Organic superbase<i>t</i>-Bu-P4-catalyzed demethylations of methoxyarenes

Shigeno, Masanori; Hayashi, Kazutoshi; Korenaga, Takashi; Nozawa‐Kumada, Kanako; Kondo, Yoshinori

doi:10.1039/d2qo00483f

Cited by 12 publications

(4 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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

View full text Add to dashboard Cite

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.

show abstract

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

View full text Add to dashboard Cite

show abstract

“…We also investigated the impact of solvation using solvents known to favour this type of reaction: NMP [15][16][17][18]20,21 , THF 23 and toluene 12 . The solvent polarity turned out to be important, as almost no reaction occurred in THF and toluene (see Supplementary material).…”

Section: Synlett Lettermentioning

confidence: 99%

“…Thiolate salts offer an interesting alternative to Lewis acid as demethylation reagents. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Thiolate-mediated demethylation reactions proceed through a nucleophilic substitution mechanism. 9 Koutek demonstrated that the reactivity of an aryl methoxy group towards NaSEt is highly dependent on electronic factors; i.e., the nature and the relative position of the other substituents on the aryl ring.…”

mentioning

confidence: 99%

Chemo- and Regioselective Demethylation of 2-Bromo-α-resorcylic Acid Derivatives Using Alkylthiolate Salts

Voyer,

Cardinal,

Fraser

et al. 2024

Synlett

View full text Add to dashboard Cite

We report here the chemo- and regioselective demethylation of 3,5-dimethoxy-2-bromo-α-resorcylic acid esters by a thiolate nucleophilic displacement reaction. Optimized conditions facilitate yields up to 93% for o-bromo selective demethylation of diverse ester derivatives of dimethoxy 2-bromo-α-resorcylic acid. Our results highlight a new, efficient, and reliable demethylation reagent, as well as a useful steric bias directing strategy.

show abstract

“…Superbases were extensively used for catalyzing organic synthesis − and CO 2 capture, − but only a few attempts have been tried on the application of superbases in the CHC of lignin-related model compounds (LRMCs) − and heavy carbon resources. − Since the C-O bridged bonds (COBBs), such as ARCH 2 O-CH 2 AR, AROCH 2 AR, and ARO-AR, are the predominant COBBs in lignites, − insight into the CHCs of LRMCs, such as oxybis(methylene)dibenzene, ,, benzyloxybenzene, , and oxidibenzene , with COBBs, has become a powerful tool to understand the mechanisms for selectively cleaving COBBs and hydrogenating AR in lignites at molecular level. Among the COBBs, BRO-BR bond (360 kJ mol –1 ) in oxidibenzene is the strongest, , so the research gaining insight into the cleavage of COBB in oxidibenzene has attracted extensive attention.…”

Section: The Roles Of H– and H···h In The Chc Of Heavy Carbon Resourcesmentioning

confidence: 99%

Advances in Catalytic Hydroconversion of Typical Heavy Carbon Resources under Mild Conditions

Wei

Bai

et al. 2023

Energy Fuels

View full text Add to dashboard Cite

Low-rank coals, biomass, and heavy petroleum are typical heavy carbon resources, which are currently not efficiently used, and many processes for the current use of the heavy carbon resources cause severe environmental pollution with very limited economic benefits even with a great deficit. Efficiently using the heavy carbon resources can greatly improve the environment and create huge economic benefits. The main difficulty in efficiently using the heavy carbon resources is the high content of aromatic rings (ARs) and heteroatoms in addition to the insoluble and complex macromolecular structures of the heavy carbon resources. Catalytic hydroconversion (CHC) includes catalytic hydrocracking and subsequent catalytic hydrofining. Many low-rank coals consist of macromolecular species, which are rich in bridged linkages connecting structural units, especially ARs, on which side chains are usually contained. Many ARs, bridged linkages, and side chains contain heteroatoms. Over a proper active catalyst, many bridged linkages and even some side chains can be cleaved, and many heteroatoms outside the ARs can be removed by the CHC under mild conditions to get soluble portions with relatively simple composition, facilitating subsequent separation to obtain pure chemicals, especially value-added products, such as condensed aromatics. The remaining economically inseparable species can be converted to liquid chemicals, especially nonsubstituted and alkyl-substituted cyclanes, by subsequent catalytic hydrofining. Catalysts and catalytically formed active hydrogen play crucial roles in the processes. Mainly based on our investigations, the related advances are reviewed in this work.

show abstract

Organic superbaset-Bu-P4-catalyzed demethylations of methoxyarenes

Abstract: Herein, we report that the organic superbase t-Bu-P4 catalyzes the demethylation reactions of methoxyarenes in the presence of alkanethiol and hexamethyldisilazane. The system can efficiently convert a variety of substrates,...

Cited by 12 publications

References 65 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

Chemo- and Regioselective Demethylation of 2-Bromo-α-resorcylic Acid Derivatives Using Alkylthiolate Salts

Advances in Catalytic Hydroconversion of Typical Heavy Carbon Resources under Mild Conditions

Contact Info

Product

Resources

About