Copper-Catalyzed Synthesis of 5-Carboxyl-4-perfluoroalkyl Triazoles

A facile, scalable synthesis of previously inaccessible trifluoromethyl and perfluoroalkyl triazoles is disclosed. Mediated by copper, this catalytic protocol enables access to 4-perfluoroalkyl triazoles from commodity chemicals. A catalytic Cu(II) system wherein copper serves two roles (generation of N-tosyl-2-vinyldiazenes and N-N bond formation) allows for rapid assembly of 5-carboxyl-4-perfluoroalkyl-triazoles from N-tosylhydrazide and perfluoroalkyl acetoacetates. Ethyl 4,4,4-trifluoro-3-(2-tosylhydrazineylidene)butanoate, a previously unknown air and bench stable reagent for access to CF₃-triazoles, was developed to enable this chemistry. This led to the identification of a series of crystalline hydrazone reagents that could be used as templates to construct an array of triazoles. Hydrolysis and decarboxylation parlay this approach into a means to access 5-H-4-CF₃-triazoles. The approach exhibits high functional group tolerance and can be executed on a multigram scale.

Bioactive 1,2,3-Triazoles: An Account on their Synthesis, Structural Diversity and Biological Applications

The triazole heterocycle is a privileged scaffold in medicinal chemistry, since its structure is present in a large number of biologically active molecules, including several drugs currently in the market. Due to their vast applications, a wide variety of methods are described for their preparation, such as the 1,3-dipolar cycloaddition and processes involving diazo compounds and diazo transfer reactions. Considering the significant number of contributions from our research group to this chemistry in recent decades, in this account we discuss both the development of new methods for the synthesis of 1,2,3-triazoles and the preparation of new triazole-functionalized biologically active molecules using classical approaches.

Direct Transformation of Terminal Alkynes into Amidines by a Silver-Catalyzed Four-Component Reaction

An unprecedented conversion of terminal alkynes into N-sulfonimidamides (amidines) is reported by a silver-catalyzed, one-pot, four-component reaction with TMSN₃, sodium sulfinate, and sulfonyl azide. The reaction scope includes both aromatic and aliphatic alkynes. A possible cascade reaction mechanism, consisting of alkyne hydroazidation, sulfonyl radical addition, 1,3-dipolar cycloaddition by TMSN₃, and retro-1,3-dipolar cycloaddition, is proposed. TMSN₃ is found to play an essential role in each step of the reaction.

An efficient one-pot strategy for the highly regioselective metal-free synthesis of 1,4-disubstituted-1,2,3-triazoles

A simple and efficient metal-free methodology for the regioselective synthesis of 1,4-disubstituted-1,2,3-triazoles by applying a novel inverse electron-demand-1,3-dipolar cycloaddition approach has been developed.