Atom transfer coupling reactions performed with benign reducing agents and radical traps

Xia, Katherine; Rubaie, Alia J.; Johnson, Brendan; Parker, Samantha A.; Tillman, Eric S.

doi:10.1002/pola.29482

Cited by 9 publications

(4 citation statements)

References 62 publications

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“…Using MNP as the radical trap produced slightly greater extents of coupling reaching approximately 90%. For both NBz and MNP, an increase in coupling was only observed when the ratio of metals and ligands increased, which is consistent with previous studies [21,22] (Trial 19 versus Trial 20 and Trial 23 versus Trial 24). Figure 4 shows GPC traces of the PSBr precursor (blue) and the coupled product (orange), with a clear shift to shorter elution volumes and only a small amount of unreacted precursor remaining (Table 3, Trial 25).…”

Section: Resultssupporting

confidence: 92%

“…i Extent of coupling, as calculated by 2(1-Mnprecursor/Mncoupled). Finally, we focused on PSBr, chosen last because of its ability to be coupled under a wider assortment of ATRC-type reactions, including no radical trap at all [6,8,[20][21][22][23][24]. Thus, we were able to simply retest conditions applied above using PMA and PMMA to join brominated PS chains (Table 3), also prepared using ATRP.…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, the bulky PMMA radicals, which favor disproportionation, require radical trap-assistance to undergo substantial dimerization [12,19]. On the other hand, PS radicals can be successfully coupled into dimers [6,8,[20][21][22][23][24] or macrocycles [10,20,25] under a wider range of ATRC-type conditions and are less sensitive to the presence [21,22] or structure of a radical trap [26]. Since applicability across all classes was a defined requirement, radical traps were used in all coupling reactions.…”

Section: Introductionmentioning

confidence: 99%

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Universal Chain-End Coupling Conditions for Brominated Polystyrenes, Polyacrylates, and Polymethacrylates

Andry

Lee

et al. 2021

Processes

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Atom transfer radical coupling (ATRC), performed with or without radical traps, has allowed for high extents of coupling (Xc) for a variety of brominated polymers, yet structurally different polymeric chain ends require unique reagents and reaction conditions. Inspired by a similar study that focused on universal conditions for the controlled polymerization of different monomers using atom transfer radical polymerization (ATRP), this work focuses on developing a single set of conditions (or conditions with as little variation as possible) that will achieve extents of coupling greater than 80% or end-brominated chains of polystyrene (PSBr), poly(methyl methacrylate) (PMMABr), and poly(methyl acrylate) (PMABr). The radical traps α-phenyl-tert-butylnitrone (PBN), 2-methyl-2-nitrosopropane (MNP), and nitrosobenzene (NBz) were chosen in this study, along with copper catalysts, reducing agents, and nitrogen-based ligands. Ultimately, a single set of effective reaction conditions was identified with the only difference being the radical trap used: MNP was effective for coupling PSBr and PMABr while NBz was necessary to achieve similarly high extents of coupling for PMMABr.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Universal Chain-End Coupling Conditions for Brominated Polystyrenes, Polyacrylates, and Polymethacrylates

Andry

Lee

et al. 2021

Processes

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“…[23][24][25] High-molecular-weight AAs based on spin traps with symmetric structure can also be obtained using radical trap-assisted atom transfer radical coupling (RTA-ATRC). [26][27][28][29][30][31][32][33][34] The technique involves the synthesis of a polymer with a particular structure and MW characteristics in the ATRP regime followed by coupling of highmolecular-weight radicals mediated by nitrones or nitroso compounds in the presence of a catalytic system based on transition metals.…”

mentioning

confidence: 99%

Structural and hydrodynamic characteristics of polystyrene synthesized in the presence of conjugated dinitrones

et al. 2021

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A series of branched high-molecular-weight alkoxyamines (HAAs) based on polystyrene of diff erent molecular weight were synthesized using nitroxide radicals generated in situ in the presence of conjugated dinitrones (N,N-dimethylglyoxaldinitrone, N,N-di-tert-butylglyoxaldinitrone, and N,N-diphenylglyoxaldinitrone). Structural features of the products obtained were studied by MALDI-TOF mass spectrometry. Modifi cation of the synthesized HAAs in the presence of azobisisobutyronitrile, carbon tetrabromide, dodecyl mercaptane, 4,5,5-trimethyl-2,2-diethyl-2,5-dihydroimidazole-1-oxyl, and 3,5-di-tert-butylbenzoquinone, as well as thermolysis of the HAAs in the presence of atmospheric oxygen showed that the nitroxide fragments are located within the polymer chain irrespective of the initial structure of the conjugated dinitrone. The molecular weight characteristics and conformational properties of the nitroxidecontaining linear macromolecules and polymers were studied by static and dynamic light scattering and by viscometry. In most cases, the calculated values of the ρ-parameter (R g /R h ) and the Zimm viscosity factor of the branched polystyrene samples synthesized using conjugated dinitrones are lower than those of linear analogues.

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“Greener” Coupling of Poly(methyl methacrylate) and Poly(methyl acrylate) Chains using Activators Generated by Electron Transfer and Radical Traps

Xia

Rubaie

Johnson

et al. 2020

Macro Chemistry & Physics

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Monobrominated versions of poly(methyl methacrylate) (PMMABr) and poly(methyl acrylate) (PMABr) are prepared by atom transfer radical polymerization and subjected to a variety of chain end‐coupling reactions, with the goal of achieving high extents of coupling with minimal metal content. By using atom transfer radical coupling (ATRC) with radical trap assistance in conjunction with activators generated by electron transfer, high extents of coupling (Xc) could be achieved for both polymer classes without requiring copper(I) as an initial reactant, and replacing elemental copper with environmentally benign reducing agents (Xc > 0.85). Specifically, the highest extents of coupling are observed with ascorbic acid as the reducing agent along with copper(II) bromide as the pre‐catalyst. Overall, similar extents of coupling are observed while using ≈1% of the total metal of a traditional ATRC reaction for PMABr and ≈3% for PMMABr.

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Atom transfer coupling reactions performed with benign reducing agents and radical traps

Cited by 9 publications

References 62 publications

Universal Chain-End Coupling Conditions for Brominated Polystyrenes, Polyacrylates, and Polymethacrylates

Universal Chain-End Coupling Conditions for Brominated Polystyrenes, Polyacrylates, and Polymethacrylates

Structural and hydrodynamic characteristics of polystyrene synthesized in the presence of conjugated dinitrones

“Greener” Coupling of Poly(methyl methacrylate) and Poly(methyl acrylate) Chains using Activators Generated by Electron Transfer and Radical Traps

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