Protected N-heterocyclic carbenes as latent organocatalysts for the low-temperature curing of anhydride-hardened epoxy resins

Altmann, Hagen J.; Naumann, Stefan; Buchmeiser, Michael R.

doi:10.1016/j.eurpolymj.2017.05.032

Cited by 11 publications

(12 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This reaction offers a controlled route to polyesters, although it has been much less studied than ring‐opening polymerization of cyclic esters . ROCOP generally requires organometallic initiators to reach efficient curing, but the use of NHC was reported very recently . In a model copolymerization, the as‐irradiated azolium salt / ITX mixture (1/1 equiv) was added to a mixture of cyclohexene oxide (CHO, 500 equiv) and phthalic anhydride (PA, 100 equiv) (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

“…As a result, the five main populations of peaks were all assigned to α‐methyl‐ω‐hydroxyl OH/CH 3 ‐terminated polymers. The mechanism was presumed to proceed through a nucleophilic attack of NHCs on anhydride functionality (Scheme S2) . Besides, copolymers (entries a and b) exhibited monomodal SEC traces with narrow molecular weight distributions ( Đ ≈1.2, see Figure S11).…”

Section: Resultsmentioning

confidence: 99%

“…[53,54] ROCOP generally requires organometallic initiatorst or each efficientc uring, but the use of NHC was reported very recently. [55,56] In am odel copolymerization, the as-irradiateda zolium salt/ITX mixture (1/1 equiv) was added to am ixture of cyclohexene oxide (CHO,5 00 equiv) andp hthalic anhydride (PA, 100 equiv) (Scheme 7). Polymerization was conducted at 110 8C using thus CHO as both the monomer and the solvent.…”

Section: Synthesis Of Polyestermentioning

confidence: 99%

“…The mechanism was presumed to proceed through an ucleophilic attack of NHCs on anhydride functionality (Scheme S2). [55,56] Besides, copolymers (entriesa and b) exhibitedm onomodalS EC traces with narrow molecular weight distributions( % 1.2, see Figure S11). Surprisingly, 1H + + BPh 4 À À showeds lightly higher conversionsa nd M n values than 1 despite incomplete deprotonation, raising doubts about the role of other photoproductsi nr eactionc atalysis.…”

Section: Entrymentioning

confidence: 99%

See 3 more Smart Citations

Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis

Trinh

Malval

Morlet‐Savary

et al. 2019

Chemistry A European J

View full text Add to dashboard Cite

In the search of smarter routes to control the conditions of N‐heterocyclic carbene (NHCs) formation, a two‐component air‐stable NHC photogenerating system is reported. It relies on the irradiation at 365 nm of a mixture of 2‐isopropylthioxanthone (ITX) with 1,3‐bis(mesityl)imidazoli(ni)um tetraphenylborate. The photoinduced liberation of NHC is evidenced by reaction with a mesitoyl radical to form an NHC‐radical adduct detectable by electron spin resonance spectroscopy. The NHC yield can be determined by 1H NMR spectroscopy through the formation of a soluble and stable NHC–carbodiimide adduct. To deprotonate the azolium salt and liberate the NHC, a mechanism is proposed in which the role of base is played by ITX radical anion formed in situ by a primary photoinduced electron‐transfer reaction between electronically excited ITX (oxidant) and BPh4− (reductant). An NHC yield as high as 70 % is achieved upon starting with a stoichiometric ratio of ITX and azolium salt. Three different photoNHC‐mediated polymerizations are described: synthesis of polyurethane and polyester by organocatalyzed step‐growth polymerization and ring‐opening copolymerization, respectively, and generation of polynorbornene by ring‐opening metathesis polymerization using an NHC‐coordinated Ru catalyst formed in situ.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Synthesis Of Polyestermentioning

confidence: 99%

Section: Entrymentioning

confidence: 99%

See 2 more Smart Citations

Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis

Trinh

Malval

Morlet‐Savary

et al. 2019

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…So far, a wide variety of thermal latent initiators have been developed. The recent examples involve N ‐acylimidazoles, adducts of carbenes with CO 2 , hydroxy amides, derivatives of 4‐aminopyridine, and metal xanthates . Besides, onium salts have been most frequently used because of the easy preparation and the resultant structural diversity that allows appropriate choice of initiator from the libraries .…”

Section: Introductionmentioning

confidence: 99%

Construction of excellent thermal latent system for the synthesis of networked epoxide polymers by sulfonium salts

Kawaoka

Koge

Sudo

et al. 2018

J. Polym. Sci. Part A: Polym. Chem.

View full text Add to dashboard Cite

An efficient thermally latent initiation system using dual sulfonium salts, consisting S‐benzylsulfonium salt 1 bearing SbF6− counter anion and S,S‐dimethylsulfonium salt 2 bearing CH3 SO4− counter anion, has been developed for the cationic polymerization of epoxides. Compared to the conventional system using 1 as a thermally latent initiator, the newly developed system allowed significant improvement of stability of epoxy formulations during storage at ambient temperature without sacrificing their curability at elevated temperatures. Such a remarkable performance is attributable to the nucleophilic attack of CH3 SO4− to cationic species formed unavoidably by the reaction of 1 with epoxide. Such entrapment of cationic species into the corresponding dormant led to the inhibition of undesirable chain growth of polymers during storage of epoxy formulations. In addition, the dormant can undergo dissociation at elevated temperature to give cationic species, which can readily initiate the polymerization of epoxide. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2096–2102

show abstract

The Chemistry of Azolium‐Carboxylate Zwitterions and Related Compounds: a Survey of the Years 2009–2020

Delaude

2020

Adv Synth Catal

View full text Add to dashboard Cite

This review highlights the most significant advances that were accomplished in the chemistry of azolium‐carboxylate betaines within the years 2009–2020. Whenever needed, prior, seminal achievements are also briefly recalled to help put recent developments in a broader perspective. The compounds under scrutiny are zwitterions obtained upon nucleophilic addition of N‐heterocyclic carbenes (NHCs) onto carbon dioxide. We first present an overview of the various synthetic paths that give access to these inner salts before discussing their stability. The main part of this report then summarizes the numerous applications relying on NHC ⋅ CO2 zwitterions employed either in stoichiometric or catalytic proportions in the fields of organometallic chemistry and homogeneous catalysis, organic synthesis and organocatalysis, polymer chemistry, and materials science. A particular emphasis is placed on the endeavors devoted to trap carbon dioxide and to convert this greenhouse gas into valuable chemicals via the intermediacy of NHC ⋅ CO2 zwitterions. Whenever available, mechanistic considerations that help assess the pivotal role played by these species in CO2 activation are discussed. Because of their close relationship with azolium‐carboxylate betaines, azolium hydrogencarbonate salts and azolium‐methylenecarboxylate zwitterions resulting from the addition of carbon dioxide onto N‐heterocyclic olefins (NHOs) are included in this survey, which also covers the reactivity of carbon monoxide toward NHCs and related carbene species.magnified image

show abstract

Protected N-heterocyclic carbenes as latent organocatalysts for the low-temperature curing of anhydride-hardened epoxy resins

Cited by 11 publications

References 57 publications

Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis

Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis

Construction of excellent thermal latent system for the synthesis of networked epoxide polymers by sulfonium salts

The Chemistry of Azolium‐Carboxylate Zwitterions and Related Compounds: a Survey of the Years 2009–2020

Contact Info

Product

Resources

About