2525-02-2Relevant academic research and scientific papers
The influence of the p-alkyl substituent on the isomerization of o- quinones to p-quinone methides: Potential bioactivation mechanism for catechols
Iverson,Li Qing Hu,Vukomanovic,Bolton
, p. 537 - 544 (1995)
Previously, we have shown that an additional bioactivation pathway for the hepatocarcinogen safrole (1-allyl-3,4-(methylenedioxy)benzene) exists which may contribute to its toxic effects: initial O-dealkylation of the methylenedioxy ring, forming the catechol, hydroxychavicol (HC, 1-allyl-3,4- dihydroxybenzene), 2-electron oxidation to the o-quinone (4-allyl-3,5- cyclohexadien-1,2-dione), and isomerization, forming the more electrophilic p-quinone methide (2-hydroxy-4-allylidene-2,5-cyclohexadien-1-one) [Bolton, J. L., Acay, N. M., and Vukomanovic, V. (1994) Chem. Res. Toxicol. 7, 443- 450]. In the present investigation, we explored the effects of changing π- conjugation at the 4-position on both the rate of isomerization of the initially formed o-quinones to the QMs and the reactivity of the quinoids formed from 4-propylcatechol (1), 2,3-dihydroxy-5,6,7,8-tetrahydronaphthalene (2), and 4-cinnamylcatechol (3). We selectively oxidized the catechols to the corresponding o-quinones or p-quinone methides and trapped these reactive electrophiles with glutathione (GSH). The GSH adducts were fully characterized by UV, NMR, and mass spectrometry. Microsomal incubations with the parent catechols in the presence of glutathione produced only o-quinone glutathione conjugates. However, if the trapping agent (GSH) was added after an initial incubation time, both o-quinone and p-quinone methide GSH conjugates were observed. The results indicate that extended π-conjugation at the para position enhances the rate of isomerization of the o-quinone to the quinone methide. Thus the half-life of the o-quinones decreased in the following order: the o-quinone of 1 > 2 > HC > 3. In support of this, AM1 semiempirical calculations also showed the same trend: an increase in stability of the quinone methide relative to the o-quinone with extending π- conjugation at the 4-position. Finally, kinetic studies showed that the reactivity of the quinone methides with water increases with decreasing π- conjugation. These data provide further evidence that formation of these electrophilic quinone methides from o-quinones may be a general bioactivation pathway for synthetic and naturally occurring 4-alkylcatechols.
Renewable Thermoplastics Based on Lignin-Derived Polyphenols
Zhao, Shou,Abu-Omar, Mahdi M.
, p. 3573 - 3581 (2017)
A series of renewable triphenylmethane-type polyphenols (TPs) were synthesized from lignin-derived guaiacols (methylguaiacol and propylguaiacol) and aldehydes (4-hydroxybenzaldehyde, vanillin, and syringaldehyde). By converting guaiacols to catechols through ortho-demethylation, the newly formed phenolic para site remarkably improved the reactivity as reflected by conversion of TPs. Optimized reagent molar ratios were aldehyde/catechol (1:4) and aldehyde/H2SO4 (1:3). A typical TP (VAN-M-CAT) was converted to glycidyl ether (GE-VAN-M-CAT) to examine its feasibility as precursor to epoxy thermosets. The resulting network exhibited excellent glassy modulus (12.3 GPa), glass transition temperature (167 °C), and thermal stability, which were attributed to the rigid triphenylmethane framework, high functionality (n = 5), and high cross-link density. A fully biobased epoxy comonomer (VAN-LIN-EPO), which was prepared by esterification of VAN-M-CAT with linoleic acid followed by epoxidation, could tune the material properties. This study widens the synthesis route of fully biobased polyphenols, which can yield polymers with excellent properties.
Efficient demethylation of aromatic methyl ethers with HCl in water
Bomon, Jeroen,Bal, Mathias,Achar, Tapas Kumar,Sergeyev, Sergey,Wu, Xian,Wambacq, Ben,Lemière, Filip,Sels, Bert F.,Maes, Bert U. W.
supporting information, p. 1995 - 2009 (2021/03/26)
A green, efficient and cheap demethylation reaction of aromatic methyl ethers with mineral acid (HCl or H2SO4) as a catalyst in high temperature pressurized water provided the corresponding aromatic alcohols (phenols, catechols, pyrogallols) in high yield. 4-Propylguaiacol was chosen as a model, given the various applications of the 4-propylcatechol reaction product. This demethylation reaction could be easily scaled and biorenewable 4-propylguaiacol from wood and clove oil could also be applied as a feedstock. Greenness of the developed methodversusstate-of-the-art demethylation reactions was assessed by performing a quantitative and qualitative Green Metrics analysis. Versatility of the method was shown on a variety of aromatic methyl ethers containing (biorenewable) substrates, yielding up to 99% of the corresponding aromatic alcohols, in most cases just requiring simple extraction as work-up.
Structure–Activity Relationship of Anti-malarial Allylpyrocatechol Isolated from Piper betle
Horii, Toshihiro,Itagaki, Sawako,Kawano, Tomikazu,Miyoshi, Akihito,Murakami, Nobutoshi,Tamura, Satoru
, p. 784 - 790 (2020/09/18)
Malaria disease remains a serious worldwide health problem. In South-East Asia, one of the malaria infection “hot-spots,” medicinal plants such as Piper betle have traditionally been used for the treatment of malaria, and allylpyrocatechol (1), a constituent of P. betle, has been shown to exhibit anti-malarial activities. In this study, we verified that 1 showed in vivo anti-malarial activity through not only intraperitoneal (i.p.) but also peroral (p.o.) administration. Additionally, some analogs of 1 were synthesized and the structure–activity relationship was analyzed to disclose the crucial sub-structures for the potent activity.
Br?nsted Acid Catalyzed Tandem Defunctionalization of Biorenewable Ferulic acid and Derivates into Bio-Catechol
Bal, Mathias,Bomon, Jeroen,Liao, Yuhe,Maes, Bert U. W.,Sels, Bert F.,Sergeyev, Sergey,Van Den Broeck, Elias,Van Speybroeck, Veronique
supporting information, p. 3063 - 3068 (2020/02/05)
An efficient conversion of biorenewable ferulic acid into bio-catechol has been developed. The transformation comprises two consecutive defunctionalizations of the substrate, that is, C?O (demethylation) and C?C (de-2-carboxyvinylation) bond cleavage, occurring in one step. The process only requires heating of ferulic acid with HCl (or H2SO4) as catalyst in pressurized hot water (250 °C, 50 bar N2). The versatility is shown on a variety of other (biorenewable) substrates yielding up to 84 % di- (catechol, resorcinol, hydroquinone) and trihydroxybenzenes (pyrogallol, hydroxyquinol), in most cases just requiring simple extraction as work-up.
Anchimerically Assisted Selective Cleavage of Acid-Labile Aryl Alkyl Ethers by Aluminum Triiodide and N, N-Dimethylformamide Dimethyl Acetal
Sang, Dayong,Yue, Huaxin,Zhao, Zhengdong,Yang, Pengtao,Tian, Juan
, p. 6429 - 6440 (2020/07/14)
Aluminum triiodide is harnessed by N,N-dimethylformamide dimethyl acetal (DMF-DMA) for the selective cleavage of ethers via neighboring group participation. Various acid-labile functional groups, including carboxylate, allyl, tert-butyldimethylsilyl (TBS), and tert-butoxycarbonyl (Boc), suffer the conditions intact. The method offers an efficient approach to cleaving catechol monoalkyl ethers and to uncovering phenols from acetal-type protecting groups such as methoxymethyl (MOM), methoxyethoxymethyl (MEM), and tetrahydropyranyl (THP) chemoselectively.
Selective ether bond breaking method of aryl alkyl ether
-
Paragraph 0119-0123, (2020/09/16)
The invention discloses a selective aryl alkyl ether cracking method, which comprises that aryl alkyl ether, aluminum iodide and an additive are subjected to a selective ether bond cleavage reaction in an organic solvent at a temperature of -20 DEG C to a reflux temperature to generate phenol and derivatives thereof. The method is mild in condition and simple and convenient to operate, is suitablefor cracking aryl alkyl ether containing o-hydroxyl and o-carbonyl and acetal ether, and can also be used for removing tertiary carbon hydroxyl protecting groups with higher steric hindrance, such astriphenylmethyl, tertiary butyl and the like.
One-pot hydrodeoxygenation (HDO) of lignin monomers to C9 hydrocarbons co-catalysed by Ru/C and Nb2O5
Abu-Omar, Mahdi M.,Ford, Peter C.,Li, Simin,Liu, Baoyuan,Luo, Zhongyang,Truong, Julianne
supporting information, p. 7406 - 7416 (2020/11/25)
A physical mixture of Ru/C and Nb2O5 is an effective catalyst for upgrading lignin monomers under low H2 pressure at 250 °C to a clean cut of hydrocarbon liquid fuels. The reaction solvent is water with a small amount of methanol additive. Hydrodeoxygenation (HDO) was evaluated using dihydroeugenol (DHE) as an exemplary lignin monomer model. Under optimized conditions, 100% conversion of DHE and very high selectivity to propyl cyclohexane (C9 hydrocarbon) was achieved. Nb2O5 was prepared at a low temperature (450 °C) and was shown to contain acid sites that enhance the production of fully deoxygenated products. The methanol additive serves as a hydrogen source for the Ru/C catalysed reduction of the aromatic ring. In addition, when a substrate mixture of DHE, isoeugenol and 4-allylsyringol simulating lignin products was employed, 100% conversion to propyl cyclohexane (76%) and propyl benzene (24%) was observed, thereby suggesting the general applicability of this catalyst system for funneling lignin monomers into a clean cut of hydrocarbon liquid fuels. This study sheds light on the function of each catalyst component and provides a simple and green utilization of biomass monomers as a feedstock for renewable hydrocarbon fuels. This journal is
Low-Temperature Catalytic Hydrogenolysis of Guaiacol to Phenol over Al-Doped SBA-15 Supported Ni Catalysts
Wang, Qiuyue,Chen, Yufang,Yang, Guanheng,Deng, Ping,Lu, Xinqing,Ma, Rui,Fu, Yanghe,Zhu, Weidong
, p. 4930 - 4938 (2020/08/26)
Selective hydrogenolysis of aromatic carbon-oxygen (Caryl?O) bonds is a key strategy for the generation of aromatic chemicals from lignin. However, this process is usually operated at high temperatures and pressures over hydrogenation catalysts, resulting in a low selectivity for aromatics and an extra consumption of hydrogen. Here, a series of Al-doped SBA-15 mesoporous materials with different Si/Al molar ratios (Al-SBA-15) were prepared via a post-synthesis method using NaAlO2 as the Al source, and then Al-SBA-15 supported Ni catalysts (Ni/Al-SBA-15) were prepared by a deposition-precipitation method using urea as the hydrolysis reagent. The prepared supports and catalysts were extensively characterized using various techniques such as XRD, N2 adsorption/desorption, TEM, 27Al NMR, NH3-TPD, XPS, H2-TPR, and pyridine-FT-IR, and the catalysts were evaluated in the hydrogenolysis of the Caryl?O bond in guaiacol and lignin derived compounds under mild conditions. The effects of the Si/Al ratio in catalyst and reaction parameters on guaiacol conversion and product distribution were investigated in detail, associated with solvent effect. The incorporation of Al into the framework of SBA-15 can improve the Lewis acidity and the dispersion of the supported Ni particles and yet modulate the metal-support interactions, which are propitious to the hydrogenolysis of the Caryl?O bond in guaiacol. The catalyst Ni/Al-SBA-15 with a Si/Al molar ratio of 10 shows the best performance with a guaiacol conversion of 87.4 % and a phenol selectivity of 76.9 % under the mild conditions conducted, because of its proper acidity, suitable metal-support interactions, and high dispersion of the active species. The present study would stimulate research and development in multi-functional catalysts for the generation of valuable chemicals from biomass.
METHOD FOR THE DEACYLATION AND/OR DEALKYLATION OF COMPOUNDS
-
Page/Page column 23; 37, (2019/02/15)
The present invention in general relates to a method for the deacylation and/or dealkylation (both O-dealkylation as well as C-dealkylation) of compounds, more specifically of aromatic compounds. The method is characterized by contacting the compound with an acid-containing aqueous reaction mixture using high temperature and high pressure conditions. The invention also provides a method for preparing a compound suitable for further deacylation using the method of the invention.
