One‐Pot Sequential Azide–Alkyne [3+2] Cycloaddition and Atom Transfer Radical Addition (ATRA): Expanding the Scope of In Situ Copper(I) Regeneration in the Presence of Environmentally Benign Reducing Agent

Synthesis of Functionalized Polytriazoles via One‐Pot Sequential Copper‐Catalyzed Azide–Alkyne [3+2] Cycloaddition and Atom Transfer Radical Addition (ATRA)

“…The motivation for the study of one‐pot sequential reactions involving azide–alkyne [3+2] cycloaddition and atom transfer radical addition54 catalyzed by [Cu II (TPMA)X][X] (TPMA=tris(2‐pyridylmethyl)amine, X=Cl − , Br − ) complexes in the presence of ascorbic acid as a reducing agent was primarily to demonstrate the synthetic usefulness of the catalyst regeneration technique originally developed for mechanistically similar ATRP. The pioneering work in our laboratory on copper‐catalyzed ATRA in the presence of free‐radical diazo initiator AIBN showed a significant reduction in the required catalyst loading with high turnover numbers (TONs) 31.…”

“…6, 21 Similarly, ATRA,46 ATRC46 and ATRP60, 61 reactions also utilize the same reducing agent to regenerate the copper(I) complex, which is needed to start the catalytic cycle by homolytically cleaving the carbon–halogen bond. Therefore, a logical step was taken in combining the two reactions in a one‐pot sequential manner 54. Indeed, reactions with azidopropyl methacrylate and 1‐(azidomethyl)‐4‐vinylbenzene in the presence of a variety of alkynes and alkyl halides, catalyzed by as low as 0.5 mol % of [Cu II (TPMA)X][X] (X=Br − , Cl − ) complex, proceeded efficiently to yield highly functionalized (poly)halogenated esters and aryl compounds containing triazolyl group in almost quantitative yields (>90 %, Scheme ).…”

“… Sequential copper‐catalyzed azide–alkyne [3+2] cycloaddition and atom transfer radical addition (ATRA) 54…”

“…51 The methodology was also successfully extended to one‐pot simultaneous reactions, in which propargyl methacrylate and alkyl azides were reacted to yield highly functionalized and well‐defined polymeric materials 52. 53 Furthermore, our laboratory also initiated the study on sequential reactions involving copper(I)‐catalyzed azide–alkyne [3+2] cycloaddition and mechanistically similar ATRA 54. A wide variety of small organic molecules bearing triazole and halide functionalities have been synthesized.…”

Tris(2-pyridylmethyl)amine Based Ligands in Copper Catalyzed Atom Transfer Radical Addition (ATRA) and Polymerization (ATRP)

“…For example, it is widely used as a chelator in copper and/or iron complexes that mimic certain metalloenzymes of relevance to oxygen activation (12,(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). Furthermore, a number of metal complexes with TPMA have also been shown to be active in C-H and O-O activation of small molecules (26)(27)(28)(29)(30)(31)(32), as well as [3+2] azide-alkyne cycloaddition (33)(34)(35)(36)(37)(38).…”