Catalyst versus Substrate Control of Forming ( E )-2-Alkenes from 1-Alkenes Using Bifunctional Ruthenium Catalysts
Catalyst versus Substrate Control of Forming ( E )-2-Alkenes from 1-Alkenes Using Bifunctional Ruthenium Catalysts
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使用双功能钌催化剂从 1-烯烃形成 (E)-2-烯烃的催化剂与底物控制
DOI：
10.1021/acs.oprd.8b00315
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发表时间：
2018
影响因子：
3.4
通讯作者：
Grotjahn, Douglas B.
中科院分区：
文献类型：
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作者：
Paulson, Erik R.;Delgado, Esteban;Cooksy, Andrew L.;Grotjahn, Douglas B.
在这里，我们详细研究了两种催化剂选择性地将 1-烯烃转化为 (E)-2-烯烃，同时限制过度异构化为 3-或 4-烯烃的能力。催化剂1和催化剂3分别由阳离子CpRu(κ2-PN)(CH3CN)+和Cp*Ru(κ2-PN)+（其中PN是双功能膦配体）和阴离子PF6–组成。具有 1 和 3 的六种底物的反应动力学模型生成一阶和二阶速率常数 sk1 和 k2（和 k3，如果适用），代表 1-烯烃转化为 (E)-2-烯烃 (k1)、(E)-2-烯烃转化为 (E)-3-烯烃 (k2) 的反应速率，依此类推。计算 k1:k2 比率以测量每种催化剂与每种底物发生单异构化的选择性。六种底物的 1 的 k1:k2 值范围为 32 至 132。 3 的 k1:k2 值明显更依赖于底物，对于除 5-hexen-2-one 之外的所有底物，其范围为 192 至 62000，其中 5-hexen-2-one 的 k1:k2 值仅为 4.7。比较每种底物的 1 和 3 的比率显示，在三种线性底物上使用 3 时，选择性提高了 6-12 倍，并且对于 5-甲基己-1-烯，选择性增加了 230 倍以上；对于甲硅烷基保护的 4-戊烯-1-醇 底物，选择性增加了 44 倍，这些底物分别远离烯烃 3 个和 5 个原子进行支化。底物5-hexen-2-one的独特之处在于1比3的选择性更高； NMR分析表明羰基氧的螯合可以促进过度异构化。这项工作强调了催化剂开发人员需要报告不同时间点催化反应的结果，并表明人们不仅需要考虑催化剂速率，还需要考虑所需产物（此处为 (E)-2-烯烃）保持完整的持续时间，其中对于标题反应，3 通常优于 1。
Here we examine in detail two catalysts for their ability to selectively convert 1-alkenes to (E)-2-alkenes while limiting overisomerization to 3- or 4-alkenes. Catalysts1and3are composed of the cations CpRu(κ2-PN)(CH3CN)+and Cp*Ru(κ2-PN)+, respectively (where PN is a bifunctional phosphine ligand), and the anion PF6–. Kinetic modeling of the reactions of six substrates with1and3generated first- and second-order rate constantsk1andk2(andk3when applicable) that represent the rates of reaction for conversion of 1-alkene to (E)-2-alkene (k1), (E)-2-alkene to (E)-3-alkene (k2), and so on. Thek1:k2ratios were calculated to produce a measure of selectivity for each catalyst toward monoisomerization with each substrate. Thek1:k2values for1with the six substrates range from 32 to 132. Thek1:k2values for3are significantly more substrate-dependent, ranging from 192 to 62 000 for all of the substrates except 5-hexen-2-one, for which thek1:k2value was only 4.7. Comparison of the ratios for1and3for each substrate shows a 6–12-fold greater selectivity using3on the three linear substrates as well as a>230-foldincrease for 5-methylhex-1-ene and a 44-fold increase for a silyl-protected 4-penten-1-ol substrate, which are branched three and five atoms away from the alkene, respectively. The substrate 5-hexen-2-one is unique in that1was more selective than3; NMR analysis suggested that chelation of the carbonyl oxygen can facilitate overisomerization. This work highlights the need for catalyst developers to report results for catalyzed reactions at different time points and shows that one needs to consider not only the catalyst rate but also the duration over which a desired product (here the (E)-2-alkene) remains intact, where3is generally superior to1for the title reaction.