- Renewable thermosetting resins and thermoplastics from vanillin
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Two cyanate ester resins and a polycarbonate thermoplastic have been synthesized from vanillin. The bisphenol precursors were prepared by both an electrochemical route as well as by a McMurry coupling reaction. 1,2-Bis(4-cyanato-3-methoxyphenyl)ethene (6) had a high melting point of 237 °C and did not cure completely under a standard cure protocol. In contrast, the reduced version, 1,2-bis(4-cyanato-3-methoxyphenyl)ethane (7) melted at 190 °C and underwent complete cure to form a thermoset material with Tg = 202 °C. 7 showed thermal stability up to 335 °C and decomposed via formation of phenolics and isocyanic acid. A polycarbonate was then synthesized from the reduced bisphenol by a transesterification reaction with diphenylcarbonate. The polymer had Mn = 3588, Mw/Mn = 1.9, and a Tg of 86 °C. TGA/FTIR data suggested that the polycarbonate decomposed via formation of benzodioxolones with concomitant elimination of methane. The results show that vanillin is a useful precursor to both thermosetting resins and thermoplastics without significant modification. This journal is
- Harvey, Benjamin G.,Guenthner, Andrew J.,Meylemans, Heather A.,Haines, Shannon R. L.,Lamison, Kevin R.,Groshens, Thomas J.,Cambrea, Lee R.,Davis, Matthew C.,Lai, William W.
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- Molybdenum-Catalyzed Deoxygenation Coupling of Lignin-Derived Alcohols for Functionalized Bibenzyl Chemicals
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With the growing demand for sustainability and reducing CO2 footprint, lignocellulosic biomass has attracted much attention as a renewable, carbon-neutral and low-cost feedstock for the production of chemicals and fuels. To realize efficient utilization of biomass resource, it is essential to selectively alter the high degree of oxygen functionality of biomass-derivates. Herein, we introduced a novel procedure to transform renewable lignin-derived alcohols to various functionalized bibenzyl chemicals. This strategy relied on a short deoxygenation coupling pathway with economical molybdenum catalyst. A well-designed H-donor experiment was performed to investigate the mechanism of this Mo-catalyzed process. It was proven that benzyl carbon-radical was the most possible intermediate to form the bibenzyl products. It was also discovered that the para methoxy and phenolic hydroxyl groups could stabilize the corresponding radical intermediates and then facilitate to selectively obtain bibenzyl products. Our research provides a promising application to produce functionalized aromatics from biomass-derived materials.
- Jiang, Huifang,Lu, Rui,Luo, Xiaolin,Si, Xiaoqin,Xu, Jie,Lu, Fang
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supporting information
p. 1292 - 1296
(2020/12/09)
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- Method for preparation of bibenzyl compounds by photocatalytic one-step process
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The invention relates to a brand new low-cost method for synthesis of bibenzyl compounds. The method adopts green and clean light energy as the reaction energy, and takes toluene or a toluene derivative as the raw material to prepare bibenzyl compounds under the catalysis of a solid photocatalyst. The method is carried out at room temperature, and can prepare bibenzyl compounds directly by illumination. The reaction process includes: mixing a toluene derivative, a catalyst and a solvent, then putting the mixture into a pressure-resistant quartz container (larger than 1MPa), and performing replacement with inert gas, conducting illumination stirring at room temperature, and carrying out reaction for 1 or more hour. At the end of the reaction, the catalyst can be easily separated from the reaction system and can be recycled repeatedly, the reaction product can be separated by crystallization, and the yield of bibenzyl compounds can reach 3.21g (g catalyst)h. The method can be used for direct preparation of 1, 2-diphenylethane and natural bibenzyl drugs.
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Paragraph 0063
(2019/07/04)
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- Synthesis of potential bisphenol A substitutes by isomerising metathesis of renewable raw materials
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Isomerising metathesis is introduced as a sustainable method to produce dihydroxystilbene derivatives from eugenol, a clove oil ingredient, and cardanol from cashew nut shell liquid. Hydrogenation of the dihydroxystilbenes provided their di(hydroxyphenyl)ethane analogues. Initial studies to convert these monomers into polycarbonates and thiol-ene polymers support their potential to replace the petrol-derived bisphenol A (BPA). The estrogenic activity of the monomers derived from cardanol was found to be in the same range as that of BPA, a known endocrine disruptor. In contrast, eugenol-derived materials were found to be non-estrogenic, opening up new perspectives for bio-based food packaging materials.
- Trita,Over,Pollini,Baader,Riegsinger,Meier,Goo?en
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supporting information
p. 3051 - 3060
(2017/07/15)
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- Structural characterization of lignin isolated from coconut (Cocos nucifera) coir fibers
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The structure of the isolated milled wood lignin from coconut coir has been characterized using different analytical methods, including Py-GC/MS, 2D NMR, DFRC, and thioacidolysis. The analyses demonstrated that it is a p-hydroxyphenyl-guaiacyl-syringyl (H-G-S) lignin, with a predominance of G units (S/G ratio 0.23) and considerable amounts of associated p-hydroxybenzoates. Two-dimensional NMR indicated that the main substructures present in this lignin include β-O-4′ alkyl aryl ethers followed by phenylcoumarans and resinols. Two-dimensional NMR spectra also indicated that coir lignin is partially acylated at the γ-carbon of the side chain with p-hydroxybenzoates and acetates. DFRC analysis showed that acetates preferentially acylate the γ-OH in S rather than in G units. Despite coir lignin's being highly enriched in G-units, thioacidolysis indicated that β-β′ resinol structures are mostly derived from sinapyl alcohol. Finally, we find evidence that the flavone tricin is incorporated into the coconut coir lignin, as has been recently noted for various grasses.
- Rencoret, Jorge,Ralph, John,Marques, Gisela,Gutiérrez, Ana,Martínez, ángel T.,Del Río, José C.
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p. 2434 - 2445
(2013/05/09)
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- Low-valent titanium mediated synthesis of hydroxystilbenoids: Some new observations
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A series of phenolic stilbenoids possessing different numbers and positions of hydroxylation, partial methoxyl substituents and nature of olefinic moieties has been synthesized by McMurry coupling. It is found that the McMurry coupling of the phenolic aldehydes furnishes the dihydrostilbenes via an in situ hydrogenation, while the phenolic ketones give the stilbenes. Interestingly, the study also reveals that the low-valent titanium reagent (TiCl 3-Zn-THF) could selectively depyranylate phenolic -OTHP function without affecting alcoholic -OTHP group.
- Shadakshari,Rele,Nayak,Chattopadhyay
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p. 1934 - 1938
(2007/10/03)
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