Bioinspirierte Nicht‐Häm‐Eisenoxidationskatalyse: Beteiligung von Oxoeisen(V)‐Oxidantien an der Spaltung starker C‐H‐Bindungen

Kal, Subhasree; Xu, Shuangning; Que, Lawrence

doi:10.1002/ange.201906551

Cited by 13 publications

(1 citation statement)

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“…An attractive approach to address this challenge is the direct catalytic amination of organic molecules and has been the subject of intense research efforts. − Nevertheless, most synthetic procedures involve toxic, explosive and/or expensive chemicals and intermediates and, therefore, are not in line with the principles of green chemistry . Inspired by the widely studied iron-based enzymes, biomimetic complexes have opened new avenues for the oxidation and amination of organic substrates. − However, most of the methods developed thus far lead to the installation of a protected form of the amino group, requiring additional and often challenging protecting group manipulations . Moreover, synthesis of unprotected amino functionality poses another serious challenge of product coordination to the metal catalysts, thereby, leading to catalyst deactivation.…”

Section: Introductionmentioning

confidence: 99%

A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N–O Reagent as the “Amino” Source and “Oxidant”

et al. 2022

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Herein, we study the mechanism of iron-catalyzed direct synthesis of unprotected aminoethers from olefins by a hydroxyl amine derived reagent using a wide range of analytical and spectroscopic techniques (Mössbauer, Electron Paramagnetic Resonance, Ultra-Violet Visible Spectroscopy, X-ray Absorption, Nuclear Resonance Vibrational Spectroscopy, and resonance Raman) along with high-level quantum chemical calculations. The hydroxyl amine derived triflic acid salt acts as the “oxidant” as well as “amino” group donor. It activates the high-spin Fe(II) ( S t = 2) catalyst [Fe(acac) 2 (H 2 O) 2 ] ( 1 ) to generate a high-spin ( S t = 5/2) intermediate ( Int I ), which decays to a second intermediate ( Int II ) with S t = 2. The analysis of spectroscopic and computational data leads to the formulation of Int I as [Fe(III)(acac) 2 - N -acyloxy] (an alkyl-peroxo-Fe(III) analogue). Furthermore, Int II is formed by N–O bond homolysis. However, it does not generate a high-valent Fe(IV)(NH) species (a Fe(IV)(O) analogue), but instead a high-spin Fe(III) center which is strongly antiferromagnetically coupled ( J = −524 cm –1 ) to an iminyl radical, [Fe(III)(acac) 2 -NH·], giving S t = 2. Though Fe(NH) complexes as isoelectronic surrogates to Fe(O) functionalities are known, detection of a high-spin Fe(III)- N -acyloxy intermediate ( Int I ), which undergoes N–O bond cleavage to generate the active iron–nitrogen intermediate ( Int II ), is unprecedented. Relative to Fe(IV)(O) centers, Int II features a weak elongated Fe–N bond which, together with the unpaired electron density along the Fe–N bond vector, helps to rationalize its propensity for N -transfer reactions onto styrenyl olefins, resulting in the overall formation of aminoethers. This study thus demonstrates the potential of utilizing the iron-coordinated nitrogen-centered radicals as powerful reactive intermediates in catalysis.

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Section: Introductionmentioning

confidence: 99%

A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N–O Reagent as the “Amino” Source and “Oxidant”

et al. 2022

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C−H Activation by an Iron‐Nitrido Bis‐Pocket Porphyrin Species

Wang

Zheng

et al. 2021

Angewandte Chemie

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High‐valent iron‐nitrido species are nitrogen analogues of iron‐oxo species which are versatile reagents for C−H oxidation. Nonetheless, C−H activation by iron‐nitrido species has been scarcely explored, as this is often hampered by their instability and short lifetime in solutions. Herein, the hydrogen atom transfer (HAT) reactivity of an Fe porphyrin nitrido species (2 c) toward C−H substrates was studied in solutions at room temperature, which was achieved by nanosecond laser flash photolysis (LFP) of its FeIII‐azido precursor (1 c) supported by a bulky bis‐pocket porphyrin ligand. C−H bonds with bond dissociation enthalpies (BDEs) of up to ≈84 kcal mol−1 could be activated, and the second‐order rate constants (k2) are on the order of 102–104 s−1 m−1. The Fe‐amido product formed after HAT could further release ammonia upon protonation.

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Chemoselective Oxyfunctionalization of Functionalized Benzylic Compounds with a Manganese Catalyst

et al. 2022

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Whilst allowing for easy access to synthetically versatile motifs and for modification of bioactive molecules, the chemoselective benzylic oxidation reactions of functionalized alkyl arenes remain challenging. Reported in this study is a new non-heme Mn catalyst stabilized by a bipiperidine-based tetradentate ligand, which enables methylene oxidation of benzylic compounds by H 2 O 2 , showing high activity and excellent chemoselectivity under mild conditions. The protocol tolerates an unprecedentedly wide range of functional groups, including carboxylic acid and derivatives, ketone, cyano, azide, acetate, sulfonate, alkyne, amino acid, and amine units, thus providing a low-cost, more sustainable and robust pathway for the facile synthesis of ketones, increase of complexity of organic molecules, and late-stage modification of drugs.

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Bioinspirierte Nicht‐Häm‐Eisenoxidationskatalyse: Beteiligung von Oxoeisen(V)‐Oxidantien an der Spaltung starker C‐H‐Bindungen

Cited by 13 publications

References 129 publications

A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N–O Reagent as the “Amino” Source and “Oxidant”

A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N–O Reagent as the “Amino” Source and “Oxidant”

C−H Activation by an Iron‐Nitrido Bis‐Pocket Porphyrin Species

Chemoselective Oxyfunctionalization of Functionalized Benzylic Compounds with a Manganese Catalyst

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