Regioselective synthesis of [1,2,3]-triazoles catalyzed by Cu(I) generated in situ from Cu(0) nanosize activated powder and amine hydrochloride salts

Click Chemistry, A Powerful Tool for Pharmaceutical Sciences

“…Sodium ascorbate is typically used as the reducing agent in a 3-to 10-fold excess (3), but other reducing agents, including hydrazine (13) and tris(2-carboxyethyl)phosphine (TCEP) (9), have been used with reasonable success. The advantages of this strategy are it is cheap, it can be performed in water, and it does not require deoxygenated atmosphere (3,14). Not only does an aqueous solvent remove the need for a base, as previously explained, but it also eliminates the need for protecting groups (O-H and N-H functional groups essentially remain "invisible" in aqueous solutions) and it is environmentally safe (1) This method does not require a reducing agent, but it has to be done in a deoxygenated environment and in an organic solvent (or a mixed solvent), meaning that protection groups will probably be needed along with a base (14).…”

“…The advantages of this strategy are it is cheap, it can be performed in water, and it does not require deoxygenated atmosphere (3,14). Not only does an aqueous solvent remove the need for a base, as previously explained, but it also eliminates the need for protecting groups (O-H and N-H functional groups essentially remain "invisible" in aqueous solutions) and it is environmentally safe (1) This method does not require a reducing agent, but it has to be done in a deoxygenated environment and in an organic solvent (or a mixed solvent), meaning that protection groups will probably be needed along with a base (14). It has been shown that using excess amounts of both the bases 2,6-lutidine and DIPEA produce the best results, causing the least amount of side products (6,12).…”

“…Still, Cu I salts are not as reliable as the Cu II procedure (6). Oxidizing copper metal with an amine salt is another way to generate the catalyst (7,14). There are a considerable number of disadvantages with this strategy.…”

New routes to Cu(i)/Cu nanocatalysts for the multicomponent click synthesis of 1,2,3-triazoles

“…In spite of this, processing costs and the search for new combinations of benecial properties have led to continued interest in the replacement of established noble metal nanocatalysts with those of relatively inexpensive metals. 12 In this vein, nanoparticulate copper has recently been deployed in various chemical syntheses, this having been enabled by the development of routes to the preparation of the copper-based nanomaterials Cu(0), [13][14][15][16] CuO and Cu 2 O. 17,18 As a result, copper nanoparticles (Cu NPs) have found many applications in, amongst other reactions, the reduction of functional groups, 19 the formation of carbon-carbon and carbon-nitrogen bonds, 20 and in so-called "click" chemistry.…”

Immobilization of Porphyrinatocopper Nanoparticles onto Activated Multi‐Walled Carbon Nanotubes and a Study of its Catalytic Activity as an Efficient Heterogeneous Catalyst for a Click Approach to the Three‐Component Synthesis of 1,2,3‐Triazoles in Water

“…Sharpless et al [15] utilized Cu(I)-catalyzed azidealkyne cycloaddition (CuAAC), [16] one of the most reliable click reactions [17] to prepare triazoles using in situ generated Cu(I) from copper sulphate and sodium ascorbate, a stoichiometric amount of copper turnings in water and Cu(I) with stabilizing ligands at room temperature (Scheme 1, b). Nanopowders and copper nanoclusters [18,19] as well as Cu(I) salts [20] in the presence of nitrogen bases were also used for the synthesis of 1,2,3-triazoles, whereas in the former process the formation of side products, bis-triazoles and diacetylenes, was observed. N-heterocyclic copper carbene complexes have also been reported for the cycloaddition reaction of azide and alkynes.…”