Formation of Enamines via Catalytic Dehydrogenation by Pincer-Iridium Complexes
Formation of Enamines via Catalytic Dehydrogenation by Pincer-Iridium Complexes
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钳铱配合物催化脱氢形成烯胺
DOI：
10.1021/acs.joc.9b02846
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Goldman, Alan S.
中科院分区：
文献类型：
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作者：
Lu, Yansong J.;Zhang, Xiawei;Malakar, Santanu;Krogh-Jespersen, Karsten;Hasanayn, Faraj;Goldman, Alan S.
发现二异丙基膦基取代的钳形配位铱催化剂对于简单叔胺脱氢得到烯胺比先前报道的二叔丁基膦基取代的物质显著更有效。研究还发现二异丙基膦基取代的配合物催化几种β-官能化叔胺脱氢生成相应的1，2-双官能化烯烃。二叔丁基膦基取代的物质对这样的底物是无效的;据推测，显著的差异可归因于二异丙基膦基取代的催化剂的较少拥挤。实验确定的动力学同位素效应结合基于DFT的分析支持一种脱氢机制，该机制涉及胺α-C-H键的初始预平衡氧化加成，然后是β-C-H键的速率决定消除。
Di-isopropylphosphino-substituted pincer-ligated iridium catalysts are found to be significantly more effective for the dehydrogenation of simple tertiary amines to give enamines than the previously reported di-t-butylphosphino-substituted species. It is also found that the di-isopropylphosphino-substituted complexes catalyze dehydrogenation of several β-functionalized tertiary amines to give the corresponding 1,2-difunctionalized olefins. The di-t-butylphosphino-substituted species are ineffective for such substrates; presumably, the marked difference is attributable to the lesser crowding of the di-isopropylphosphino-substituted catalysts. Experimentally determined kinetic isotope effects in conjunction with DFT-based analysis support a dehydrogenation mechanism involving initial pre-equilibrium oxidative addition of the amine α-C–H bond followed by rate-determining elimination of the β-C–H bond.