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Comparative investigation of the reactivities between catalysts [Cp*RhCl2]2 and [Cp*IrCl2]2 in the oxidative annulation of isoquinolones with alkynes: a combined experimental and computational study
Organic Chemistry Frontiers ( IF 5.4 ) Pub Date : 2017-08-28 00:00:00 , DOI: 10.1039/c7qo00586e
Chaoyue Zhao 1, 2, 3, 4, 5 , Qingmei Ge 3, 4, 5, 6, 7 , Baiquan Wang 3, 4, 5, 6, 7 , Xiufang Xu 1, 2, 3, 4, 5
Affiliation  

The mechanisms and reactivities of the [Cp*RhCl2]2 and [Cp*IrCl2]2 catalyzed oxidative annulation reaction of isoquinolones with alkynes have been investigated by combined experimental and computational studies. The results have disclosed that the low reactivity of [Cp*IrCl2]2 is attributed to the electron-richness and low electronegativity of Ir(III). These factors make Ir(III) difficult to reduce to Ir(I) and thus lead to a high activation energy of the reductive elimination step. The electronic and steric effects of alkyne substituents on the reactivities have been investigated. Small-sized and strong electron-donating substituents on alkynes should enhance the reactivity of the reaction for both catalysts by not only avoiding the steric repulsion between substrates but also facilitating the reductive elimination. The rate-determining steps for reactions involving [Cp*RhCl2]2 and [Cp*IrCl2]2 are alkyne insertion and reductive elimination, respectively. When an alkyne bearing a small-sized and strong electron-donating substituent NMe2 is employed as a substrate, C–H activation becomes rate determining for both catalysts.

中文翻译:

异喹诺酮与炔烃氧化环化反应中催化剂[Cp * RhCl 2 ] 2和[Cp * IrCl 2 ] 2的反应性的比较研究:组合实验和计算研究

通过结合实验和计算研究,研究了[Cp * RhCl 2 ] 2和[Cp * IrCl 2 ] 2催化异喹诺酮与炔烃的氧化环化反应的机理和反应性。结果已经公开了[Cp * IrCl 2 ] 2的低反应性归因于Ir(III)的电子富集性和低电负性。这些因素使Ir(III)难以还原为Ir(I),因此导致还原消除步骤的活化能较高。已经研究了炔烃取代基对反应性的电子和空间效应。炔烃上的小且强的供电子性取代基不仅可以避免底物之间的空间排斥,而且还可以促进还原反应,从而可以提高两种催化剂的反应活性。涉及[Cp * RhCl 2 ] 2和[Cp * IrCl 2 ] 2的反应的速率确定步骤分别是炔烃插入和还原消除。当炔烃带有小且强的给电子取代基NMe 2时 如果将其用作底物,则C–H活化将决定两种催化剂的速率。
更新日期:2017-09-04
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