A-21·CuI as a catalyst for Huisgen’s reaction: about iodination as a side-reaction

Metal-catalyzed azide-alkyne “click” reactions: Mechanistic overview and recent trends

“…A key advantage of this catalyst [35] compared to Sharpless catalyst is the tremendeous ligand acceleration of the reaction. Other recent well-defined supramolecular catalytic approaches for the CuAAC reactions such as polymer-supported catalysts of Cu(I)-poly(styrene-co-maleimide) (CuI-SMI) for the one-pot three-component click synthesis of 1,4-disubstituted-1H-1,2,3-triazoles [138], polymer-anchored PS-C22-CuI for three-component synthesis of 1,4-disubstituted 1,2,3-triazoles under aerobic conditions in water [173], polymersupported catalyst Amberlyst A-21-CuI for the synthesis of 1,4-disubstituted-1H-1,2,3-triazoles in CH 2 Cl 2 at r.t. [174], Cu(I)-incorporated microporous Schiff base network polymer for CuAAC in MeCN at r.t. [175], supramolecular material of polymer supported Cu(I) catalyst, (Cu(I)-poly(2-aminobenzoic acid), Cu(I)-pABA), showed excellent yield toward AAC reactions at r.t. in aqueous media [176]. The combined use of two polymer supported reagents (polystyrene-1,5,7-triazabicyclo[4,4,0]dec-5-ene/Cu and polystyrene-2-iodoxybenzamide) enabled the reliable CuAAC in the presence of an oxidant agent [177], CuI onto dimethylaminografted cross-linked polystyrene (CuI@A-21) for azide-alkyne click polymerization [178], and metal-organic framework (Cu-MOF, Cu(PTZ)(NSA) 0.5 ·H 2 O) for the solvent-free CuAAC [179], were also successfully achieved.…”

Recent Advances in Recoverable Systems for the Copper-Catalyzed Azide-Alkyne Cycloaddition Reaction (CuAAC)

“…[88,89]). Occasional observations of C-5 iodinated triazole by-products in the cycloaddition process catalyzed by A-21/CuI led the same group to investigate the possible causes of such a side-reaction [155]. After examining various factors, potential mistakes were identified in the preparation of the supported catalyst and in the conduct of CuAAC runs, which result in the obtainment of substantial amounts of iodinated triazoles (up to 12 mol %).…”

1,2,3- Triazoles: general and key synthetic strategies

“…However, in some cases, this heterogeneous catalyst led to the formation of 5-iodotriazole. 148 Scheme 23. First report of CuI immobilization on Amberlyst A-21 in the catalysis of CuAAC reactions.…”