Ring‐Expanded N‐Heterocyclic Carbenes for Copper‐Mediated Azide–Alkyne Click Cycloaddition Reactions

Abstract

A series of well‐defined copper(I) complexes bearing ring‐expanded N‐heterocyclic carbene (NHC) ligands has been applied to the azide–alkyne cycloaddition reaction. The obtained results notably showed that the six‐membered NHC ligands outperform well‐established five‐membered ones. [CuI(Mes‐6)] displayed a remarkable catalytic activity while respecting the strict criteria for click reactions.

The first ring-expanded NHC–copper(i) phosphides as catalysts in the highly selective hydrophosphination of isocyanates

“…[24][25][26] RE-NHCcopper(I) complexes such as copper(I) halides and copper(I) alkoxides have been established as having enhanced catalytic activity over their five-membered ring counterparts. [27][28][29] We thus set out to synthesise and characterise a range of low-coordinate copper phosphide species supported by both 5-and 6-membered NHCs in order to evaluate their potential as catalytic intermediates. Herein we report the rational synthesis of four (NHC)CuPPh 2 compounds (NHC = IPr, 6-Dipp, SIMes and 6-Mes), including the first examples of RE-NHC copper phosphides.…”

Alkynyl‐ or Azido‐Functionalized 1,2,3‐Triazoles: Selective MonoCuAAC Promoted by Physical Factors

“…In both cases (solvent‐based and neat approaches), the CuAAC reaction is efficiently catalyzed by N‐heterocyclic carbene (NHC) copper(I) complexes. We selected the most catalytically active (NHC)CuX complexes under solvent‐free or apolar conditions: SIMesCuBr ( 1 a ), (6‐Mes)CuBr ( 1 b ), (7‐Mes)CuBr ( 1 c ), abnormal NHC complex (aNHC)CuCl ( 1 d ), (Naph‐8‐Mes)CuBr ( 1 e ) and well‐soluble in apolar media fluorinated (F‐NHC)CuCl ( 1 f) and tested them in the model reaction between phenylacetylene and p ‐tolylazide under following conditions: 1) heptane, 40 °C, 2) neat, 40 °C (Scheme ). The choice of reaction temperature is motivated by the fact that even daily fluctuations in temperature can alter the solubility of the reaction components leading to reproducibility issues; therefore, the temperature slightly higher than RT was chosen.…”

Copper-azide nanoparticle: a ‘catalyst-cum-reagent’ for the designing of 5-alkynyl 1,4-disubstituted triazoles

“…The azide-alkyne cycloaddition reaction between carbon nanotube functionalized azide containing polymer and alkyne molecule has been reported using copper acetate as an efficient catalyst 14 . A Cu(I)-N‐heterocyclic carbene framework has been applied for the azide-alkyne cycloaddition reaction and it was established that six‐membered NHC ligands showed superior performance for the preparation of 1,4‐disubstituted triazoles as compared with the five‐membered one 15 . A Cu(I)‐catalyzed three component (terminal alkynes, azides, and propargylic carbonate) reaction exhibited the formation of 1,3,5‐trisubstituted triazoles (5‐allenyl‐1,2,3‐triazoles) with a high yield 16 .…”