Base-mediated ketenimine formation from N-sulfonylthioimidates for the synthesis of 5-amino-1-vinyl/aryl-1,2,3-triazoles

N-Sulfonylthioimidate was converted to ketenimine under basic conditions. The reaction with vinyl/aryl azides was induced to cause dipolar cycloaddition to form 5-amino-1-vinyl/aryl-1,2,3-triazoles. The advantages of this method are high efficiency, structural diversity of products favorable yields and applicability to gram-scale operations.

(E)-1-(5-Methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)-3-(naphthalen-2-yl)prop-2-en-1-one

A reaction of equimolar equivalents of 2-naphthaldehyde (1) and 1-(5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)ethan-1-one (2) in ethanolic sodium hydroxide at 20 °C for 4 h gave (E)-1-(5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)-3-(naphthalen-2-yl)prop-2-en-1-one (3) in 92% yield. Nuclear magnetic resonance spectroscopy and single-crystal X-ray diffraction were used to establish the structure of 3.

(Z)-2-(1-(5-Methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)ethylidene)-N-phenylhydrazine-1-carbothioamide

Reaction of equimolar equivalents of 1-(5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)ethan-1-one (1) and N-phenylhydrazinecarbothioamide (2) in boiling ethanol containing a catalytic amount of concentrated hydrochloric acid for 4 h gave (Z)-2-(1-(5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)ethylidene)-N-phenylhydrazine-1-carbothioamide (3) with 88% yield. The structure of 3 was established using single-crystal X-ray diffraction and magnetic resonance spectroscopy.

Synthesis and Structure Determination of 1-(4-Methoxyphenyl)-5-methyl-N’-(2-oxoindolin-3-ylidene)-1H-1,2,3-triazole-4-carbohydrazide

A reaction of equimolar equivalents of 1-(4-methoxyphenyl)-5-methyl-1H-1,2,3-triazole-4-carbohydrazide (1) and indoline-2,3-dione (2) in boiling ethanol for 4 h under acidic conditions gave 1-(4-methoxyphenyl)-5-methyl-N’-(2-oxoindolin-3-ylidene)-1H-1,2,3-triazole-4-carbohydrazide (3) in 88% yield. The structure of 3 was ascertained by NMR spectroscopy and single-crystal X-ray diffraction.

General Method of Synthesis of 5-(Het)arylamino-1,2,3-triazoles via Buchwald-Hartwig Reaction of 5-Amino- or 5-Halo-1,2,3-triazoles

An efficient access to the novel 5-(het)arylamino-1,2,3-triazole derivatives has been developed. The method is based on Buchwald-Hartwig cross-coupling reaction of 5-Amino or 5-Halo-1,2,3-triazoles with (het)aryl halides and amines, respectively. As result, it was found that palladium complex [(THP-Dipp)Pd(cinn)Cl] bearing expanded-ring N-heterocyclic carbene ligand is the most active catalyst for the process to afford the target molecules in high yields.

Three-Component Reactions of α-CF3 Carbonyls, NaN3, and Amines for the Synthesis of NH-1,2,3-Triazoles

The development of methods for the assembly of 1,2,3-triazoles is an important topic due to the broad applications of this motif in various scientific fields. In this work, we demonstrate that the three-component assembly of α-CF₃ carbonyls, NaN₃, and amines was achieved for the selective construction of a variety of 5-amino NH-1,2,3-triazoles under transition-metal-free and open-air conditions. The method provides a general and operationally simple route to functionalized biologically important molecules including carbohydrates, nucleosides, and peptides and exhibits broad substrate scopes. We further demonstrate that the NH-1,2,3-triazoles can be smoothly converted to the regiospecific N-2 alkylated 1,2,3-triazole products. Mechanistic studies based on experiments and density functional theory calculations showed that this transformation proceeds via defluorination-initiated programmed substitution/cyclization/H-transfer to give the 4,5-difunctionalized captodative NH-1,2,3-triazole product.

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.

Ceric ammonium nitrate (CAN) enabled concerted nitration/ureation of carbodiimides to synthesize o-nitroaryl ureas

A simple and facile strategy to construct o-nitroaryl urea employing carbodiimides and ceric ammonium nitrate (CAN) with high functional group compatibility via concerted nitration/ureation has been described.

Synthesis of 5-trifluoromethyl-1,2,3-triazoles via base-mediated cascade annulation of diazo compounds with trifluoroacetimidoyl chlorides

A metal-, azide- and CF₃-reagent free approach for the synthesis of 5-trifluoromethyl-1,2,3-triazoles via base-mediated cascade annulation of diazo compounds with trifluoroacetimidoyl chlorides has been developed.