Copper(I) 1,2,3-Triazol-5-ylidene Complexes as Efficient Catalysts for Click Reactions of Azides with Alkynes

Abstract

Complexes of copper with 1,4-diphenyl, 1,4-dimesityl, and 1-(2,6-diisopropylphenyl)-4-(3,5-xylyl)-1,2,3-triazol-5-ylidene (abnormal NHC = N-heterocyclic carbene) were prepared by consecutive treatment of the corresponding azolium salts with silver oxide and copper chloride. The new CuCl(aNHC) complexes efficiently catalyzed click reactions of azides with alkynes to give 1,4-substituted 1,2,3-triazoles in excellent yields at room temperature with short reaction times. CuCl(TPh) was particularly effective for the reaction between sterically hindered azides and alkynes.

Mesoionic oxides: facile access from triazolium salts or triazolylidene copper precursors, and catalytic relevance

“…It is interesting to note that copper complexes comprising bulky carbene ligands (1,2,3-triazol-5-ylidenes akin to 3 or imidazol-2-ylidnes) were reported to show excellent catalytic activity in this reaction. 9a,21 Indeed,105 when using complex 3a as catalyst precursor, full conversion was observed with the same time frame as for the 2a/CuCl mixture. In light of these results we are not confident in attributing the catalytic activity to the carbene complex 3a.…”

Metal-catalyzed azide-alkyne “click” reactions: Mechanistic overview and recent trends

“…Two distinct mechanistic pathways that proceed through a copper(III) metallacycle or by direct π-activation of the starting iodoalkyne are likely to be competitive with these catalysts [112a]. Other carbene ligands that were recently used with success in catalysis of click reactions include abnormal N-heterocyclic carbenes (aNHCs) [55,114], mesoionic carbenes (MIC) and ring-expanded carbenes (RE-NHCs) [115]. With copper(I) complexes of triazolylidene ligands (Fig.…”

Mitsunobu Reaction of 1,2,3‐NH‐Triazoles: A Regio‐ and Stereoselective Approach to Functionalized Triazole Derivatives

“…The discovery of the copper-catalyzed alkyne/azide cycloaddition ("click" chemistry) [1] earlier this century has clearly advanced the research of 1,2,3-triazoles and made these five-membered heterocycles among the "hottest" compounds in chemistry-, [2] materials-, [3] and biological [4] research during the last decade.…”

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On the occasion of the 10th anniversary of click chemistryThe discovery of the copper-catalyzed alkyne/azide cycloaddition ("click" chemistry) [1] earlier this century has clearly advanced the research of 1,2,3-triazoles and made these five-membered heterocycles among the "hottest" compounds in chemistry-, [2] materials-, [3] and biological [4] research during the last decade.[5] This robust method has been widely applied to various areas as an efficient strategy for combining different functionalities under mild conditions. Recently, driven by the great success of the synthesis of 1,2,3-triazoles, more attentions have been put into investigating the fundamental reactivity of this interesting heterocycle.

[6] Various attractive applications have been reported that are associated with the unique 1,2,3-triazole core structure, including the formation of carbene intermediates [7] and adjusting the transition metal reactivity with triazole ligands.

[8] These studies further extended the versatility of 1,2,3-triazole building blocks.

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