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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >New insights into addition reactions of dialkylzinc reagents to trifluoromethyl ketones: Structural authentication of a beta-hydride elimination product containing a tetranuclear zinc chain
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New insights into addition reactions of dialkylzinc reagents to trifluoromethyl ketones: Structural authentication of a beta-hydride elimination product containing a tetranuclear zinc chain

机译：二烷基锌试剂与三氟甲基酮加成反应的新见解：含有四核锌链的β-氢化物消除产物的结构鉴定

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A systematic study of the stoichiometric alkylation reactions of 2,2,2-trifluoroacetophenone 1 with [ZnR2(TMEDA)] (R = Me, Et, Bu-t, CH2SiMe3; TMEDA = N, N, N', N'-tetramethylethylenediamine) monitored by H-1 and F-19 NMR spectroscopy is presented. For R = Me, Et the alkylation products alkyl(alkoxides) [(TMEDA)Zn(R){OC(CF3)(R)Ph}] (R = Me, 2: Et, 3) are obtained as the single products of the reaction. When the steric bulk of the dialkylzinc reagent is increased the alkylation reaction is inhibited. Thus, for R = Bu-t, the reduction product [(TMEDA)Zn(Bu-t){OC(CF3)(H)Ph}] is obtained as a result of beta-hydride elimination from one of the tBu groups of the organometallic reagent. H-1 NMR spectroscopic monitoring of the reaction allowed the detection of isobutene as a side product of this reduction process. For the highly sterically demanding group R = CH2SiMe3 which lacks hydrogen atoms at the beta position, no reaction is observed even under refluxing conditions. Two important intermediates from these reactions have been structurally elucidated: [(TMEDA)Zn(Me){OC(CF3)(Me)Ph}] (2) which could be involved in the previously reported alkylation reaction of trifluoromethyl ketones by ZnR2 catalysed by TMEDA and unprecedented tetranuclear [(Bu-t)(2)Zn-4{OC(CF3)(H)Ph}(6)] (5) resulting from the reduction of 1 when reacted with (Bu2Zn)-Bu-t, which displays a rare Zn...Zn...Zn...Zn linear chain arrangement for a zinc alkyl(alkoxide).
机译：2,2,2-三氟苯乙酮1与[ZnR2（TMEDA）]的化学计量烷基化反应的系统研究（R = Me，Et，Bu-t，CH2SiMe3; TMEDA = N，N，N'，N'-四甲基乙二胺提出了通过H-1和F-19 NMR光谱监测的）。对于R = Me，Et烷基化产物烷基（烷氧化物）[（TMEDA）Zn（R）{OC（CF3）（R）Ph}]（R = Me，2：Et，3）作为反应。当二烷基锌试剂的空间体积增加时，烷基化反应受到抑制。因此，对于R = Bu-t，由于β-氢化物从其中一个tBu基团中被消除，获得了还原产物[（TMEDA）Zn（Bu-t）{OC（CF3）（H）Ph}]。有机金属试剂。反应的H-1 NMR光谱监测允许检测异丁烯作为该还原过程的副产物。对于具有高度空间要求的基团R = CH2SiMe3，该基团在β位缺少氢原子，即使在回流条件下也未观察到反应。已从结构上阐明了来自这些反应的两个重要中间体：[（TMEDA）Zn（Me）{OC（CF3）（Me）Ph}]（2），这可能与以前报道的三氟甲基酮通过ZnR2催化的烷基化反应有关。 TMEDA和史无前例的四核[（Bu-t）（2）Zn-4 {OC（CF3）（H）Ph}（6）]（5）与（Bu2Zn）-Bu-t反应时还原为1，它显示了一种稀有的Zn ... Zn ... Zn ... Zn线性链状排列的烷基锌（烷氧化物）。

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