From boom to bloom: synthesis of diazidodifluoromethane, its stability and applicability in the 'click' reaction

Diazidodifluoromethane was prepared from dibromodifluoromethane, sodium azide and an alkanethiolate initiator. It represents the first example of a diazidomethane that is stable enough to be used in synthesis. The stability of (poly)azidomethanes was explored with ab initio calculations. Copper(I)-catalysed azide-alkyne cycloaddition of the title azide with alkynes afforded difluoromethylene-containing bis(1,2,3-triazoles)amenable to Rh(II)-catalysed transannulation with nitriles to difluoromethylene bis(imidazoles).

Transformation of 5-acylated N-fluoroalkyl-1,2,3-triazoles to trifluoromethylated ring-fused isoquinolines, 1,3-oxazines, and 1,3-oxazin-6-ones via ketenimines

A one-pot multistep methodology leading to trifluoromethylated cyclopenta[c]isoquinolines, indeno[1,2-c]isoquinolines, 6,6-difluoro-1,3-oxazines, or 1,3-oxazin-6-ones, based on the reaction of 5-acylated N-pentafluoroethyl-substituted 1,2,3-triazoles is presented. A thermal ring opening of the starting triazoles, followed by a 1,2-acyl shift formed reactive ketenimines which cyclized after a rearrangement in a substrate-specific manner to provide new trifluoromethylated heterocyclic products.

Lewis acid-mediated transformations of 5-acyl-N-fluoroalkyl-1,2,3-triazoles to cyclopentenones, indenones, or oxazoles

We present a transition metal-free approach to 2-N-substituted indenones, cyclopentenones, and 4-carbonyl oxazoles, based on the reaction of 5-acylated N-fluoroalkyl substituted 1,2,3-triazoles (prepared by a three-component click reaction of copper acetylides, fluoroalkyl azides, and acyl chlorides) with Lewis acids aluminium trichloride or boron trifluoride etherate, proceeding via the generation and cyclization of vinyl cations.

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 and Cycloaddition Reactions of 1-Azido-1,1,2,2-tetrafluoroethane

A new fluorinated azidoethane─1-azido-1,1,2,2-tetrafluoroethane─was prepared in quantitative yield by the addition of an azide anion to tetrafluoroethylene in a protic medium. The title azide was shown to be thermally stable and insensitive to impact. Copper(I)-catalyzed [3 + 2] cycloaddition with alkynes afforded 4-substituted N-tetrafluoroethyl-1,2,3-triazoles which underwent rhodium(II)-catalyzed transannulation with nitriles to novel N-tetrafluoroethylimidazoles or the reaction with triflic acid to enamido triflates. [3 + 2] Cycloaddition of the title azide with primary amines afforded novel 5-difluoromethyl tetrazoles.

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.

Lewis-Acid-Mediated Intramolecular Cyclization of 4-Aryl-5-allyl-1,2,3-triazoles to Substituted Cyclopentene Derivatives

4-Aryl-5-allyl-N-fluoroalkyl-1,2,3-triazoles available by a three-component reaction of fluoroalkyl azides, copper acetylides, and allyl halides underwent aluminum halide-mediated transformation to N-(4-halo-2-aryl-cyclopentenyl) imidoyl halides by cyclization of vinyl cation intermediates, followed by halide capture. Utilization of the cyclic products was demonstrated by the synthesis of N-alkenyl amides, amidines, isoquinolines, and tetrazoles or by the subsequent modification of the cyclopentene ring.

Recent advances in synthesis and anticancer potential of triazole containing scaffolds

Cancer is the most lethal disease that may be found anywhere on the globe. Approximately 10% of individuals die as a result of cancer of various types, with 19.3 million new cancer cases and 10 million deaths expected in 2020. More than 100 medications are commercially available for the treatment of cancer, but only a few candidates have high specificity, resulting in several side effects. The scientific community has spent the past decades focusing on drug discovery. Natural resources are used to isolate pharmaceutically active candidates, which are then synthesized in laboratories. More than 60% of all prescribed drugs are made from natural ingredients. Unique five-membered heteroaromatic center motifs with sulfur, oxygen and nitrogen atoms are found in heterocyclic compounds such as indazole, thiazole, triazole, triazole, and oxazole, and are used as a core scaffold in many medicinally important therapies. Triazole possesses a wide range of pharmacological activities including anticancer, antibacterial, antifungal, antibiotic antiviral, analgesic, anti-inflammatory, anti-HIV, antidiabetic, and antiprotozoal activities. Novel Triazole motifs with a variety of biological characteristics have been successfully synthesized using versatile synthetic methods. We intend here to facilitate the rational design and development of innovative triazole-based anti-cancer medicines with increased selectivity for various cancer cell lines by providing insight into various ligand-receptor interactions.

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.

Base-Induced Highly Regioselective Synthesis of N2-Substituted 1,2,3-Triazoles under Mild Conditions in Air

We developed a highly regioselective base-induced synthesis of N²-substituted 1,2,3-triazoles from N-sulfonyl-1,2,3-triazoles and alkyl bromides/alkyl iodides at room temperature. We propose an S_N2-like mechanistic pathway to explain the high N²-regioselectivity. The protocol features a broad substrate scope and generates products in good to excellent yields (72-90%).

Ligand-dependent stereoselective Suzuki-Miyaura cross-coupling reactions of β-enamido triflates

The stereoselective Suzuki–Miyaura cross-coupling of (Z)-β-enamido triflates is demonstrated. Depending on the nature of the ligand in the palladium catalyst, either retention or inversion of the configuration during the synthesis of β,β-diaryl-substituted enamides is observed. Thus, the method provides synthetic access to both isomers of the target enamides from (Z)-β-enamido triflates.

Access to (Z)-β-Substituted Enamides from N1-H-1,2,3-Triazoles

A direct ring-opening/nucleophilic substitution reaction of N1-H-1,2,3-triazoles has been described. Divergent (Z)-β-halogen- or sulfonyl-substituted enamides could be stereospecifically synthesized in a tunable manner. This strategy might not only enable a new ring-opening method of N1-H-1,2,3-triazoles under nonmetal catalysis and mild reaction conditions but also offer a good opportunity to reliably access versatile (Z)-β-substituted enamides that could be used as synthetic precursors for further synthetic transformations.

Stereoselective Synthesis of (Z)-β-Enamido Fluorides from N-Fluoroalkyl- and N-Sulfonyl-1,2,3-triazoles

A reaction of N-sulfonyl-1,2,3-triazole with boron trifluoride etherate afforded a (Z)-β-ensulfonylamido fluoride instead of the previously erroneously assigned E isomer. The correction of the stereochemistry was based on a ge-1D ROESY NMR experiment and X-ray crystal structure analyses. Application of the reaction to N-fluoroalkyl-1,2,3-triazoles afforded new (Z)-β-enamido fluorides in a stereoselective manner. A mechanism involving coordination of BF₃ with the triazole ring and vinyl diazonium and vinyl cation intermediates was proposed.