Switching the <i>N</i>‐Alkylation of Arylamines with Benzyl Alcohols to Imine Formation Enables the One‐Pot Synthesis of Enantioenriched α‐<i>N</i>‐Alkylaminophosphonates

Hofmann, Natalie; Hultzsch, Kai C.

doi:10.1002/ejoc.201900209

Cited by 33 publications

(21 citation statements)

References 103 publications

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“…In 2019, Hultzsch and Hofmann described the possibility to switch between the N ‐alkylation of anilines with benzyl alcohols and their dehydrogenative condensation in presence of complex 7 a , depending upon the reaction conditions (Scheme 27). [118] The amination products were obtained selectively in high yields when the reaction was carried out in a closed vessel under argon atmosphere, while the dehydrogenated products were obtained in an open system in air at high temperature. It was emphasized that in case of open system in air, an oxidative quenching of the activated Knölker complex 3 a (the reduction catalyst) occurs by oxygen under the reaction conditions, which bypasses the imine hydrogenation pathway.…”

Section: Alkylation Reactionsmentioning

confidence: 99%

(Cyclopentadienone)iron Complexes: Synthesis, Mechanism and Applications in Organic Synthesis

Akter

Anbarasan

2021

Chemistry An Asian Journal

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(Cyclopentadienone)iron tricarbonyl complexes are catalytically active, inexpensive, easily accessible and air‐stable that are extensively studied as an active pre‐catalyst in homogeneous catalysis. Its versatile catalytic activity arises exclusively due to the presence of a non‐innocent ligand, which can trigger its unique redox properties effectively. These complexes have been employed widely in (transfer)hydrogenation (e. g., reduction of polar multiple bonds, Oppenauer‐type oxidation of alcohols), C−C and C−N bond formation (e. g., reductive aminations, α‐alkylation of ketones) and other synthetic transformations. In this review, we discuss the remarkable advancement of its various synthetic applications along with synthesis and mechanistic studies, until February 2021.

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Section: Alkylation Reactionsmentioning

confidence: 99%

(Cyclopentadienone)iron Complexes: Synthesis, Mechanism and Applications in Organic Synthesis

Akter

Anbarasan

2021

Chemistry An Asian Journal

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“…Very recently, Hultzsch and Hofmann demonstrated the possibility to switch between HB‐type reactivity and oxidative reactions by simply modifying the experimental conditions (Scheme A) . The reaction of benzylic alcohols with various amines in the presence of pre‐catalyst 3aa and molecular sieves gave high yields of the amination products ( 14 ) when performed in a closed vessel under argon.…”

Section: Applications In Reactions Involving Ht Stepsmentioning

confidence: 99%

“…Effect of the reaction conditions on the outcome of alcohol amination (A), and proposed mechanism of the aerobic quench of catalyst 2a (B) …”

Section: Applications In Reactions Involving Ht Stepsmentioning

confidence: 99%

Recent Catalytic Applications of (Cyclopentadienone)iron Complexes

Pignataro

Gennari

2020

Eur J Org Chem

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(Cyclopentadienone)iron complexes (CICs) are attractive pre‐catalysts due to their easy preparation and robustness, which are uncommon features in homogeneous iron catalysis. They represent a striking example of how deeply a non‐innocent ligand may affect the catalytic properties of the metal. Swinging between the cyclopentadienone and the hydroxycyclopentadienyl form, the ligand induces iron to engage in H2 heterolytic cleavage and transfer. The latter represents the basis for numerous applications of CICs in redox chemistry (multiple bond reduction, alcohol oxidation) and “hydrogen borrowing” processes (e.g., alcohol amination) that have been reported over the last few years. Moreover, very recently catalytic applications of CICs in different types of reactivity (where again the non‐innocent ligand plays a key role), have appeared in the literature. This minireview summarizes the advancements that have been made in the field of CICs and their catalytic applications in the period 2014–2019.

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“…[1][2][3][4] Alcohols have been widely used in the synthesis of amines because they are easily available, and more importantly, the only byproduct of this reaction is water. [5][6][7][8][9] The N-alkylation with alcohol using the borrowing hydrogen strategy has three well-known steps: (1) The oxidation of an alcohol with a transition-metal catalyst; (2) The formation of an imine complex; (3) The imine reduction to an amine using the transition-metal catalyst. [10][11][12][13][14][15] In 1932, C. F. Winans and co-workers reported the N-alkylation of amine with alcohol by the borrowing hydrogen strategy under nickel catalysts.…”

Section: Introductionmentioning

confidence: 99%

Iron‐Catalyzed N‐Alkylation of Secondary Amines with Alcohols Using Borrowing Hydrogen Strategy

Cheng

Yang

et al. 2021

ChemistrySelect

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Iron-based catalysts have been widely used in N-alkylation of amines with alcohol using borrowing hydrogen strategy, due to low toxicity and cost. Herein, based on Saito and co-workers' experiment, we discuss a possible mechanism for N-alkylation of secondary amines with alcohol under an iron-based catalyst using DFT calculations. Contrary to N-alkylation of primary amines, only one hydrogen on alcohol benzyl group is taken by the iron-catalyst during radical transfer process. Thus, instead of forming an imine, a structure with a radical is formed.Overall, there are three parts to this mechanism: 1) hydrogen borrowing by the iron-based catalyst; 2) radical addition; 3) hydrogen reduction. There are two possible pathways of hydrogen borrowing: either by a distal oxygen or by the oxygen directly coordinating with iron. According to the computed free energy barrier, the former one is more favorable. We also found four possible pathways of radical addition. Our calculations suggest a direct dehydration step with short steps and lower energy barrier was more favorable.

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Switching the N‐Alkylation of Arylamines with Benzyl Alcohols to Imine Formation Enables the One‐Pot Synthesis of Enantioenriched α‐N‐Alkylaminophosphonates

Cited by 33 publications

References 103 publications

(Cyclopentadienone)iron Complexes: Synthesis, Mechanism and Applications in Organic Synthesis

(Cyclopentadienone)iron Complexes: Synthesis, Mechanism and Applications in Organic Synthesis

Recent Catalytic Applications of (Cyclopentadienone)iron Complexes

Iron‐Catalyzed N‐Alkylation of Secondary Amines with Alcohols Using Borrowing Hydrogen Strategy

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