An Annulative Electrophilic Amination Approach to 3-Aminobenzoheteroles

Copper-Catalyzed Diamination of Alkenes using o-Benzoylhydroxylamines to Access the Four Azaindoline Families

A mild and efficient method for the copper-catalyzed diamination of alkenes is described. In this reaction, o-benzoylhydroxylamine serves as an electrophilic nitrogen source for the regioselective formation of C-N bonds. This transformation provides a novel strategy for synthesizing all four isomeric 2,3-disubstituted azaindoline families and offers a wide substrate scope.

Copper-Catalyzed Tandem Cyclization/Chalcogenation with Elemental S8/Se: Concise Synthesis of 3-(β-Hydroxychalcogen)benzofurans

A novel copper-catalyzed cyclization/chalcogenation of o-alkynylphenols with epoxides and elemental S8/Se was developed for the synthesis of a 3-chalcogen-benzofuran architecture in a domino process with no intermediate isolation or purification. Various sensitive functional groups were compatible at room temperature and furnished chalcogenation derivatives in moderate to good yields.

Chemo- and regio-selective amidation of indoles with isocyanates using borane Lewis acids

A metal-free synthetic route using boranes has been developed for the amidation of indoles. A detailed mechanistic study was carried out to understand the reaction mechanism.

Copper-Catalyzed Aerobic Oxidative Cyclization of 2-Alkynylanilines with Nitrosoarenes: Synthesis of Organic Solid Mechanoluminescence Compounds of 4-Oxo-4H-cinnolin-2-ium-1-ide

An efficient Cu(I)/DMAP/air system for the one-pot synthesis of 4-oxo-4H-cinnolin-2-ium-1-ides, which are often difficult to prepare by traditional routes from substituted 2-alkynylanilines and nitrosoarenes, was developed. These 4-oxo-4H-cinnolin-2-ium-1-ides have practical applications as mechanoluminescent materials. Preliminary mechanistic experiments were performed, and a plausible mechanism for this tandem process is proposed. The use of an inexpensive copper catalyst and molecular oxygen as the oxygen source and the oxidant make this an attractive green protocol with potential synthetic applications.

Copper-Catalyzed Preparation of Benzo[3,4]indolo[1,2-b]isoquinoline-8-ones and Photoluminescence Exploration

A facile synthesis of benzo[3,4]indolo[1,2-b]isoquinolin-8-ones is described. Under copper catalysis, the reaction proceeds with a high efficiency and a broad reaction scope. A deuteration experiment shows that the KIE value is 2.85. From the results on mechanism studies, copper-catalyzed C-H activation, intramolecular cis-addition of alkynes, and reductive elimination are involved. Moreover, this skeleton is indeed a new fluorophore, and its photophysical properties are also investigated.

Benzofuran: A Key Heterocycle - Ring Closure And Beyond

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The benzofuranyl motif present in compounds exhibits various medicinal properties and non-drug applications. These derivatives are naturally occurring compounds or synthetic materials, which cover a broad spectrum of pharmacological activities like anti-inflammatory, anti-diabetic, anti- depressant, anti-HIV, anti-microbial, anti-proliferative, anti-convulsant, cytotoxic, analgesic, etc. Few of the commercially interesting compounds from this class are, ailanthoidol (anti-inflammatory), amiodarone, dronedarone, celivarone (anti-arrhythmic), bufuralol (muscular airways relaxant), morphine, 5-(2-aminopropyl)benzofuran; 5-APB, 6-(2-aminopropyl)benzofuran; 6-APB (CNS), rifampicin (antibiotic), etc., whereas, some of the non-drug applications are in perfumery industry (bergapten) and as tannin activators in sunscreen preparations (psoralen, 8-methoxypsoralen, and angelicin). Considering these interesting biological activities and commercial utilities, a review on the synthetic aspects of this privileged scaffold was attempted. For the benefit of natural product-based drug discovery, available sources of these derivatives, extraction process and reported biological activities have also been outlined in this review.

Recent advances in the synthesis of indoles from alkynes and nitrogen sources

This review highlights ten years of success in the synthesis of indoles using alkynes and nitrogen sources as substrates.

Direct and Selective 3-Amidation of Indoles Using Electrophilic N-[(Benzenesulfonyl)oxy]amides

Selective C-H amidation of 1H-indoles at the C3 position is reported as a direct entry to biologically important 3-aminoindoles. This transformation is achieved using novel N-[(benzenesulfonyl)oxy]amides as electrophilic nitrogen agents in the presence of ZnCl₂. Interestingly, analogous reactions in the absence of ZnCl₂ resulted in the formation of indole aminal products.

Synthesis of 2,3-dihydro-1H-pyrroles by intramolecular cyclization of N-(3-butynyl)-sulfonamides

Hydroamination of 3-butynamine derivatives to give non-aromatic 2,3-dihydropyrroles was achieved by using PdCl₂ or AuCl as the catalyst.

Transition-Metal-Catalyzed Electrophilic Amination: Application of O-Benzoylhydroxylamines in the Construction of the C-N Bond

Transition-metal-catalyzed electrophilic amination has been developed into a powerful tool for C-N bond construction. So far, O-benzoylhydroxylamines are the most widely used electrophilic aminating reagents. Herein, we summarize the recent advances of O-benzoylhydroxylamines involved in electrophilic amination catalyzed by transition metals. Several pioneering studies and some of the relevant mechanisms are discussed in this review.

A facile one-pot synthesis of 2,3-diarylated benzo[b]furans via relay NHC and palladium catalysis

An efficient one-pot synthesis of 2,3-diarylated benzo[b]furans was realized through the relay catalysis of N-Heterocyclic Carbene (NHC) and palladium from substituted 2'-bromodiphenylbromomethanes and aryl aldehydes. The easy availability of the starting materials, good compatibility of catalysts, convergent assembly and concomitant modification of the target scaffold, and potential utilization value of the products make this strategy attractive in organic synthesis.

Palladium-catalyzed alkyne polyannulation of diphenols and unactivated internal diynes: a new synthetic route to functional heterocyclic polymers

A new polymerization route for the preparation of functional heterocyclic polymers was developed from diphenol derivatives and unactivated internal diynes.

Copper-catalyzed oxyamination of electron-deficient alkenes with N-acyloxyamines

An intermolecular version of copper-catalyzed oxyamination of electron-deficient alkenes by making use of N-acyloxyamines as both amino and oxygen donors was developed.

Copper-Catalyzed Electrophilic Amination of Heteroarenes via C-H Alumination

A highly efficient Cu-catalyzed electrophilic amination reaction of readily available heteroarenes with O-benzoyl hydroxylamines via a one-pot C-H alumination is reported. The reactions were catalyzed using 1 mol % of CuCl to afford various heteroaryl amines in good to excellent yields. The direct C-H lithiation/transalumination of heteroarenes and catalytic amination sequence can be performed in a single vessel on gram scales.

Diversified Synthesis of Furans by Coupling between Enols/1,3-Dicarbonyl Compounds and Nitroolefins: Direct Access to Dioxa[5]helicenes

A versatile method for the diversified synthesis of furans and arenofurans has been developed that proceeds through K2CO3-promoted cyclization between enols/1,3-dicarbonyl compounds and nitroolefins at reflux in EtOH. This facile method has been successfully employed in the synthesis of benzotrifuran derivatives, which are useful hole-transporting materials. This procedure also provides direct access to dioxa[5]helicenes. This reaction offers a broad substrate scope, uses an inexpensive base and environmentally benign solvent, and is operationally simple.

Direct assembly of 3,4-difunctionalized benzofurans and polycyclic benzofurans by phenol dearomatization and palladium-catalyzed domino reaction

A method to directly convert 2-alkynylphenols to 3,4-difunctionalized benzofurans and polycyclic benzofurans was developed. This protocol involves a hypervalent-iodine-mediated oxidative dearomatization to break the aromaticity of 2-alkynylphenols, and a palladium-catalyzed domino reaction to install two functional groups at the C3 and the C4 positions and restore the aromaticity of benzofurans.

Copper-catalyzed enantioselective formal hydroamination of oxa- and azabicyclic alkenes with hydrosilanes and hydroxylamines

A CuCl/(R,R)-Ph-BPE-catalyzed enantioselective formal hydroamination of oxa- and azabicyclic alkenes with polymethylhydrosiloxane (PMHS) and O-benzoylhydroxylamines has been developed. The efficient and stereoselective net addition of hydrogen and nitrogen atoms provides the corresponding optically active oxa- and azanorbornenyl- and -norbornanylamines in good yields and good enantiomeric ratios.