成反应，得到相应的六元氧杂-镍环（6ai，6ci）另一方面，1b与镍（0）反应得到相应的la-1124-烯镍配合物（3bi）。 X射线晶体学证实了6ai和6ci的分子结构。 6ai的分子结构显示了二聚体-尼克酸结构。然而，6ci的分子结构显示出单体的1-11-镍-烯酸酯结构，并且镍（II）14-电子中心被认为具有“异常的T形平面”协调几何形状。如果在室温下将烯酮插入单体if-镍-elelate-配合物6c和6ci，以生成13-氧杂-烯丙基镍配合物（8、9），而没有插入二聚体111-nickelenolate-配合物6ai。烯酮插入以PCy3为配体的6c的非对映选择性不同于以IPr为配体的6ci的非对映选择性。此外，在还原消除过程中，保留了具有IPr作为配体的113-氧杂烯丙基镍配合物的立体化学，得到了相应的[3 + 2]环化产物，这与Ni°中观察到的非对映选择性一致/ IPr催化的环丙基酮与烯酮的[3 + 2]环加成反应。相反，具有PCy3作为配体的i'-氧杂-烯丙基镍的还原消除反应进行立体化学反应。这很可能是由于还原消除前顺式异构体和反式异构体之间的快速异构化。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号