Copper-Catalyzed Direct Amidation of Heterocycles with N-Fluorobenzenesulfonimide

Copper-Catalyzed Regioselective Imidation of 2-Pyridones

We demonstrate a ligand- and glovebox-free regioselective direct C(3)-H imidation of 2-pyridones and also benzylic-type imidation of 2-pyridones bearing a methyl substituent employing Cu(OAc)2·H2O as the catalyst and N-fluorobenzenesulfonimide (NFSI) as an imidating reagent. A broad range of imidated 2-pyridone derivatives is made up to excellent yields. The present strategy operates well on a gram scale, and the ensuing product can be readily subjected to mono- and bis-desulfonylation reactions.

Copper-Catalyzed Intermolecular Cross-dehydrogenative C-N Coupling at Room Temperature via Remote Activating Group Enabled Radical Relay Strategy

Employing N-fluorobenzenesulfonimide (NFSI) as a nitrogen-centered radical (NCR) precursor, an intermolecular C(sp²)-N coupling on heteroarenes or substituted benzenes with remote activated aniline derivatives via copper catalyzed N-N radical relay strategy at room temperature is developed. Good to excellent yields are acquired, and no ligand or additive is required. Reaction scope investigation and preliminary mechanistic studies demonstrate that the remote activating strategy and delicate control on the reactivities of active NCR species are essential to guarantee satisfactory chemo- and site-selectivity.

Conversion of a AuI Fluorido Complex into an N-Fluoroamido Derivative: N-F versus Au-N Reactivity

The Au^I complex [Au{N(F)SO₂ Ph}(SPhos)] (SPhos=dicyclohexyl(2',6'-dimethoxy[1,1'-biphenyl]-2-yl)phosphane) (2) bearing a fluoroamido ligand has been synthesized by reaction of the fluorido complex [Au(F)(SPhos)] (1) with NFSI (NFSI=N-fluorobenzenesulfonimide). A reaction with CO resulted in an unprecedented insertion into the N-F bond at 2. With the carbene precursor N₂ CH(CO₂ Et) N-F bond cleavage gave the Au-F bond insertion product [Au{CHF(CO₂ C₂ H₅ )}(SPhos)] (7). The presence of CNtBu led to Au-N cleavage at 2 and concomitant amide formation to give the cationic complex [Au(CNtBu)(SPhos)][N(F)SO₂ Ph)] (5), which reacted further to give FtBu as well as the cyanido complex [Au(CN)(SPhos)] (6). These results led to the development of a process for the amination of electrophilic organic substrates by transfer of the fluoroamido group NF(SO₂ Ph)^- .

Cu-α-diimine Compounds Encapsulated in Porous Materials as Catalysts for Electrophilic Amination of Aromatic C-H Bonds

Electrophilic amination has emerged as a more environmentally benign approach to construct arene C-N bonds. However, heterogeneous catalysts remain largely unexplored in this area, even though their use could facilitate product purification and catalyst recovery. Here we investigate strategies to heterogenize a Cu(2,2'-bipyridine) catalyst for the amination of arenes lacking a directing group with hydroxylamine-O-sulfonic acid (HOSA). Besides immobilization of Cu on a metal-organic framework (MOF) or covalent organic framework (COF) with embedded 2,2'-bipyridines, a ship-in-a-bottle approach was followed in which the Cu complex is encapsulated in the pores of a zeolite. Recyclability and hot centrifugation tests show that zeolite Beta-entrapped Cu^II(2,2'-bipyridine) is superior in terms of stability. With N-methylmorpholine as a weakly coordinating, weak base, simple arenes, such as mesitylene, could be aminated with yields up to 59%, corresponding to a catalyst TON of 24. The zeolite could be used in three consecutive runs without a decrease in activity. Characterization of the catalyst by EPR and XAS showed that the active catalytic complex consisted of a site-isolated Cu^II species with one 2,2'-bipyridine ligand.

Synthesis of 2-Aminofurans and 2-Aminothiophenes through Elemental Sulfur-Promoted Switchable Redox Condensation Reaction of Enaminones with Methylene Nitriles

Herein, we report an elemental sulfur-promoted switchable redox condensation reaction that can selectively prepare 2-aminofurans and 2-aminothiophenes from the corresponding enaminones and methylene nitriles, respectively. Mechanistic studies demonstrated that the enaminones, as dual nucleophiles, reacted with nitrile acetate to produce 2-aminofurans via 3,5-annulation under promotion by elemental sulfur. These reactions used readily available starting materials, transition metal-free, eco-friendly procedures, gram-scale syntheses, and wide functional group tolerance. The methodology may be useful for the construction of 2-aminofuran and 2-aminothiophene derivatives with potential biological activity.

An N-Fluorinated Imide for Practical Catalytic Imidations

Catalytic imidation using NFSI as the nitrogen source has become an emerging tool for oxidative carbon-nitrogen bond formation. However, the less than ideal benzenesulfonimide moiety is incorporated into products, severely detracting its synthetic value. As a solution to this challenge, we report herein the development of a novel N-fluorinated imide, N-fluoro-N-(fluorosulfonyl)carbamate (NFC), by which the attached imide moiety acts as a modular synthetic handle for one-step derivatization to amines, sulfonamides, and sulfamides. Furthermore, this study revealed the superior reactivity of NFC as showcased in a copper-catalyzed imidation of benzene derivatives and imidocyanation of aliphatic alkenes, overcoming the limitation of NFSI-mediated reactions.

C–N coupling reactions with arenes through C–H activation: the state-of-the-art versus the principles of green chemistry

Herein, we discuss the state-of-the-art in arene C–N coupling through C–H activation and to what extent it complies with the principles of green chemistry, with a focus on heterogeneously catalysed systems.

Toolbox for Distal C-H Bond Functionalizations in Organic Molecules

Transition metal catalyzed C-H activation has developed a contemporary approach to the omnipresent area of retrosynthetic disconnection. Scientific researchers have been tempted to take the help of this methodology to plan their synthetic discourses. This paradigm shift has helped in the development of industrial units as well, making the synthesis of natural products and pharmaceutical drugs step-economical. In the vast zone of C-H bond activation, the functionalization of proximal C-H bonds has gained utmost popularity. Unlike the activation of proximal C-H bonds, the distal C-H functionalization is more strenuous and requires distinctly specialized techniques. In this review, we have compiled various methods adopted to functionalize distal C-H bonds, mechanistic insights within each of these procedures, and the scope of the methodology. With this review, we give a complete overview of the expeditious progress the distal C-H activation has made in the field of synthetic organic chemistry while also highlighting its pitfalls, thus leaving the field open for further synthetic modifications.

Direct Synthesis of CF2H-Substituted 2-Amidofurans via Copper-Catalyzed Addition of Difluorinated Diazoacetone to Ynamides

The significance of molecules containing difluoromethyl groups is driven by their potential applications in pharmaceutical and agrochemical science. Methods for the incorporation of lightly fluorinated groups such as CF₂H have been less well developed. Here we report the use of difluorinated diazoacetone as a practical reagent for the direct synthesis of CF₂H-substituted 2-amidofurans through addition to ynamides. These newly designed difluorinated amidofurans were elaborated to create new nitrogen-containing frameworks that would be challenging to obtain otherwise.

Short and Modular Synthesis of Substituted 2-Aminopyrroles

We herein describe a simple and metal-free domino methodology to synthesize 2-aminopyrroles from alkynyl vinyl hydrazides. The domino reaction involves a novel propargylic 3,4-diaza-Cope rearrangement and a tandem isomerization/5-exo-dig N-cyclization reaction. By using this approach, a number of 2-aminopyrroles with diverse substituents have been prepared.

Ligand-free copper-catalyzed C(sp3)-H imidation of aromatic and aliphatic methyl sulfides with N-fluorobenzenesulfonimide

A novel and efficient process has been developed for copper-catalyzed C(sp3)-H direct imidation of methyl sulfides with N-fluorobenzenesulfonimide(NFSI). Without using any ligands, various methyl sulfides including aromatic and aliphatic methyl sulfides, can be transformed to the corresponding N-((phenylthio)methyl)-benzenesulfonamide derivatives in good to excellent yields.

Recent Advances in Copper-Catalyzed Radical C–H Bond Activation Using N–F Reagents

This Short Review is aimed at giving an update in the area of copper-catalyzed C–H functionalization involving nitrogen-centered radicals generated from substrates containing N–F bonds. These processes include intermolecular Csp3–H bond functionalization, remote Csp3–H bond functionalization via intramolecular hydrogen atom transfer (HAT), and Csp2–H bond functionalization, which might be of potential use in industrial applications in the future.

1 Introduction

2 Intermolecular Csp3–H Functionalization

3 Remote Csp3–H Functionalization

4 Csp2–H Functionalization

5 Conclusion

Synergetic copper/TEMPO-catalysed benzylic C–H imidation with N-fluorobenzenesulfonimide at room temperature and tandem conversions with alcohols or arenes

A remote carbamate-directed benzylic C–H imidation with NFSI at room temperature through synergetic CuCl-TEMPO catalysis and tandem alkoxylation or arylation with alcohols or arenes are described.

Copper-catalysed radical reactions of alkenes, alkynes and cyclopropanes with N-F reagents

The mild generation of nitrogen-centred radicals from N-F reagents has become a convenient synthetic tool. This methodology provides access to the aminative difunctionalisation of alkenes and alkynes and the radical ring-opening of cyclopropanes, among other similar transformations. This review article aims to provide an overview of recent developments of such processes involving radical reactions and N-F reagents using copper-based catalysts.

Exploring the behavior of the NFSI reagent as a nitrogen source

The diverse biological activities of nitrogen-containing compounds make the construction of the C-N bond of great importance. As N-fluorobenzenesulfonimide, one of the most abundant chemical feedstock, has a dual behaviour, i.e. as an electrophilic fluorination and amidation source, it attracts the attention of synthetic chemists for exploitation. This review comprehensively summarizes the significant progress of the efficient and mild amidation reactions, with an emphasis on approaches for the generation of nitrogen-centered intermediates, related mechanisms and new synthetic chemistry methods that offer opportunities to overcome obstacles in pharmaceutical applications. In this perspective, we discuss the developments in the amidation reaction using NFSI in the past decade. We discuss the recent progress, challenges and future outcomes in the area of amidation chemistry using commercially available NFSI.

Copper-Catalyzed 1,2-Aminocyanation of Unactivated Alkenes via Cyano Migration

A copper-catalyzed aminocyanation of alkenes has been achieved through distal cyano migration using O-benzoylhydroxylamines and N-fluorobenzenesulfonimides. This method offers a rapid approach to generate diverse β-amino and β-sulfonimido nitriles. These reactions feature mild conditions, tolerance of sensitive functional groups, and excellent regioselectivity. Mechanistic studies suggest that these transformations are initiated by a copper-catalyzed amination step followed by a cyano migration step.

C-H Imidation and Dual C-H Bond Aminobromination of Five-Membered Heterocycles

Here, we report a practical C-H imidation of five-membered heterocycles under metal-free conditions. We also report the first dual C-H bond aminobromination of thiophenes, with benzotriazole, saccharin, 1,2,4-triazole, benzimidazole, pyrazole, 4-bromopyrazole, 5-methyltetrazole, and dibenzenesulfonimides as effective amine sources. Mechanistic studies support the radical pathway of the imidation and aminobromination reactions.

N-Fluorobenzenesulfonimide: a useful and versatile reagent for the direct fluorination and amination of (hetero)aromatic C–H bonds

This review updates recent advances and developments in the direct fluorination and amination of (hetero)aromatic C–H bonds utilizing N-fluorobenzenesulfonimide, classified according to the type of catalyst.

This review updates recent advances and developments in the direct fluorination and amination of (hetero)aromatic C–H bonds utilizing N-fluorobenzenesulfonimide, classified according to the type of catalyst.

Nickel-promoted C(2)–H amidation of quinoline N-oxides with N-fluorobenzenesulfonimide

The first example of nickel-promoted C–H amidation of quinoline N-oxides with NFSI.

Metal-free C–H amination of arene with N-fluorobenzenesulfonimide catalysed by nitroxyl radicals at room temperature

The first C–H amination of arene with NFSI via organocatalysis is disclosed, which can be achieved at room temperature with a broad substrate scope.

3d Transition Metals for C-H Activation

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

(Diacetoxy)iodobenzene-Mediated Regioselective Imidation of Imidazoheterocycles with N-Fluorobenzenesulfonimide

Metal-free (diacetoxy)iodobenzene-mediated regioselective imidation of imidazoheterocycles using commercially available N-fluorobenzenesulfonimide as an imidating reagent has been developed. This protocol exhibits broad substrate scope with good to excellent yields of the imidated imidazopyridines under mild conditions in short reaction times. The present protocol also represents an efficient way to access the imidated derivatives of imidazo[2,1-b]thiazole, benzo[d]imidazo-[2,1-b]thiazole, indoles, and indolizines. A radical mechanistic pathway has been proposed for the present protocol.

C-H Imidation of 7-Deazapurines

We developed and presented here a ferrocene-catalyzed C-H imidation of 7-deazapurines (pyrrolo[2,3-d]pyrimidines) with N-imidyl peroxyesters. The reactions occur regioselectively at position 8 in 7-deazapurines, leading to a series of 8-succinimido-, phtalimido-, or naphthalimido-7-deazapurine derivatives. Attempted hydrazinolysis of resulting 8-imidyl-7-deazapurines led to corresponding 8-amino-7-deazapurine, which was very unstable and quickly decomposed.

NFSI-participated intermolecular aminoazidation of alkene through iron catalysis

An iron-catalysed intermolecular vicinal aminoazidation of alkene with NFSI is reported, with broader alkene scope comparing to previously reported aminoazidation.

Preparation of 2-Amino-5-homoallylfurans via Palladium-Catalyzed Tandem Cycloisomerization/Heck-Type Coupling of Homoallenyl Amides with Allyltrialkylsilanes

The direct access to 2-amino-5-homoallylfurans has been realized by a palladium-catalyzed tandem cycloisomerization/Heck-type coupling between homoallenyl amides and allyltrialkylsilanes, using a novel DDQ/MnO₂ combination as the efficient oxidant. The reaction exclusively affords γ-allylation products in good to excellent yields with broad substrate scope under exceptionally mild reaction conditions. It represents one of the rare examples of the Pd-catalyzed intermolecular Heck-type coupling of allytrialkylsilanes terminated by β-silyl elimination, thus complementing traditional allylation methods because of the excellent γ-selectivity.

Aromatic C-H amination: a radical approach for adding new functions into biology- and materials-oriented aromatics

C-H amination is the most powerful method to directly add nitrogen functionalities into a variety of arenes including biology- and materials-oriented molecules. Recent developments in aromatic C-H amination chemistry have enabled the conversion of unactivated arenes into a range of arylamine derivatives without using directing groups or excess amounts of arenes. The key for such successful transformations is the catalytic generation of nitrogen or arene radical intermediates. In this perspective, we discuss recent developments in the radical C-H amination of aromatic molecules. We believe the resulting arylamines, which are hitherto difficult to access, will exhibit unexplored functions for biological and materials application.

Copper-catalyzed regioselective 1,2-thioamidation of alkenes

An efficient method for regioselective 1,2-thioamidation of terminal alkenes, catalyzed by copper in the presence of NFSI and thiols, has been disclosed.

Copper(i) and N-fluorobenzenesulfonimide-mediated direct regioselective halogenation of 8-amidoquinolines on the C5 position

Direct regioselective halogenation of 8-amidoquinolines on the C5 position in the presence of NFSI and CuX under mild conditions.

Visible light-induced C3-sulfonamidation of imidazopyridines with sulfamides

A visible light-induced regioselective sulfonamidation of imidazo[1,2-a]pyridines was developed using sulfamides as the nitrogen sources and aqueous NaClO solution as the oxidant under mild conditions.

Synthesis of N,N-disubstituted 2-aminothiophenes by the cyclization of gem-difluoroalkenes with β-keto thioamides

A novel and effective method for the construction of highly functionalized aminothiophenes via the cyclization of gem-difluoroalkenes with β-keto tertiary thioamides is described.

C–H imidation: a distinct perspective of C–N bond formation

The direct imidation strategy proficiently constructs C–N bonds and creates the useful amine functional group in the molecular template.