76-84-6Relevant articles and documents
Wiig
, p. 4742,4743, 4748 (1930)
West et al.
, p. 6269,6271 (1960)
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Morton,Stevens
, p. 2244,2246, 4028, 4030 (1931)
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Metal-Free Access to (Spirocyclic)Tetrahydro-β-carbolines in Water Using an Ion-Pair as a Superacidic Precatalyst
Ji, Liang,Jia, Zhenhua,Liu, Xiaoxiao,Loh, Teck-Peng,Zhang, Ting,Zhang, Zhenguo
, p. 2052 - 2057 (2022/02/10)
The unprecedented triarylcarbonium ion-pair-catalyzed Pictet-Spengler reaction of tryptamines with aromatic aldehydes and cyclic ketones in water was disclosed. Under metal-free conditions, diverse tetrahydro-β-carbolines and spirocyclic tetrahydro-β-carb
Nonheme Diiron Oxygenase Mimic That Generates a Diferric-Peroxo Intermediate Capable of Catalytic Olefin Epoxidation and Alkane Hydroxylation including Cyclohexane
Kaizer, József,Oloo, Williamson N.,Que, Lawrence,Szávuly, Miklós
, (2021/12/27)
Herein are described substrate oxidations with H2O2 catalyzed by [FeII(IndH)(CH3CN)3](ClO4)2 [IndH = 1,3-bis(2′-pyridylimino)isoindoline], involving a spectroscopically characterized (μ-oxo)(μ-1,2-peroxo)diiron(III) intermediate (2) that is capable of olefin epoxidation and alkane hydroxylation including cyclohexane. Species 2 also converts ketones to lactones with a decay rate dependent on [ketone], suggesting direct nucleophilic attack of the substrate carbonyl group by the peroxo species. In contrast, peroxo decay is unaffected by the addition of olefins or alkanes, but the label from H218O is incorporated into the the epoxide and alcohol products, implicating a high-valent iron-oxo oxidant that derives from O-O bond cleavage of the peroxo intermediate. These results demonstrate an ambiphilic diferric-peroxo intermediate that mimics the range of oxidative reactivities associated with O2-activating nonheme diiron enzymes.
C-H Activation by RuCo3O4Oxo Cubanes: Effects of Oxyl Radical Character and Metal-Metal Cooperativity
Amtawong, Jaruwan,Balcells, David,Handford, Rex C.,Skjelstad, Bastian Bjerkem,Suslick, Benjamin A.,Tilley, T. Don
, p. 12108 - 12119 (2021/08/20)
High-valent multimetallic-oxo/oxyl species have been implicated as intermediates in oxidative catalysis involving proton-coupled electron transfer (PCET) reactions, but the reactive nature of these oxo species has hindered the development of an in-depth understanding of their mechanisms and multimetallic character. The mechanism of C-H oxidation by previously reported RuCo3O4 cubane complexes bearing a terminal RuV-oxo ligand, with significant oxyl radical character, was investigated. The rate-determining step involves H atom abstraction (HAA) from an organic substrate to generate a Ru-OH species and a carbon-centered radical. Radical intermediates are subsequently trapped by another equivalent of the terminal oxo to afford isolable radical-trapped cubane complexes. Density functional theory (DFT) reveals a barrierless radical combination step that is more favorable than an oxygen-rebound mechanism by 12.3 kcal mol-1. This HAA reactivity to generate organic products is influenced by steric congestion and the C-H bond dissociation energy of the substrate. Tuning the electronic properties of the cubane (i.e., spin density localized on terminal oxo, basicity, and redox potential) by varying the donor ability of ligands at the Co sites modulates C-H activations by the RuV-oxo fragment and enables construction of structure-activity relationships. These results reveal a mechanistic pathway for C-H activation by high-valent metal-oxo species with oxyl radical character and provide insights into cooperative effects of multimetallic centers in tuning PCET reactivity.