Protonated Phosphazenes: Structures and Hydrogen‐Bonding Organocatalysts for Carbonyl Bond Activation

Jardel, Damien; Davies, Clotilde; Peruch, Frédéric; Massip, Stéphane; Bibal, Brigitte

doi:10.1002/adsc.201600062

Cited by 22 publications

(3 citation statements)

References 77 publications

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“…2), which enhances the nucleophilicity of the counteranions. [42][43][44][45][46][47][48][49][50][51][52][53][54][55] For example, Shigeno, Korenaga, and Kondo recently reported that P 4 -tBu activates an alkanethiol (pK a of n-BuSH: 17.0 in DMSO). 56 In this study, highly basic phosphazene bases P 4 -tBu and P 2 -tBu (pK BH+ of P 2 -Et: 21.15 in DMSO) exhibited good catalytic activity in comparison with weaker bases such as DBU (pK BH+ 13.9 in DMSO) and P 1 -tBu-TP (pK BH+ 17.4 ± 1.2 in DMSO) (Table 1, Entries 5-8).…”

Section: Resultsmentioning

confidence: 99%

Catalytic thiolation-depolymerization of oxyphenylene type super engineering plastics via selective carbon-oxygen main chain cleavages

Minami,

Imamura,

Matsuyama

et al. 2023

Preprint

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As the effective use of carbon resources has become a pressing societal issue, the importance of chemical recycling of plastics has increased. The catalytic depolymerization method for plastics is a promising approach for creating valuable products under efficient and mild conditions. Although depolymerization methods for various commodity plastics and several engineering plastics have been developed, the degradation of robust super engineering plastics that have very high heat resistance, chemical resistance, and low solubility is nearly unexplored. Herein, we report the catalytic depolymerization of oxyphenylene-based super engineering plastics such as polyetheretherketone, polysulfone, and polyetherimide using thiols via selective carbon–oxygen main chain cleavage to form monomer-type molecules, electron-deficient arenes with sulfur functional groups and bisphenols. The catalyst combination of a bulky phosphazene base P4-tBu with inorganic bases such as tripotassium phosphate or cesium carbonate enabled smooth depolymerization by activating the thiols to form reactive thiolates. This depolymerization method could be utilized with carbon- or glass fiber-enforced polyetheretherketone materials and a consumer resin. The sulfur functional groups in one product could be transformed to amino and sulfonium groups and fluorine by using suitable catalysts. Notably these fluorinated products are the monomers of the parent super engineering plastics.

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Section: Resultsmentioning

confidence: 99%

Catalytic thiolation-depolymerization of oxyphenylene type super engineering plastics via selective carbon-oxygen main chain cleavages

Minami,

Imamura,

Matsuyama

et al. 2023

Preprint

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“…Subsequently, the same group used [Mg(HMDS) 2 ] with NHOs to synergistically activate the monomer, resulting in a significantly enhanced polymerization rate . Phosphazene catalysts, including phosphazene superbases (PBs) and phosphazenium salts, are extensively explored in the ROP of various monomers due to their high basicity, non-nucleophilic characteristics, and excellent solubility in solvents. − However, the ROP of PO catalyzed by commercially available PBs, such as using t -BuP 2 or t -BuP 1 as catalysts, has been hindered by their insufficient basicity. In contrast, the use of a more basic t -BuP 4 , despite the high efficiency in PO polymerization, often leads to chain transfers to PO.…”

Section: Introductionmentioning

confidence: 99%

Controlled Ring-Opening Polymerization of Epoxides Catalyzed by Metal-Free Phosphazenium Salts (P₅⁺): Using Carboxylic Acid as an Initiator to Prepare Esterified Polyethers

Liu,

Jiang,

Ren

et al. 2023

ACS Appl. Polym. Mater.

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The applications of functional polyether materials include surfactants, lubricants, pharmaceuticals, and fundamental components in polyurethane products. The ring-opening polymerization (ROP) using carboxylic acid as an initiator offers enhanced pathways for synthesizing α,ω-heterobifunctional polyethers with cleavable or modifiable α-end junctions. The primary challenge lies in achieving a compatible balance between high efficiency and precise control over polymerization, as the ester groups generated during initiation steps may not tolerate highly basic catalysts. Herein, we present metal-free phosphazenium salts, namely, tetrakis [tris(dimethylamino) phosphoranylidenamino] phosphonium carboxylates (P 5 + RCOO − ), as catalysts for the carboxylic acid-initiated ROP of epoxides. Promoted by the appropriate basicity of P 5 + RCOO − and electrostatic effects of loose cation−anion pairs, the P 5 + RCOO − catalysts display high efficiency and controlled/living behavior even with a low catalyst loading. Moreover, the catalysts can be easily scaled up to the kilogram scale through simple procedures. Our strategy has successfully provided well-defined α-(carboxylic ester)-ω-hydroxy polyethers (PPO, PEO, and PBO) with controlled molecular weight, low dispersity, and high end-group fidelity. The effectiveness of the catalyst system is supported by kinetic investigations, 1 H NMR and size exclusion chromatography (SEC) spectra, and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF-MS) analysis. This study provides a facile approach for synthesizing α,ω-heterobifunctional polyethers that have the potential for imparting degradability and amphiphilicity properties to polyether-based materials.

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“…In some recent theoretical studies, it was shown that in mixed CPI/guanidine systems where multiple intramolecular H-bonds (IMHB) stabilize conjugate acid PA values of up to 306.0 kcal mol –1 could be achieved. , Recently, we have demonstrated that troponimines (TI) possess the same capability as CPI, but resulting in higher GB/PA values . It should be mentioned that NOS design was not limited to theoretical investigations only; however, many theoretically designed NOS have been synthesized and are nowadays being used as promotors of chemical reactions. − Aromatization, therefore, is considered to be the main driving force in high-basicity trait of new NOS systems. Investigation on the possible role of the antiaromaticity character of some NOS candidates, however, still remained on the margin of NOS researchers’ desk, and the current paper tries to shed light on this area.…”

Section: Introductionmentioning

confidence: 99%

Step Forward to Stronger Neutral Organic Superbases: Fused Troponimines

2020

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In this study, using a computational approach, we are pursuing to find a proper answer about the possible application of fused TIs as superbases through the calculation and discussion of standard thermochemistry parameters, like gas-phase basicity (GB) and proton affinity (PA). In some studied cases, the role of aromaticity/antiaromaticity fluctuations supposed to be more important than mesomeric effects. In this sense, nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) were utilized in this study to probe into the aromaticity-related parameters of the proposed molecules. Results revealed the highest GB/PA values for the molecules having cyclobutadiene in between two troponimines. Additional investigation was performed into the other candidates of cyclobutadiene-fused troponimines by substituting several electron donors along with the changing position of donors. Some novel superbases offered record-holding GB/PA values so that PA magnitudes higher than 300 kcal mol −1 are now feasible for nonphosphorous neutral organic superbases (NOS).

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Protonated Phosphazenes: Structures and Hydrogen‐Bonding Organocatalysts for Carbonyl Bond Activation

Cited by 22 publications

References 77 publications

Catalytic thiolation-depolymerization of oxyphenylene type super engineering plastics via selective carbon-oxygen main chain cleavages

Catalytic thiolation-depolymerization of oxyphenylene type super engineering plastics via selective carbon-oxygen main chain cleavages

Controlled Ring-Opening Polymerization of Epoxides Catalyzed by Metal-Free Phosphazenium Salts (P₅⁺): Using Carboxylic Acid as an Initiator to Prepare Esterified Polyethers

Step Forward to Stronger Neutral Organic Superbases: Fused Troponimines

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Protonated Phosphazenes: Structures and Hydrogen‐Bonding Organocatalysts for Carbonyl Bond Activation

Cited by 22 publications

References 77 publications

Catalytic thiolation-depolymerization of oxyphenylene type super engineering plastics via selective carbon-oxygen main chain cleavages

Catalytic thiolation-depolymerization of oxyphenylene type super engineering plastics via selective carbon-oxygen main chain cleavages

Controlled Ring-Opening Polymerization of Epoxides Catalyzed by Metal-Free Phosphazenium Salts (P5+): Using Carboxylic Acid as an Initiator to Prepare Esterified Polyethers

Step Forward to Stronger Neutral Organic Superbases: Fused Troponimines

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Controlled Ring-Opening Polymerization of Epoxides Catalyzed by Metal-Free Phosphazenium Salts (P₅⁺): Using Carboxylic Acid as an Initiator to Prepare Esterified Polyethers