Construction Of N-heterocycles Research Articles

Synthesis and Antimicrobial Activity Evaluation of Some Novel Heterocycles Derived from Chromonyl-2(3H)-furanone

6-Chloro-3-((2-oxo-5-phenylfuran-3(2 H)-ylidene)methyl)-4 H-chromen-4-one was utilised for the construction of N-heterocycles. The proclivity of this furanone towards some nitrogen nucleophiles, i.e. glycine, thiosemicarbazide, thiocarbohydrazide, phenylhydrazine and o-phenylenediamine, was studied. The structures of all products obtained were established on the basis of their analytical and spectral data. All synthesised compounds were screened for their in vitro antibacterial (two strains of bacteria; Escherichia coli and Staphylococcus aureus) and antifungal (two fungus strains; Aspergillus flavus and Candida albicans) activities. Some products exhibited promising antimicrobial activities.

Utilizing Palladium-Stabilized Zwitterions for the Construction of N-Heterocycles.

Pd catalysis provides a convenient method for the generation of zwitterionic intermediates that offer significant opportunities for the synthesis of functionalized heterocycles. The combination of electrophilic π-allyl Pd fragments and C-, N- and O-centered nucleophiles allows these intermediates to react with readily available substrates to furnish a range of high value products with control of chemo-, regio- and stereo-selectivity.

Phosphine-Catalyzed Asymmetric (3 + 2) Annulations of δ-Acetoxy Allenoates with β-Carbonyl Amides: Enantioselective Synthesis of Spirocyclic β-Keto γ-Lactams.

While the phosphine catalysis is a powerful tool for the construction of N-heterocycles, the phosphine-catalyzed annulations toward lactam motif are still extremely scarce. Here, we report the asymmetric (3 + 2) annulations of δ-acetoxy allenoates with β-carbonyl amides by using the (R)-SITCP catalyst. The δC and γC of allenoate respectively engage in annulation with the αC and N of the amide, forging a γ-lactam with good to excellent stereoselectivity.

Efficient Construction of N-heterocycles from Benzylic Ethers/Alcohols and o-Substituted Anilines without Using any Catalyst and Additive

Efficient Construction of N-heterocycles from Benzylic Ethers/Alcohols and o-Substituted Anilines without Using any Catalyst and Additive

Electrocatalytic Generation of Amidyl Radicals for N-Heterocyle Synthesis

Nitrogen-centered radicals are versatile intermediates for the construction of N-heterocycles. Unfortunately, their use in synthesis is limited due to the difficulty associated with their preparation. We have developed electrocatalytic methods for the generation of amidyl radicals from stable and easily available N-H amides1. Application of these reactive intermediates in synthesis leads to the efficient and chemoselective construction of several classes of N-heterocycles including cyclic carbamates and ureas, indoles, imidazopyridines, and benzothiazoles.

Merging rhodium-catalysed C-H activation and hydroamination in a highly selective [4+2] imine/alkyne annulation.

Catalytic C–H activation and hydroamination represent two important strategies for eco-friendly chemical synthesis with high atom efficiency and reduced waste production. Combining both C–H activation and hydroamination in a cascade process, preferably with a single catalyst, would allow rapid access to valuable nitrogen-containing molecules from readily available building blocks. Here we report a single metal catalyst-based approach for N-heterocycle construction by tandem C–H functionalization and alkene hydroamination. A simple catalyst system of cationic rhodium(I) precursor and phosphine ligand promotes redox-neutral [4+2] annulation between N–H aromatic ketimines and internal alkynes to form multi-substituted 3,4-dihydroisoquinolines (DHIQs) in high chemoselectivity over competing annulation processes, exclusive cis-diastereoselectivity, and distinct regioselectivity for alkyne addition. This study demonstrates the potential of tandem C–H activation and alkene hydrofunctionalization as a general strategy for modular and atom-efficient assembly of six-membered heterocycles with multiple chirality centres.

ChemInform Abstract: Generation of N‐Heterocycles via Tandem Reactions of N′‐(2‐Alkynylbenzylidene)hydrazides

AbstractReview: [43 refs.

ChemInform Abstract: O‐Acyl Oximes: Versatile Building Blocks for N‐Heterocycle Formation in Recent Transition Metal Catalysis

AbstractReview: [40 refs.

Annulation based on 8-aminoquinoline assisted C–H activation: an emerging tool in N-heterocycle construction

As an important emerging area of 8-aminoquinoline assisted C–H activation, the construction of heterocycles via direct C–H activation and domino reactions involving domino C–H activation/annulation has been highlighted.

Generation of N-Heterocycles via Tandem Reactions of N '-(2-Alkynylbenzylidene)hydrazides.

As a powerful synthon, N '-(2-alkynylbenzylidene)hydrazides have been utilized efficiently for the construction of N-heterocycles. Since N '-(2-alkynylbenzylidene)hydrazides can easily undergo intramolecular 6-endo cyclization promoted by silver triflate or electrophiles, the resulting isoquinolinium-2-yl amides can proceed through subsequent transformations including [3 + 2] cycloaddition, nucleophilic addition, and [3 + 3] cycloaddition. Several unexpected rearrangements via radical processes were observed in some cases, which afforded nitrogen-containing heterocycles with molecular complexity. Reactive partners including internal alkynes, arynes, ketenimines, ketenes, allenoates, and activated alkenes reacted through [3 + 2] cycloaddition and subsequent aromatization, leading to diverse H-pyrazolo[5,1-a]isoquinolines with high efficiency. Nucleophilic addition to the in situ generated isoquinolinium-2-yl amide followed by aromatization also produced H-pyrazolo[5,1-a]isoquinoline derivatives when terminal alkynes, carbonyls, enamines, and activated methylene compounds were used as nucleophiles. Isoquinoline derivatives were obtained when indoles or phosphites were employed as nucleophiles in the reactions of N '-(2-alkynylbenzylidene)hydrazides. A tandem 6-endo cyclization and [3 + 3] cycloaddition of cyclopropane-1,1-dicarboxylates with N '-(2-alkynylbenzylidene)hydrazides was observed as well. Small libraries of these compounds were constructed. Biological evaluation suggested that some compounds showed promising activities for inhibition of CDC25B, TC-PTP, HCT-116, and PTP1B.

Contemporary development in sequential Knoevenagel, Michael addition multicomponent reaction for the synthesis of 4-Aryl-5-oxo-5H-indeno[1,2-b]pyridine-3-carbonitrile

An uncatalyzed efficient synthesis of bioactive pyridine derivatives has been investigated for the first time by a three-component sequential multicomponent reaction tackled with aromatic aldehydes, malononitrile, and 1,3-indandione via Knoevenagel condensation followed by Michael addition. The difference between the domino multicomponent and sequential multicomponent reaction is emphasized by this methodology. The reaction proceeds at ambient temperature without frequently useful N-source like ammonium salt for the construction of N-heterocycles, which makes this protocol a novel synthetic route for the preparation of the indenopyridine skeleton.

ChemInform Abstract: Construction of N‐Containing Heterocycles via Oxidative Intramolecular N—H/X—H Coupling

AbstractReview: [72 refs.

Construction of N-containing heterocycles via oxidative intramolecular N-H/X-H coupling.

The preparation of N-containing heterocycles is always the core of synthetic chemistry. Recently, oxidative coupling between two R-H nucleophiles is gaining more attention due to its atom-economy and step-economy, thus there are numerous reports focusing on the N-heterocycle construction via oxidative coupling. This feature article is going to cover the methodology related to the construction of N-heterocycles through oxidative intramolecular N-H/X-H coupling.

Iron-catalyzed aerobic oxidative functionalization of sp3 C–H bonds: a versatile strategy for the construction of N-heterocycles

Iron-catalyzed aerobic oxidative functionalization of sp3 C–H bonds using a biofriendly iron catalyst in combination with O2 or air as the sole oxidant has been developed for the construction of N-heterocycles from easily available carboxylic acid derivatives and o-substituted anilines.

ChemInform Abstract: 2‐Alkynylbenzaldoxime: A Versatile Building Block for the Generation of N‐Heterocycles

AbstractReview: [33 refs.

2-Alkynylbenzaldoxime: a versatile building block for the generation of N-heterocycles.

2-Alkynylbenzaldoxime as a versatile building block has been applied widely for the construction of N-heterocycles in organic synthesis. Since it could be easily transferred to isoquinoline N-oxide via intramolecular 6-endo cyclization in the presence of metal catalysts or electrophiles, the subsequent [3 + 2] cycloaddition/nucleophilic addition and rearrangement could be expected. On the other hand, a Beckmann rearrangement could occur first since an oxime moiety is present in the molecule, which would then undergo an intramolecular cyclization to furnish nitrogen-containing heterocycles. This review reports the recent advancement in the generation of N-heterocycles starting from 2-alkynylbenzaldoximes via tandem reactions based on different reaction types.

ChemInform Abstract: Copper‐Catalyzed C—N Bond Formation/Rearrangement Sequence: Synthesis of 4H‐3,1‐Benzoxazin‐4‐ones.

Abstractas potential biologically important agents

Copper-Catalyzed C–N Bond Formation/Rearrangement Sequence: Synthesis of 4H-3,1-Benzoxazin-4-ones

A facile and efficient copper-catalyzed method for the synthesis of 4H-3,1-benzoxazin-4-one derivatives has been developed. This procedure is based on a tandem intramolecular C-N coupling/rearrangement process. This method would provide a new and useful strategy for construction of N-heterocycles.

Copper-Catalyzed Aerobic Oxidative Intramolecular C–H Amination Leading to Imidazobenzimidazole Derivatives

A highly efficient copper-catalyzed aerobic oxidative intramolecular C-H amination has been developed using substituted 2-(1H-imidazol-1-yl)-N-alkylbenzenamines as the starting materials, and the corresponding imidazobenzimidazole derivatives were obtained in excellent yields. This is an economical and practical method for the construction of N-heterocycles.

Copper‐Catalyzed One‐Pot Synthesis of Imidazo/Benzoimidazoquinazolinones by Sequential Ullmann‐Type Coupling and Intramolecular CH Amidation

A simple, practical, and highly efficient copper-catalyzed one-pot synthesis of imidazo/benzoimidazoquinazolinones has been developed. The procedure is based on a sequential copper-catalyzed Ullmann-type N-arylation and aerobic oxidative intramolecular C-H amidation. This method should provide a new and useful strategy for construction of N-heterocycles.