Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates.
Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates.
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DOI：
10.1021/jacs.5b04034
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发表时间：
2015-06-24
影响因子：
15
通讯作者：
Chirik PJ
中科院分区：
文献类型：
--
作者：
Schmidt VA;Hoyt JM;Margulieux GW;Chirik PJ
芳基取代的双(亚氨基)吡啶钴二氮化合物(RPDI)CoN2是α,ω-二烯分子内[2π + 2π]环加成反应生成相应双环[3.2.0]庚烷衍生物的有效预催化剂。该反应在温和的热条件下与未活化的烯烃进行，同时耐受胺和醚官能团。反应的整体二阶速率定律，关于钴预催化剂和底物的一阶速率定律，结合电子顺磁共振（EPR）光谱研究确定了催化剂静止状态取决于预催化剂和二烯底物的特性。通过 EPR 光谱观察平面 S =1/2 κ3-双（亚氨基）吡啶钴烯烃和四面体 κ2-双（亚氨基）吡啶钴二烯配合物，并在后一种情况下进行结构表征。半稳定螯合物促进二氮钴和烯烃化合物中主要基于配体的单占据分子轨道（SOMO）转化为二烯中间体中基于金属的SOMO，促进C-C键形成氧化环化。还用 2,4,6-三环戊基取代的芳基建立了双（亚氨基）吡啶取代的结构-活性关系，从而优化了催化 [2π + 2π] 环加成反应。环戊基提供了足够开放的金属配位球，促进底物配位，同时保持足够大以促进具有挑战性的、限制周转的 C(sp3)–C(sp3) 还原消除。
Aryl-substituted bis(imino)pyridine cobalt dinitrogen compounds, (RPDI)CoN2, are effective precatalysts for the intramolecular [2π + 2π] cycloaddition of α,ω-dienes to yield the corresponding bicyclo[3.2.0]heptane derivatives. The reactions proceed under mild thermal conditions with unactivated alkenes, tolerating both amine and ether functional groups. The overall second order rate law for the reaction, first order with respect to both the cobalt precatalyst and the substrate, in combination with electron paramagnetic resonance (EPR) spectroscopic studies established the catalyst resting state as dependent on the identity of the precatalyst and diene substrate. Planar S =1/2 κ3-bis(imino)pyridine cobalt alkene and tetrahedral κ2-bis(imino)pyridine cobalt diene complexes were observed by EPR spectroscopy and in the latter case structurally characterized. The hemilabile chelate facilitates conversion of a principally ligand-based singly occupied molecular orbital (SOMO) in the cobalt dinitrogen and alkene compounds to a metal-based SOMO in the diene intermediates, promoting C–C bond-forming oxidative cyclization. Structure–activity relationships on bis(imino)pyridine substitution were also established with 2,4,6-tricyclopentyl-substituted aryl groups, resulting in optimized catalytic [2π + 2π] cycloaddition. The cyclopentyl groups provide a sufficiently open metal coordination sphere that encourages substrate coordination while remaining large enough to promote a challenging, turnover-limiting C(sp3)–C(sp3) reductive elimination.
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影响因子：
15
作者：
CANNELL, LG
通讯作者：
CANNELL, LG
影响因子：
15
作者：
Bowman, Amanda C.;Milsmann, Carsten;Chirik, Paul J.
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用氧化还原活性双（Imino）吡啶铁配合物氧化添加碳碳键。
影响因子：
15
作者：
Darmon JM;Stieber SC;Sylvester KT;Fernández I;Lobkovsky E;Semproni SP;Bill E;Wieghardt K;DeBeer S;Chirik PJ
通讯作者：
Chirik PJ
影响因子：
15
作者：
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通讯作者：
Corey, E. J.