Supported Tris-Triazole Ligands for Batch and Continuous-Flow Copper-Catalyzed Huisgen 1,3-Dipolar Cycloaddition Reactions

Abstract

The lack of supported versions of the tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (TBTA) ligand, suitable for flow-chemistry applications at scale, prompted us to develop a new route for the immobilization of such tris-triazole chelating units on highly cross-linked polystyrene resins. With this aim, the preparation of the known TBTA-type monomer 3 was optimized to develop a high-yield synthetic sequence, devoid of chromatographic purifications at any stage. Then, bead-type (P7) and monolithic (M7) functional resins were obtained by the easy and scalable suspension- or mold-copolymerization of 3 with divinylbenzene. Both types of materials were found to possess a highly porous morphology and specific surface area in the dry state and could be charged with substantial amounts of Cu(I) or Cu(II) salts. After treatment of the latter with a proper reducing agent, the corresponding supported Cu(I) complexes were tested in the copper-catalyzed alkyne-azide cycloaddition reaction (CuAAC). The immobilized catalysts proved active at room temperature and, in batch and with catalyst loadings as low as 0.6 mol%, afforded quantitative conversions within 20 h. Independent of the alkyne structure, extended use of the supported catalyst in flow was also possible. In the reaction of benzylazide and propargyl alcohol, this allowed a total turnover number larger than 400 to be reached.

Nanomagnetic macrocyclic Schiff-base–Mn(ii) complex: an efficient heterogeneous catalyst for click approach synthesis of novel β-substitued-1,2,3-triazoles

“…29–32 The obtained triazoles are precious intermediates in preparing several combinations containing, antioxidants, pharmaceuticals, drugs, agrochemicals, dyes, pesticides and polymers. 33–36…”

“…66–68 They have also emerged as efficient heterogeneous catalytic supports because they can easily bond to several organic linkers and provide higher activity, stability and surface area as compared to homogeneous catalysts. 34,69–71…”

“…[29][30][31][32] The obtained triazoles are precious intermediates in preparing several combinations containing, antioxidants, pharmaceuticals, drugs, agrochemicals, dyes, pesticides and polymers. [33][34][35][36] Green chemistry seeks to nd novel chemical methods for synthesis of the targeted products while decreasing the pollutants that are formed as the by-product during the synthesis process. [37][38][39][40][41][42] Moreover, the main purpose of green chemistry is to achieve benign-by-design materials for a more sustainable future.…”

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

“…Immobilisation of copper catalysts has been further developed; alongside the usage of copper coils, already described by Tranmer and Fülöp [457,458,467,468], other new heterogeneous formats have also been reported [469][470][471][472][473]. As an example, in 2020, a polymer-supported tris-triazole ligand was prepared and utilised for Cu immobilisation [474]. The CuAAC was carried out in a monolith and a packed-bed reactor for comparison, and the latter proved to be more efficient, probably due to a higher contact area.…”

A New Dinuclear Cobalt Complex for Copolymerization of CO2 and Propylene Oxide: High Activity and Selectivity

“…So far, wide attention has been paid to the chemical conversion of CO 2 into high value-added energy, materials and chemical products. The beneficial use of CO 2 including the alternating copolymerization of CO 2 and epoxides to make degradable polycarbonates were popular ( Scheme 1 ), which is considered one of the most potential green polymerization processes [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. In addition, polycarbonates have become important topics because of their environment-friendly properties, such as atom-economy, energy-saving and degradation, as well as their several biomedical and pharmaceutical applications [ 12 ].…”