Iron-Catalyzed Acceptorless Dehydrogenative Coupling of Alcohols With Aromatic Diamines: Selective Synthesis of 1,2-Disubstituted Benzimidazoles

Putta, Ramachandra Reddy; Chun, Sang-Hyun; Lee, Seok Beom; Oh, Dong Kyu; Hong, Suckchang

doi:10.3389/fchem.2020.00429

Cited by 32 publications

(15 citation statements)

References 46 publications

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“…The Knölker catalyst is known to promote efficiently hydrogen transfer and hydrogen borrowing transformation via outer-sphere hydride transfer/protonation-deprotonation fashion. − The catalytic reduction of nitroarenes to anilines can be evolved along two pathways (Scheme ). Thus, starting from nitroarenes, the reduced iron species [FeH 2 ] underwent the reduction of the nitro moiety, leading to an arylnitroso 9 regenerating the Knölker catalyst [Fe] and aldehyde.…”

Section: Resultsmentioning

confidence: 99%

“…More particularly, iron, being the most abundant and inexpensive transition metal on Earth, the last two decades have seen an impressive growth of its use in homogeneous catalysis . Thus, numerous examples of iron-catalyzed reductive coupling reactions were reported including amination reactions which can be efficiently promoted via a hydrogen borrowing pathway at rather high temperatures starting from alcohols, notably using Knölker-type catalysts. − …”

Section: Introductionmentioning

confidence: 99%

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Iron-Catalyzed Hydrogen Transfer Reduction of Nitroarenes with Alcohols: Synthesis of Imines and Aza Heterocycles

Darcel

2020

J. Org. Chem.

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A straightforward and selective reduction of nitroarenes with various alcohols was efficiently developed using an iron catalyst via a hydrogen transfer methodology. This protocol led specifically to imines in 30−91% yields, with a good functional group tolerance. Noticeably, starting from o-nitroaniline derivatives, in the presence of alcohols, benzimidazoles can be obtained in 64− 72% yields when the reaction was performed with an additional oxidant, DDQ, and quinoxalines were prepared from 1,2-diols in 28−96% yields. This methodology, unprecedented at iron for imines, also provides a sustainable alternative for the preparation of quinoxalines and benzimidazoles.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Iron-Catalyzed Hydrogen Transfer Reduction of Nitroarenes with Alcohols: Synthesis of Imines and Aza Heterocycles

Darcel

2020

J. Org. Chem.

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Section: Telmisartanmentioning

confidence: 99%

“…A similar dehydrogenative approach to obtain benzimidazole was adapted b and coworkers. They tested, for the first time, the ability of a Knölker-type catalys bonyl (η 4 -cyclopentadione) iron complexes, to promote oxidative coupling betwe stituted aryl diamines and alcohols to produce N-alkylated benzimidazoles (Sch [86]. This appealing methodology permits achieving 2-substituted benzimidazoles in outstanding yields (e.g., 81 a-d), avoiding the use of additives or an exogenous base.…”

Section: Metal-catalyzed Annulation In Benzimidazole Synthesismentioning

confidence: 99%

“…A similar dehydrogenative approach to obtain benzimidazole was adapted by Hong and coworkers. They tested, for the first time, the ability of a Knölker-type catalyst, tricarbonyl (η 4 -cyclopentadione) iron complexes, to promote oxidative coupling between substituted aryl diamines and alcohols to produce N-alkylated benzimidazoles (Scheme 34) [86]. The first reported case of iron-catalyzed dehydrogenative coupling ing substituted benzimidazoles in great yields (e.g., 82 a-d) in relatively The regioselectivity of the reaction is modifiable as a function of the el the group tethered to alcohols (electron-rich heteroaromatic substituent gioselectivity).…”

Section: Metal-catalyzed Annulation In Benzimidazole Synthesismentioning

confidence: 99%

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Metal-Promoted Heterocyclization: A Heterosynthetic Approach to Face a Pandemic Crisis

2021

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The outbreak of SARS-CoV-2 has drastically changed our everyday life and the life of scientists from all over the world. In the last year, the scientific community has faced this worldwide threat using any tool available in order to find an effective response. The recent formulation, production, and ongoing administration of vaccines represent a starting point in the battle against SARS-CoV-2, but they cannot be the only aid available. In this regard, the use of drugs capable to mitigate and fight the virus is a crucial aspect of the pharmacological strategy. Among the plethora of approved drugs, a consistent element is a heterocyclic framework inside its skeleton. Heterocycles have played a pivotal role for decades in the pharmaceutical industry due to their high bioactivity derived from anticancer, antiviral, and anti-inflammatory capabilities. In this context, the development of new performing and sustainable synthetic strategies to obtain heterocyclic molecules has become a key focus of scientists. In this review, we present the recent trends in metal-promoted heterocyclization, and we focus our attention on the construction of heterocycles associated with the skeleton of drugs targeting SARS-CoV-2 coronavirus.

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Iron Half‐Sandwich Complexes for Catalysis

Korb¹

2022

Encyclopedia of Inorganic and Bioinorganic Chemistry

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As the most abundant transition metal, iron is well‐known for its rich complex chemistry and variety of oxidation states. In recent years, iron salts such as Fe II/III halides and acetylacetonate complexes have been employed as (pre‐)catalysts in a variety of chemical transformations, including those mediated by Lewis acid activation of functional groups, redox‐catalysis, and cross‐coupling reactions. However, the absence of stable ligand spheres or ligand lability limits the application of these “naked” salts and complexes, with the properties of the catalytically active species being predominantly determined by donor functionalities of solvent, substrate, and additives in the reaction. Improvements in catalyst design arise from introduction of multidentate pyridine‐ and other N‐based ligand designs, many of which, however, still require high catalyst loadings. The iron half‐sandwich motif, offers a robustly bonded cyclic ligand, most commonly η 5 ‐cyclopentadienyl (Cp − ), which occupies half of the available coordination sites. Additional ligands complete the complex design and allow tuning of the electronic, steric, and geometric properties of the active species. This article provides an overview of catalytic processes in which iron half‐sandwich complexes play a key role. Rather than the synthesis of the iron complexes or the substrate scope, focus is put on the properties of the active species and mechanistic aspects, to provide an overview of the rich chemistry that the half‐sandwich motif offers.

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Iron-Catalyzed Acceptorless Dehydrogenative Coupling of Alcohols With Aromatic Diamines: Selective Synthesis of 1,2-Disubstituted Benzimidazoles

Cited by 32 publications

References 46 publications

Iron-Catalyzed Hydrogen Transfer Reduction of Nitroarenes with Alcohols: Synthesis of Imines and Aza Heterocycles

Iron-Catalyzed Hydrogen Transfer Reduction of Nitroarenes with Alcohols: Synthesis of Imines and Aza Heterocycles

Metal-Promoted Heterocyclization: A Heterosynthetic Approach to Face a Pandemic Crisis

Iron Half‐Sandwich Complexes for Catalysis

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