Access to Fluoroalkylated Azoles and 2-Acylaminoketones via Fluorinated Anhydride-Mediated Cleavage of NH-1,2,3-Triazoles

Bioorthogonal Cycloadditions of C3-Trifluoromethylated 1,2,4-Triazines with trans-Cyclooctenes

1,2,4-triazines are a valuable class of heterodienes that can be employed in inverse electron-demand Diels-Alder reactions. However, their broader application in bioorthogonal chemistry is limited due to their low reactivity. This article focuses on 3-(trifluoromethyl)-1,2,4-triazines, which can be efficiently prepared in a one-pot reaction from NH-1,2,3-triazoles. These triazines are highly reactive in reactions with strained cyclooctenes, giving second-order rate constants as high as 230 M-1 s-1. Despite their high reactivity, the compounds remain sufficiently stable under biologically relevant conditions. We show that some of the compounds are fluorogenic, a property of potential use in bioimaging. In addition, we demonstrate the successful application of the triazines in labeling model biomolecules. Our work shows that the reactivity of 1,2,4-triazines can be enhanced by the 3-CF3-substitution, which we consider an important step toward the wider use of this promising class of reagents.

Copper Loading-Controlled Selective Synthesis of 2,5-Bis(trifluoromethyl) and Monotrifluoromethyl-Substituted Oxazoles

A general domino annulation reaction of sulfonylmethyl isocyanide with trifluoroacetic anhydride in the presence of copper chloride as an additive is developed. The reaction affords 2,5-bis(trifluoromethyl)oxazoles in modest to good yields under mild conditions. A wide variety of sulfonylmethyl isocyanide and perfluorocarboxylic anhydride substrates are amenable to this transformation. Under a higher copper salt loading conditions, the reaction led to the formation of monotrifluoromethyl-substituted oxazole product.

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.

Microwave-assisted Synthesis of Fluorinated Heterocycles

Abstract:

The diverse biological applications of fluorinated heterocycles make them crucial chemical compounds. Several synthetic processes have been developed for their synthesis. Microwave-assisted synthesis has emerged as an important technique for generating fluorinated heterocycles in an eco-friendly and energy-efficient manner. It provides several benefits like less reaction time, high reaction yield, homogeneous heat distribution leading to lower side reaction, and better control of reaction temperature. Recently there has been significant progress in microwave use for heterocycle synthesis. This article discusses the applications of microwave irradiation in the synthesis of oxygen- and nitrogen-containing fluorinated heterocycles.

Silver-Catalyzed Cascade Cyclization of Amino-NH-1,2,3-Triazoles with 2-Alkynylbenzaldehydes: An Access to Pentacyclic Fused Triazoles

An operationally simple Ag(I)-catalyzed approach for the synthesis of isoquinoline and quinazoline fused 1,2,3-triazoles was developed by a condensation and amination cyclization cascade of amino-NH-1,2,3-triazoles with 2-alkynylbenzaldehydes involving three new C-N bond formations in one manipulation, in which the group of -NH of the triazole ring serves as a nucleophile to form the quinazoline skeleton. The efficient protocol can be applied to a variety of substrates containing a range of functional groups, delivering novel pentacyclic fused 1,2,3-triazoles in good-to-excellent yields.

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.