A new simplified protocol for copper(I) alkyne–azide cycloaddition reactions using low substoichiometric amounts of copper(II) precatalysts in methanol

Copper(II) carboxylates are reduced efficiently by methanol in the presence of alkynes and form yellow alkynylcopper(I) polymeric precatalysts that are involved with azides, in the absence of added ligands, in the catalytic cycles that result in the formation of 1,4-disubstituted 1,2,3-triazoles

"Copper-in-charcoal" revisited: delineating the nature of the copper species and its role in catalysis

"Copper-in-charcoal" has been shown to be a versatile catalytic source of supported copper for a variety of important synthetic transformations, as well as in other fields such as energy. We herein report the characterization of this material and the implications that its preparation has on catalysis, thus providing a greater understanding of the scope and limitations of this catalyst system. (Chemical Equation Presented)

Experimental evidence for the involvement of dinuclear alkynylcopper(I) complexes in alkyne-azide chemistry

Dinuclear alkynylcopper(I) ladderane complexes are prepared by a robust and simple protocol involving the reduction of Cu2(OH)3OAc or Cu(OAc)2 by easily oxidised alcohols in the presence of terminal alkynes; they function as efficient catalysts in copper-catalysed alkyne–azide cycloaddition reactions as predicted by the Ahlquist–Fokin calculations. The same copper(I) catalysts are formed during reactions by using the Sharpless–Fokin protocol. The experimental results also provide evidence that sodium ascorbate functions as a base to deprotonate terminal alkynes and additionally give a convincing alternative explanation for the fact that the CuI-catalysed reactions of certain 1,3-diazides with phenylacetylene give bis(triazoles) as the major products. The same dinuclear alkynylcopper(I) complexes also function as catalysts in cycloaddition reactions of azides with 1-iodoalkynes

Mannich reactions of alkynes: mechanistic insights and the role of sub-stoichiometric amounts of alkynylcopper(I) compounds in the catalytic cycle

Yellow polymeric alkynylcopper(I) compounds observed in the three-component Mannich reactions of alkynes, secondary amines and aldehydes are shown to be pre-catalysts that give rise to catalytic copper(I) alkyne complexes by interaction with secondary amines (see scheme). Interaction of these complexes with iminium ions (formed from aldehydes or their equivalents, including CH2Cl2), results in the formation of Mannich bases in high yields

Alkynylcopper(I) polymers and their use in a mechanistic study of alkyne-azide click reactions

Polymeric dinuclear alkynylcopper(I) complexes, for example phenylethynylcopper(I), can be prepared by a robust method involving the interaction of terminal alkynes with copper(II) salts in acetonitrile. The use of the ladder polymers provides heterogeneous catalysts for copper-catalyzed azide–alkyne cycloaddition (CuAAC) reactions and provides important mechanistic information

“Copper-in-Charcoal” Revisited: Delineating the Nature of the Copper Species and Its Role in Catalysis

“Copper-in-charcoal” has been shown to be a versatile catalytic source of supported copper for a variety of important synthetic transformations, as well as in other fields such as energy. We herein report the characterization of this material and the implications that its preparation has on catalysis, thus providing a greater understanding of the scope and limitations of this catalyst system