The Catalytic Activity of Carbon-Supported Cu(I)-Phosphine Complexes for the Microwave-Assisted Synthesis of 1,2,3-Triazoles

Abstract

A set of Cu(I) complexes with 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo-[3.3.1]nonane (DAPTA) phosphine ligands viz. [CuX(κP-DAPTA)3] (1: X = Br; 2: X = I) and [Cu(μ-X)(κP-DAPTA)2]2 (3: X = Br; 4: X = I) were immobilized on activated carbon (AC) and multi-walled carbon nanotubes (CNT), as well as on these materials after surface functionalization. The immobilized copper(I) complexes have shown favorable catalytic activity for the one-pot, microwave-assisted synthesis of 1,2,3-triazoles via the azide-alkyne cycloaddition reaction (CuAAC). The heterogenized systems with a copper loading of only 1.5–1.6% (w/w relative to carbon), established quantitative conversions after 15 min, at 80 °C, using 0.5 mol% of catalyst loading (relative to benzyl bromide). The most efficient supports concerning heterogenization were CNT treated with nitric acid and NaOH, and involving complexes 2 and 4 (in the same order, 2_CNT-ox-Na and 4_CNT-ox-Na). The immobilized catalysts can be recovered and recycled by simple workup and reused up to four consecutive cycles although with loss of activity.

Synthesis of a Novel Series of Cu(I) Complexes Bearing Alkylated 1,3,5-Triaza-7-phosphaadamantane as Homogeneous and Carbon-Supported Catalysts for the Synthesis of 1- and 2-Substituted-1,2,3-triazoles

“…Our catalyst is inferior to C/Cu NPs in the sense that it requires a higher temperature (125 • C) but superior in the sense that the catalyst preparation is quite easy and the time of reaction is much shorter (60 min). In our recent publication using Cu(I)-DAPTA complex supported on CNT-ox-Na as catalyst, only 48% yield was obtained at 80 • C for a period of 15 min using 1 mol % catalyst loading [28]. Our present system does not require any reducing agent and the reaction proceeds in high-good yields (99% in homogeneous system using 5b, and 80% using 5b_CNT-ox-Na) at low catalyst loading (5 mol% of 5b or 1.2 mol % of 5b_CNT-ox-Na).…”

“…The coordination properties of the obtained phosphane molecules have been studied towards copper(I) to produce a novel set of hydrophilic Cu(I) complexes. In continuation of our contribution to the field of click chemistry by means of homogeneous [12,22,23,26,41] and carbon-supported catalysts [28], the three-component approach of the CuAAC reaction for microwave-assisted synthesis of 1,4-disubstituted-and 2-hydroxymethyl-1,2,3-triazoles in aqueous medium is tackled using the new Cu(I) complexes as catalysts in a homogenous system, and as heterogenized catalysts supported on activated carbon (AC) and multi-walled carbon nanotubes (CNT), thus aiming also a comparison between both catalysis methods and these types of carbon supports.…”

“…The immobilization of 5a and 5b on the carbon materials can occur by interaction of the Cu(I) complexes with the oxygenated functional groups of the carbon matrix, via possible formation of a Cu-O bond upon displacement of the halo (X) ligand (Figure S69), addition of one of these groups to the Cu atom (Figure S70), or a non-covalent interaction such as H-bonding (Figure S71) or ionic interaction (Figure S72). When compared to their copper(I) analogues bearing a neutral PTA derivative (i.e., 3,7-diacetyl-1,3,7-triaza-5phosphabicyclo-[3.3.1]nonane) [28], complexes 5a and 5b exhibit higher heterogenization values on the same activated carbon materials due to the intermolecular charge interaction between the negatively charged carboxylate groups of the carbon matrix and the positively charged ligand 2 (Figure S72).…”

“…The hydrosoluble phosphanes of the type 1,3,5-triaza-7-phosphaadamantane (PTA) and its derivatives are among the most useful water-soluble phosphines in the field of organometallic chemistry and catalysis [24,25]. As a result of our interest in copper complexes based on PTA and its derivatives, we have recently reported water-soluble copper complexes with a high catalytic activity towards the CuAAC reaction in aqueous media [12,[26][27][28]. Utilization of hydrosoluble copper complexes for CuAAC offers the possibility of being easily separable from the obtained organic triazoles by simple water washing to provide the product with high purity [12,23,26].…”

Heterogeneous Gold Nanoparticle-Based Catalysts for the Synthesis of Click-Derived Triazoles via the Azide-Alkyne Cycloaddition Reaction

“…The 1,2,3-triazoles are prominent nitrogen-containing heterocyclic motifs that have widespread applications in areas ranging from medicinal chemistry to materials science [20][21][22][23]. Although elegant preparative methods for such motifs have been reported [24][25][26][27][28][29][30], versatile and practical methodologies for the synthesis of substituted 1,2,3-triazoles beyond the use of copper-based catalysts are still desirable. Despite the advent of effective non-copper catalysts (i.e., Ru, Ag, Ir) [31,32] which have also demonstrated to catalyze the azide-alkyne cycloaddition (AAC) reaction, additional robust catalytic systems that can provide complementary selectivity or relative reactivity to the copper catalyzed AAC remain in high demand.…”