Aluminium(III) Chloride-Catalyzed Three-Component Condensation of Aromatic Aldehydes, Nitroalkanes and Sodium Azide for the Synthesis of 4-Aryl-NH-1,2,3-triazoles

Synthesis of Unsymmetrically Condensed Benzo- and Thienotriazologermoles

Germoles and siloles unsymmetrically condensed with heteroaromatic units are attracting much interest. In this study, compounds containing a triazologermole core unit condensed with a benzene or thiophene ring were prepared. Thienotriazologermole was subjected to bromination to obtain the bromide, which underwent transformation via the palladium-catalyzed Stille coupling reaction to form triphenylamine-substituted thienotriazolegermole, with an effective extension of conjugation. The electronic states and properties of these triazologermole derivatives are discussed on the basis of optical and electrochemical measurements and density functional theory calculations. Triphenylamine-substituted thienotriazolegermole showed clear solvatochromic properties in photoluminescence measurements, suggesting that intramolecular charge transfer occurs at the photo-excited state. This clearly indicates that the triazologermole unit is useful as an acceptor of donor-acceptor compounds. The potential application of triphenylamine-substituted thienotriazolegermole as a sensing material was also explored.

A mild protocol for efficient preparation of functional molecules containing triazole

The construction of a class of novel triazole molecules containing sulfonyl fluoride functionalities was achieved through Cu-catalyzed click chemistry in good to excellent yields. The sulfonyl fluoride moieties were cleaved completely under base conditions to produce N-unsubstituted triazoles quantitatively, which provides a strategy to combine SuFEx click chemistry with Cu-catalyzed click chemistry ingeniously.

Azide-free cyclization reaction access to 4-aryl-NH-1,2,3-triazoles: P-toluenesulfonyl hydrazide and sulfamic acid as nitrogen sources

An iodine-mediated cyclization has been developed to 4-aryl-NH-1,2,3-triazoles, with p-toluenesulfonyl hydrazide and sulfamic acid used as nitrogen sources. Sulfamic acid plays a crucial role in this reaction by both acting as a substrate and providing an acidic environment. This reaction offers a metal- and azide-free strategy to access NH-1,2,3-triazoles.

NH-1,2,3-triazoles as versatile building blocks in denitrogenative transformations

The utilization of NH-1,2,3-triazoles as easily accessible building blocks in denitrogenative ring cleavage transformations with electrophiles to provide multifunctionalized nitrogen heterocycles and N-alkenyl compounds is reviewed. Leveraging the ready availability of NH-1,2,3-triazoles, these processes provide a convenient route to a range of pharmaceutically relevant heterocyclic cores and N-alkenyl compounds. The synthetic usefulness of in situ acylated NH-1,2,3-triazoles as viable alternatives to widely explored N-sulfonyl-1,2,3-triazoles in ring cleavage processes is highlighted.

Synthesis of N-vinyl isothiocyanates and carbamates by the cleavage of NH-1,2,3-triazoles with one-carbon electrophiles

Metal-free cascade reaction of NH-1,2,3-triazoles with one-carbon electrophiles, such as thiophosgene and triphosgene, led to N-vinylated ring cleavage products. Using this approach the synthesis of N-vinylisothiocyanates from NH-triazoles and thiophosgene was achieved. A variety of multifunctional compounds, such as N-vinylcarbamates, unsymmetrical vinylureas, carbamothioates, etc. was prepared by a one-pot method from NH-triazoles, triphosgene and nucleophiles.

The Synthesis of Five-Membered N-Heterocycles by Cycloaddition of Nitroalkenes with (In)Organic Azides and Other 1,3-Dipoles

Cycloaddition reactions have emerged as rapid and powerful methods for constructing heterocycles and carbocycles. [3+2] Cyclo­additions of nitroalkenes with various 1,3-dipoles have been an interesting research area for many organic chemists. This review outlines the synthesis of N-substituted and NH-1,2,3-triazoles along with other five-membered N-heterocycles through cycloaddition reactions of nitro­alkenes.

1 Introduction

2 Synthesis of 1,2,3-Triazoles

2.1 Synthesis of NH-1,2,3-Triazoles

2.2 Synthesis of N-Substituted 1,2,3-Triazoles

3 Synthesis of Pyrrolidines and Pyrroles

4 Synthesis of Pyrazoles

5 Conclusion

One-pot synthesis of 4-substituted 2-fluoroalkyloxazoles from NH-1,2,3-triazoles and fluoroalkylated acid anhydrides

An efficient one-pot method for the synthesis of 2-fluoroalkyloxazoles from 4-substituted NH-1,2,3-triazoles, fluorinated anhydrides and triethylamine was developed.

Direct Synthesis of 4-Aryl-1,2,3-triazoles via I2-Promoted Cyclization under Metal- and Azide-Free Conditions

We herein report an iodine-mediated formal [2 + 2 + 1] cyclization of methyl ketones, p-toluenesulfonyl hydrazines, and 1-aminopyridinium iodide for preparation of 4-aryl-NH-1,2,3-triazoles under metal- and azide-free conditions. Notably, this is achieved using p-toluenesulfonyl hydrazines and 1-aminopyridinium iodide as azide surrogates, providing a novel route toNH-1,2,3-triazoles. Furthermore, this approach provides rapid and practical access to potent inhibitors of indoleamine 2,3-dioxygenase (IDO).

Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Background:

Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been used to accelerate organic transformations. With the development of environmental awareness, to obtain highly efficient scaffolds, scientists have directed their studies towards synthetic methodologies that minimize or preferably eliminate the formation of waste, avoid toxic solvents and reagents and use renewable starting materials as far as possible.

Methods:

In this connection, the organocatalytic reactions providing efficiency and selectivity for most of the transformations have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts contributing to the transformation of reactants into products with the least possible waste production, have been serving the concept of green chemistry.

Results and Conclusion:

Organocatalysts have been classified based on their binding capacity to the substrate with covalent or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol, and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.

Metal-free syntheses of N-functionalized and NH-1,2,3-triazoles: an update on recent developments

An overview of the latest developments in the metal-free synthesis of non-benzo-fused N-functionalized and NH-1,2,3-triazoles is provided in this feature article. Synthetic studies that appeared from 2016 until August 2020 are organized according to a wide-ranging classification, comprising oxidative and eliminative azide-dipolarophile cycloadditions, diazo transfer reactions and N-tosylhydrazone-mediated syntheses. The newly developed methods constitute a significant contribution to the field of 1,2,3-triazole synthesis in terms of structural variation via either the exploration of novel reactions, or the exploitation of existing methodologies.

Metal-Free Cascade [4 + 1] Cyclization Access to 4-Aryl-NH-1,2,3-triazoles from N-Tosylhydrazones and Sodium Azide

A molecular iodine-mediated coupling cyclization reaction for the synthesis of 4-aryl-NH-1,2,3-triazoles has been developed from N-tosylhydrazones and sodium azide. This metal-free cascade [4 + 1] cyclization reaction could rapidly synthesize valuable compounds via a sequential C-N and N-N bond formation. Mechanistic studies demostrate that the nitrogen atoms of the 1,2,3-triazoles are not entirely from sodium azide.

In-Water Synthesis of 5-Thiolated 1,2,3-Triazoles from β-Thioenaminones by Diazo Transfer Reaction

The synthesis of 1,2,3-triazoles with a sulfur-based side chain has been accessed with the metal-free annulation reactions of readily available β-thiolated enaminones and tosyl hydrazine. By these reactions with water as the only medium, a broad array of 5-thiolated 1,2,3-triazoles have been synthesized with generally good to excellent yields. Except using TMEDA (N,N,N',N'-tetramethylethylenediamine) as the only base promoter, not any other catalyst or additive is required, thus providing an efficient and environmentally benign method for useful 1,2,3-triazole synthesis.

Catalyst-free synthesis of 4-acyl-NH-1,2,3-triazoles by water-mediated cycloaddition reactions of enaminones and tosyl azide

The synthesis of 4-acyl-NH-1,2,3-triazoles has been accomplished with high efficiency through the cycloaddition reactions between N,N-dimethylenaminones and tosyl azide. This method is featured with extraordinary sustainability by employing water as the sole medium, free of any catalyst or additive, authentically mild conditions (40 °C stirring) as well as practical scalability.

Copper-Catalyzed Cross-Dehydrogenative N2-Coupling of NH-1,2,3-Triazoles with N,N -Dialkylamides: N-Amidoalkylation of NH-1,2,3-Triazoles

An efficient copper-catalyzed C-N bond formation by N-H/C-H cross-dehydrogenative coupling (CDC) between NH-1,2,3-triazoles and N,N-dialkylamides has been developed. The method provided N-amidoalkylated 1,2,3-triazoles with moderate to high yields, and the reactions showed high N²-selectivities when 4,5-disubstituted NH-1,2,3-triazoles served as the substrates.

Base-Promoted Synthesis of N-Substituted 1,2,3-Triazoles via Enaminone-Azide Cycloaddition Involving Regitz Diazo Transfer

The domino reactions between NH-based secondary enaminones and tosyl azide have been developed for the synthesis of various N-substituted 1,2,3-triazoles by employing t-BuONa as the base promoter. Through a key Regitz diazo-transfer process with tosyl azide, the reactions proceed efficiently at room temperature with good substrate tolerance.