A Hydride Migration Mechanism for the Mo‐Catalyzed Z ‐2‐Selective Isomerization of Terminal Alkenes
A Hydride Migration Mechanism for the Mo‐Catalyzed Z ‐2‐Selective Isomerization of Terminal Alkenes
复制标题
Mo催化Z-2-末端烯烃选择性异构化的氢化物迁移机理
DOI：
10.1002/cctc.202301052
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发表时间：
2023
期刊：
影响因子：
4.5
通讯作者：
Dobereiner, Graham E.
中科院分区：
文献类型：
--
作者：
Jenny, Sarah E.;Serviano, Juan M.;Nova, Ainara;Dobereiner, Graham E.
1-烯烃的催化单键异构化（转位）是一种新兴的Z-2-烯烃的制备方法。从机理上理解影响Z选择性的因素，将有助于设计选择性更高的催化剂。我们在这里提出了cis-Mo（CO）4（PCy 3）（哌啶）（3）的反应途径，该预催化剂对α烯烃的转座显示出高Z选择性（例如，1-辛烯至2-辛烯，18：1 Z：Eat 74%转化率）。反应途径和同位素标记的计算模型表明，异构化通过烯丙基（1，3-氢化物移位）途径发生，其中氧化加成offac-（CO）3 Mo（PCy 3）（η2-烯烃），然后通过氢化物/CO交换从一个位置（顺式烯丙基C3碳）迁移到另一个位置（顺式烯丙基C1碳）。氢化物迁移途径的计算势垒低于探索的替代机制（例如，改变烯丙基的立构规整度、烯丙基旋转）。据我们所知，这是第一个研究提出这样的氢化物迁移烯烃异构化。
The catalytic one‐bond isomerization (transposition) of 1‐alkenes is an emerging approach toZ‐2‐alkenes. Design of more selective catalysts would benefit from a mechanistic understanding of factors controllingZselectivity. We propose here a reaction pathway forcis‐Mo(CO)4(PCy3)(piperidine) (3), a precatalyst that shows highZselectivity for transposition of alpha olefins (e. g., 1‐octene to 2‐octene, 18 : 1Z:Eat 74 % conversion). Computational modeling of reaction pathways and isotopic labeling suggests the isomerization takes place via an allyl (1,3‐hydride shift) pathway, where oxidative addition offac‐(CO)3Mo(PCy3)(η2‐alkene) is followed by hydride migration from one position (cisto allyl C3carbon) to another (cisto allyl C1carbon) via hydride/CO exchanges. Calculated barriers for the hydride migration pathway are lower than explored alternative mechanisms (e. g., change of allyl hapticity, allyl rotation). To our knowledge, this is the first study to propose such a hydride migration in alkene isomerization.