- Study on in Vitro Preparation and Taste Properties of N-Ethyl-2-Pyrrolidinone-Substituted Flavan-3-Ols
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N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs) were prepared by an in vitro model reaction, and the taste thresholds of EPSFs and their dose-over-threshold factors in large-leaf yellow tea (LYT) were investigated. The effects of initial reactant
- Han, Zisheng,Ho, Chi-Tang,Jiang, Zongde,Lai, Guoping,Qin, Chunyin,Wan, Xiaochun,Wen, Mingchun,Zhai, Xiaoting,Zhang, Hui,Zhang, Liang
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- Photocatalytic Degradation of 4,4′-Isopropylidenebis(2,6-dibromophenol) on Magnetite Catalysts vs. Ozonolysis Method: Process Efficiency and Toxicity Assessment of Disinfection By-Products
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Flame retardants have attracted growing environmental concern. Recently, an increasing number of studies have been conducted worldwide to investigate flame-retardant sources, environmental distribution, living organisms’ exposure, and toxicity. The presented studies include the degradation of 4,4′-isopropylidenebis(2,6-dibromophenol) (TBBPA) by ozonolysis and photocatalysis. In the photocatalytic process, nano-and micro-magnetite (n-Fe3 O4 and μ-Fe3 O4) are used as a catalyst. Monitoring of TBBPA decay in the photocatalysis and ozonolysis showed photocatalysis to be more effective. Significant removal of TBBPA was achieved within 10 min in photocatalysis (ca. 90%), while for ozonation, a comparable effect was observed within 70 min. To determine the best method of TBBPA degradation concentration on COD and TOC, the removals were examined. The highest oxidation state was obtained for photocatalysis on μ-Fe3 O4, whereas for n-Fe3 O4 and ozonolysis, the COD/TOC ratio was lower. Acute toxicity results show noticeable differences in the toxicity of TBBPA and its degradation products to Artemia franciscana and Thamnocephalus platyurus. The EC50 values indicate that TBBPA degradation products were toxic to harmful, whereas the TBPPA and post-reaction mixtures were toxic to the invertebrate species tested. The best efficiency in the removal and degradation of TBBPA was in the photocatalysis process on μ-Fe3 O4 (reaction system 1). The examined crustaceans can be used as a sensitive test for acute toxicity evaluation.
- Balawejder, Maciej,Barylyak, Adriana,Bobitski, Yaroslav,Kisa?a, Joanna,Tomaszewska, Anna
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- Method for promoting iron-catalyzed oxidation of aromatic compound carbon - hydrogen bond to synthesize phenol by ligand
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The method comprises the following steps: iron is used as - a catalyst metal; a sulfur-containing amino acid or cystine-derived dipeptide is a ligand; and under the common action of hydrogen peroxide as an oxidizing agent, an aromatic compound is synthesized to prepare a phenol. Under the action of an acid as an accelerant and hydrogen peroxide as an oxidizing agent, the aryl carbon - hydrogen bond is directly hydroxylated to form a phenolic compound, and the method for preparing the phenol by the catalytic oxidation reaction has a plurality of advantages. The reaction raw materials, the oxidant and the promoter are wide in source, low in price, environment-friendly and good in stability. The aromatic compound carbon - hydrogen bonds directly participate in the reaction to react in one step to form phenol. The reaction condition is mild, the functional group compatibility and the application range are wide. The reaction selectivity is good; under the optimized reaction conditions, the target product separation yield can reach 85%.
- -
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Paragraph 0106-0107; 0129
(2021/09/21)
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- Iron-catalyzed arene C-H hydroxylation
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The sustainable, undirected, and selective catalytic hydroxylation of arenes remains an ongoing research challenge because of the relative inertness of aryl carbon-hydrogen bonds, the higher reactivity of the phenolic products leading to over-oxidized by-products, and the frequently insufficient regioselectivity. We report that iron coordinated by a bioinspired L-cystine-derived ligand can catalyze undirected arene carbon-hydrogen hydroxylation with hydrogen peroxide as the terminal oxidant. The reaction is distinguished by its broad substrate scope, excellent selectivity, and good yields, and it showcases compatibility with oxidation-sensitive functional groups, such as alcohols, polyphenols, aldehydes, and even a boronic acid. This method is well suited for the synthesis of polyphenols through multiple carbon-hydrogen hydroxylations, as well as the late-stage functionalization of natural products and drug molecules.
- Cheng, Lu,Wang, Huihui,Cai, Hengrui,Zhang, Jie,Gong, Xu,Han, Wei
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- RETRACTED ARTICLE: Selective photocatalytic conversion of guaiacol using g-C3N4 metal free nanosheets photocatalyst to add-value products
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Valorization of lignin into high valuable chemical is a critical challenge. Its availability is a key factor for the development of viable lignocellulosic processes to replace fossil derived compounds. In this work, new insights on the high photocatalytic conversion of guaiacol (82%) as a lignin model compound was achieved, also, high selectivity to p-benzoquinone (59%), catechol (27%), and pyrogallol (6%) was obtained using metal-free pyrolyzed g-C3N4 under visible light irradiation. To highlight the new insights, experimental parameters were modified to control the reaction mechanism to increase selectivity and photo-conversion. g-C3N4 photocatalyst was synthesized through urea calcination at 550 °C and the photocatalytic performance was assessed in terms of pyrolysis time, where higher time resulted in better photocatalytic activity. This effect was attributed to smaller structures and therefore better quantum confinement of the charges. The oxidation was promoted by [rad]OH radicals, which were detected through EPR operando mode and the addition of radical scavengers. A reaction pathway was proposed, in which the ·OH attacks guaiacol through a methoxy group. The photocatalytic reaction can be tuned using external oxidant agents such as O2 and/or H2O2 to promote certain radical formation, enhancing conversion rates and promoting selectivity for a specific product, where yield shifting from p-benzoquinone to pyrogallol was experimentally observed.
- Rojas,Espinoza-Villalobos,Salazar,Escalona,Contreras,Melin,Laguna-Bercero,Sánchez-Arenillas,Vergara,Caceres-Jensen,Rodriguez-Becerra,Barrientos
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- Br?nsted Acid Catalyzed Tandem Defunctionalization of Biorenewable Ferulic acid and Derivates into Bio-Catechol
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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.
- Bal, Mathias,Bomon, Jeroen,Liao, Yuhe,Maes, Bert U. W.,Sels, Bert F.,Sergeyev, Sergey,Van Den Broeck, Elias,Van Speybroeck, Veronique
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p. 3063 - 3068
(2020/02/05)
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- Biocatalytic Methyl Ether Cleavage: Characterization of the Corrinoid-Dependent Methyl Transfer System from Desulfitobacterium hafniense
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The ether functionality represents a very common motif in organic chemistry and especially the methyl ether is commonly found in natural products. Its formation and cleavage can be achieved via countless chemical procedures. Nevertheless, since in particular the cleavage often involves harsh reaction conditions, milder alternatives are highly demanded. Very recently, we have reported on a biocatalytic shuttle catalysis concept for reversible cleavage and formation of phenolic O-methyl ethers employing a corrinoid-dependent methyl transferase system from the anaerobic organism Desulfitobacterium hafniense. Here we report the technical study of this system, focusing on the demethylation of guaiacol as model reaction. The optimal buffer-, pH-, temperature- and cofactor-preferences were determined as well as the influence of organic co-solvents. Beside methyl cobalamin also hydroxocobalamin turned out to be a suitable cofactor species, although the latter required activation. Various O-methyl phenyl ethers were successfully demethylated with conversions up to 82% at 10 mM substrate concentration. (Figure presented.).
- Richter, Nina,Farnberger, Judith E.,Pompei, Simona,Grimm, Christopher,Skibar, Wolfgang,Zepeck, Ferdinand,Kroutil, Wolfgang
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p. 2688 - 2695
(2019/03/28)
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- Enabling microbial syringol conversion through structure-guided protein engineering
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Microbial conversion of aromatic compounds is an emerging and promising strategy for valorization of the plant biopolymer lignin. A critical and often rate-limiting reaction in aromatic catabolism is O-aryl-demethylation of the abundant aromatic methoxy groups in lignin to form diols, which enables subsequent oxidative aromatic ring-opening. Recently, a cytochrome P450 system, GcoAB, was discovered to demethylate guaiacol (2-methoxyphenol), which can be produced from coniferyl alcohol-derived lignin, to form catechol. However, native GcoAB has minimal ability to demethylate syringol (2,6-dimethoxyphenol), the analogous compound that can be produced from sinapyl alcohol-derived lignin. Despite the abundance of sinapyl alcohol-based lignin in plants, no pathway for syringol catabolism has been reported to date. Here we used structure-guided protein engineering to enable microbial syringol utilization with GcoAB. Specifically, a phenylalanine residue (GcoA-F169) interferes with the binding of syringol in the active site, and on mutation to smaller amino acids, efficient syringol O-demethylation is achieved. Crystallography indicates that syringol adopts a productive binding pose in the variant, which molecular dynamics simulations trace to the elimination of steric clash between the highly flexible side chain of GcoA-F169 and the additional methoxy group of syringol. Finally, we demonstrate in vivo syringol turnover in Pseudomonas putida KT2440 with the GcoA-F169A variant. Taken together, our findings highlight the significant potential and plasticity of cytochrome P450 aromatic O-demethylases in the biological conversion of lignin-derived aromatic compounds.
- Machovina, Melodie M.,Mallinson, Sam J.B.,Knott, Brandon C.,Meyers, Alexander W.,Garcia-Borràs, Marc,Bu, Lintao,Gado, Japheth E.,Oliver, April,Schmidt, Graham P.,Hinchen, Daniel J.,Crowley, Michael F.,Johnson, Christopher W.,Neidle, Ellen L.,Payne, Christina M.,Houk, Kendall N.,Beckham, Gregg T.,McGeehan, John E.,DuBois, Jennifer L.
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p. 13970 - 13976
(2019/07/12)
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- Cleavage of Catechol Monoalkyl Ethers by Aluminum Triiodide-Dimethyl Sulfoxide
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Using eugenol and vanillin as model substrates, a practical method is developed for the cleavage o -hydroxyphenyl alkyl ethers. Aluminum oxide iodide (O=AlI), generated in situ from aluminum triiodide and dimethyl sulfoxide, is the reactive ether cleaving species. The method is applicable to catechol monoalkyl ethers as well as normal phenyl alkyl ethers for the removal of methyl, ethyl, isopropyl, and benzyl groups. A variety of functional groups such as alkenyl, allyl, amide, cyano, formyl, keto, nitro, and halogen are well tolerated under the optimum conditions. Partial hydrodebromination was observed during the demethylation of 4-bromoguaiacol, and was resolved using excess DMSO as an acid scavenger. This convenient and efficient procedure would be a practical tool for the preparation of catechols.
- Sang, Dayong,Tian, Juan,Tu, Xiaodong,He, Zhoujun,Yao, Ming
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p. 704 - 712
(2019/01/23)
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- METHOD FOR THE DEACYLATION AND/OR DEALKYLATION OF COMPOUNDS
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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.
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Page/Page column 23; 31
(2019/02/15)
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- Heterogeneous Nitrogen-doped Graphene Catalysed HOO? Generation via a Non-radical Mechanism for Base-free Dakin Reaction
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A heterogeneous nitrogen-doped graphene catalytic pathway for H2O2 activation to generate alkaline hydrogen peroxide (HOO?) through a non-radical mechanism was reported. Remarkably, the heterogeneous catalytic procedure has been used for the evergreen and environmentally Dakin reaction without using any transition metals, homogeneous bases, ligands, additives or promoters, completely. The study of catalyst structure and catalytic activities indicate that the most active sites are created by the graphitic N atoms at zig-zag edges of the sheets. In addition, N as dopant element changes the reactivity of the neighbour C atoms, and leads to the formation of carbon-hydroperoxide (C?(HOOH)) and C?O* (C?O?) transition state species on the graphene surface in catalytic the reaction. (Figure presented.).
- Sun, Wei,Gao, Lingfeng,Sun, Xu,Yang, Hua,Zheng, Gengxiu
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supporting information
p. 5210 - 5216
(2019/11/03)
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- Regioselective para-Carboxylation of Catechols with a Prenylated Flavin Dependent Decarboxylase
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The utilization of CO2 as a carbon source for organic synthesis meets the urgent demand for more sustainability in the production of chemicals. Herein, we report on the enzyme-catalyzed para-carboxylation of catechols, employing 3,4-dihydroxybenzoic acid decarboxylases (AroY) that belong to the UbiD enzyme family. Crystal structures and accompanying solution data confirmed that AroY utilizes the recently discovered prenylated FMN (prFMN) cofactor, and requires oxidative maturation to form the catalytically competent prFMNiminium species. This study reports on the in vitro reconstitution and activation of a prFMN-dependent enzyme that is capable of directly carboxylating aromatic catechol substrates under ambient conditions. A reaction mechanism for the reversible decarboxylation involving an intermediate with a single covalent bond between a quinoid adduct and cofactor is proposed, which is distinct from the mechanism of prFMN-associated 1,3-dipolar cycloadditions in related enzymes.
- Payer, Stefan E.,Marshall, Stephen A.,B?rland, Natalie,Sheng, Xiang,Reiter, Tamara,Dordic, Andela,Steinkellner, Georg,Wuensch, Christiane,Kaltwasser, Susann,Fisher, Karl,Rigby, Stephen E. J.,Macheroux, Peter,Vonck, Janet,Gruber, Karl,Faber, Kurt,Himo, Fahmi,Leys, David,Pavkov-Keller, Tea,Glueck, Silvia M.
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supporting information
p. 13893 - 13897
(2017/10/09)
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- CSJ acting as a versatile highly efficient greener resource for organic transformations
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Simple, new, greener and efficient alternatives to the existing protocols have been developed for the reduction of aromatic aldehydes to their corresponding alcohols, decarboxylation of substituted benzoic acids (C6-C1) and substituted cinnamic acids (C6-C3) with a hydroxyl group at the para position with respect to the acid group to corresponding phenolic compounds and vinyl phenols respectively by using a natural feedstock, cucumber juice (CSJ), which acts as a greener solvent system, performing a substrate-selective reaction. Additionally, the hydrolysis of the acetyl as well as the benzoyl group of aromatic compounds has been carried out to afford excellent yield by CSJ.
- Maity, Himadri Sekhar,Misra, Kaushik,Mahata, Tanushree,Nag, Ahindra
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p. 24446 - 24450
(2016/03/15)
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- Method for preparing pyrogallic acid through low-pressure catalysis
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The invention discloses a method for preparing pyrogallic acid through low-pressure catalysis. The method comprises the steps that water, tributylamine and pyrogallic acid are added into a reaction kettle, the temperature is increased to 80-90 DEG C, air is exhausted for 10-15 min, an air exhaust valve is turned off, the temperature is increased to 100-110 DEG C, the pressure is controlled to be 0.5-1.0 MPa, reaction is carried out for 2-3 h, and the temperature is decreased to room temperature; layering is carried out, an organic layer is washed with water 3-4 times and combined with a water layer in the step 1, ethyl acetate is used for extraction layering, the obtained ethyl acetate layer is combined, dichloromethane is added, cooling and crystallization are carried out, and pyrogallic acid solid is obtained. The process is easy to operate, the catalyst is easy to separate, the product yield is larger than or equal to 48%, the liquid phase purity is larger than or equal to 98.0%, the residue content is smaller than or equal to 0.1%, meanwhile, equipment requirements are low, and the method is suitable for industrial production.
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-
Paragraph 0014; 0015; 0016; 0017; 008; 0019
(2017/05/09)
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- Are of a kind of preparation are connected and method
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The invention belongs to the field of marine chemical industry medicine intermediates, and particularly relates to a method for preparing pyrogallol and phloroglucinol, wherein the preparation route that trimethoxybenzaldehyde is subjected to catalysis decarbonylation under a hydrogen atmosphere is adopted, the modified raney nickel is adopted as a catalyst to carry out a catalysis decarbonylation reaction in a solvent, the modified raney nickel is subjected to bulk phase and surface modification based on the conventional raney nickel preparation method, the modified component is one or a plurality of materials selected from Mn, Fe, Cr, Mo, Ti and W, and the modified component content (wt) is 0.5-10 wt%. The method has characteristics of environmental protection, easy operation, wide raw material source, short reaction step, simple catalyst preparation and capability of being repeatedly applied multiple times, and is suitable for industrialization.
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Paragraph 0031; 0033
(2017/02/24)
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- Study of the paracetamol degradation pathway that generates color and turbidity in oxidized wastewaters by photo-Fenton technology
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This study aims determining the effect that certain kind of water contaminants have on the changes of turbidity during their oxidation. Phenol is considered by its frequent presence in industrial discharges; meanwhile paracetamol is representative of emerging pollutants of pharmaceutical origin. Quite different results are observed in the turbidity changes during the oxidation of both pollutants that evolve following the kinetics of a reaction intermediate. The analysis of paracetamol and phenol degradation pathways reveals that operating conditions are important in the formation of intermediates that cause turbidity. The maximum turbidity levels are achieved operating at the ratios 12?mol HO? per 100?mg contaminant. However the turbidity generated during the paracetamol oxidation only reaches a third of the intensity achieved with phenol. During the paracetamol degradation, the intermediates causing turbidity are similar to the ones found during the phenol decomposition. These species are generated during the initial minutes of oxidation and possess structures of large size and molecular weight. At the máximum turbidity point, muconic acid and hydroquinone are identified and found to coexist with other compounds such as pyrogallol and resorcinol. Therefore, the path involving metasubstitution would be the main originator of turbidity. It is noteworthy the rapid formation of muconic acid that coexists with resorcinol-like species. These compounds enable the establishment of hydrogen bond interactions that yield supramolecular structures.
- Villota, Natalia,Lomas, Jose M.,Camarero, Luis M.
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p. 113 - 119
(2016/07/19)
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- H2O2 in WEB: a highly efficient catalyst system for the Dakin reaction
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Without using any transition metal catalyst, ligand, base, toxic or hazardous reagent, additives/promoters and organic solvent, green Dakin reactions have been successfully carried out by using H2O2 in a natural feedstock extract. The reaction proceeds in neat 'Water Extract of Banana' (WEB) at room temperature under aerobic conditions in very short reaction times and, therefore, it is an evergreen and environmentally sound alternative to the existing protocols for the Dakin reaction. In our system, the reaction was found to afford excellent yield for the desired product with different electron-withdrawing and electron-donating hydroxylated benzaldehydes.
- Saikia, Bishwajit,Borah, Parinita,Barua, Nabin Chandra
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supporting information
p. 4533 - 4536
(2015/09/15)
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- Biodegradation of aromatic hydrocarbons and phenols by bacteria isolated from caspian waters and soils
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Experimental studies have been carried out on the degradability of monoaromatic hydrocarbons (benzene, toluene, and ethylbenzene) and phenols (phenol, pyrocatechol, hydroquinone, tetrachloropyro- catechol) by bacteria isolated from coastal waters and soil
- Veliev,Salmanov,Babashly,Alieva,Bektashi
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p. 426 - 430
(2014/02/14)
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- Layered silicate as an excellent partner of a TiO2 photocatalyst for efficient and selective green fine-chemical synthesis
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When the partial oxidation of benzene to phenol, which is one of the most important reactions in chemical industry, was conducted using TiO2 in the presence of a phenol-philic adsorbent derived from a layered silicate, phenol was recovered in u
- Ide, Yusuke,Torii, Masato,Sano, Tsuneji
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p. 11784 - 11786
(2013/09/02)
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- New greener alternatives for bioreduction of aromatic aldehydes and decarboxylation of aromatic acids using juice of fruits
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Cocos nucifera L. and Borassus flabellifer L. juices act as bio catalytic system for the reduction of aromatic aldehydes to alcohols and selective decarboxylation of substituted cinnamic acid to styrene and substituted benzoic acid to polyphenolic compound. Both juices exhibit good activity when aromatic aldehydes and aromatic acids contain electron-donating groups at specific positions. Moreover, C. nucifera juice exhibits good result for the reduction and decarboxylation properties than B. flabellifer juice under the same reaction condition.
- Misra, Kaushik,Maity, Himadri Sekhar,Chanda, Subhankar,Nag, Ahindra
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experimental part
p. 92 - 95
(2012/09/22)
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- Preparation, characterization and use of 1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient, halogen-free and reusable ionic liquid catalyst for the trimethylsilyl protection of hydroxyl groups and deprotection of the obtained trimethylsilanes
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Novel 1,3-disulfonic acid imidazolium hydrogen sulfate, a halogen-free ionic liquid, is a recyclable and eco-benign catalyst for the trimethylsilyl protection of hydroxyl groups at room temperature under solvent free conditions to afford trimethylsilanes in excellent yields (92-100%) and in very short reaction times (1-5 min). Deprotection of the resulting trimethylsilanes can also be achieved using the same catalyst in methanol. The catalyst was characterized by IR, 1H NMR, 13C NMR and MS studies. All the products were extensively characterized by IR, 1H NMR, MS, and elemental and melting point analyses. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be recovered and reused for several times without loss of activity. The work-up of the reaction consists of a simple separation, followed by concentration of the crude product and purification.
- Shirini, Farhad,Khaligh, Nader Ghaffari,Akbari-Dadamahaleh, Somayeh
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- Ent-Eudesmane sesquiterpenoids, galloyl esters of the oak lactone precursor, and a 3-O-methylellagic acid glycoside from the wood of Platycarya strobilacea
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ent-Eudesmane sesquiterpenoids, 8,11-dihydroxy-2,4-cycloeudesmane, 11-hydroxy-2,4-cycloeudesman-8-one and 2,4-cyclo-7(11)-eudesmen-8-one, were isolated from the wood of Platycarya strobilacea, which has been used as an aromatic tree since at least the 18th century. On charring the wood, 2,4-cyclo-7(11)-eudesmen-8-one was detected in the smoke. In the charred wood, the concentrations of ellagitannins, such as galloyl pedunculagin, dramatically decreased, whereas concentrations of pentagalloyl glucose, and other gallotannins were relatively stable. In addition, two other compounds, the 6′-O-m- and p-digalloyl oak lactone precursor and the 3-O-methylellagic acid 4′-O-(4″-O-galloyl)-xylopyranoside, were isolated from the charred wood along with m- and p-digallic acid.
- Maeda, Hajime,Kakoki, Narumi,Ayabe, Mami,Koga, Yuki,Oribe, Tomoko,Matsuo, Yosuke,Tanaka, Takashi,Kouno, Isao
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experimental part
p. 796 - 803
(2011/11/06)
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- COUMESTAN-LIKE ANTIOXIDANTS AND UV ABSORBANTS
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The present invention relates to derivatives of the 1H-pyrano[4,3-b]benzofuran-1-one structure and their nitrogen analogues which possess powerful antioxidant properties combined with a highly effective UV absorbing functionality in one molecule. These compounds are especially useful in cosmetical and dermatological formulations.
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- One step hair coloring compositions using salts
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A hair coloring composition comprising the following two compositions which are mixed just prior to application to the hair: (a) a composition comprising a water-soluble peroxygen oxidizing agent; and (b) a composition comprising one or more oxidative hair coloring agents selected from the group consisting of an aromatic diamine, an amino phenol, a naphthol, a polyhydric phenol, a catechol and mixtures thereof; wherein the composition comprising one or more oxidative hair coloring agents further comprises al least one water soluble carbonate releasing salts; and optionally a water soluble ammonium salt, is described.
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- Synthesis of 1,2,3,4-tetrahydroxybenzenes from biomass-derived carbon
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A bioengineered synthesis scheme for the production of 1,2,3,4-tetrahydroxybenzene from a carbon source is provided. Methods of producing 1,2,3,4-tetrahydroxybenzene acid from a carbon source based on the synthesis scheme are also provided. Methods are also provided for converting 1,2,3,4-tetrahydroxybenzene to 1,2,3-trihydroxybenzene by catalytic hydrogenation.
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- Spectroscopy of hydrothermal reactions 23: The effect of OH substitution on the rates and mechanisms of decarboxylation of benzoic acid
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The decarboxylation rates of aqueous benzoic acid and 12 mono-, di-, and trihydroxy derivatives of benzoic acid were compared by using spectra from a flow reactor FTIR spectroscopy cell operating at 275 bar in the temperature range of 120-330 °C. Each compound was investigated at its natural pH and as the neutral acid (pH = 1.3-1.5). The decarboxylation reactions followed the first-order (or pseudo-first-order) rate law enabling the rate constants and corresponding Arrhenius parameters of the undissociated acids to be obtained. Based on the half-lives of the reactions at 200 °C, the thermal stability of the OH substituted benzoic acids follow the order: 2,4,6 > 2,4 > 2,3,4 > 2,6 > 2,5 > 2,3 > 3,4,5 > 2 > 3,4 > 4. Solutions of 3,5-dihydroxybenzoic and 3-hydroxybenzoic acids and unsubstituted benzoic acid had the highest thermal stability, whereas no decarboxylation was observed up to 330 °C at a residence time of about 45s. In general, the rate order is multiple ortho, para-OH substitution > ortho substitution > para substitution > meta substitution. The range of activation energies for the decarboxylation of OH substituted benzoic acids is 90-97 kJ/mol, and the rate differences are controlled mainly by activation entropy. The transition state structures were determined using density functional theory. Starting from the anti carboxylic hydrogen conformers in the gas phase, the activation energies to the transition state structures having the four-member C-C(O)-O-H ring are 213-260 kJ/mol using B3LYP/6-31G//B3LYP/6-31G and 202-246 kJ/mol using B3LYP/6-31+G(d,p)//B3LYP/6-31G(d). Incorporation of one water molecule forms a six-member cyclic structure, which dramatically reduces the activation energy by about 120-130 kJ/mol using B3LYP/6-31G//B3LYP/6-31G and by about 75 kJ/mol using B3LYP/6-31+G(d,p)//B3LYP/6-31G(d). In the water-catalyzed transition state structure, the water molecule acts as a bridge linked by two hydrogen bonds which enables concerted proton transfer and C-(CO2H) bond cleavage to occur. Although the calculated activation energy approximately follows the trend of the experimental half-lives, the experimental activation entropy appears to dominate in determining the rates.
- Li, Jun,Brill, Thomas B.
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p. 2667 - 2673
(2007/10/03)
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- Transition metal complexes as dye forming catalysts in hair coloring compositions
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A hair coloring composition comprising a first composition which comprises: (a) a dye forming transition metal salt or complex; which is first applied to the hair; and a second composition which comprises the following two compositions which are mixed just prior to application to the hair: (a) a composition comprising a water-soluble peroxygen oxidizing agent; and (b) a composition comprising one or more oxidative hair coloring agents selected from the group consisting of an aromatic diamine, an aminophenol, a polyhydric phenol a catechol and mixtures thereof.
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- Deoxygenation of polyhydroxybenzenes: An alternative strategy for the benzene-free synthesis of aromatic chemicals
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New synthetic connections have been established between glucose and aromatic chemicals such as pyrogallol, hydroquinone, and resorcinol. The centerpiece of this approach is the removal of one oxygen atom from 1,2,3,4-tetrahydroxybenzene, hydroxyhydroquinone, and phloroglucinol methyl ether to form pyrogallol, hydroquinone, and resorcinol, respectively. Deoxygenations are accomplished by Rh-catalyzed hydrogenation of the starting polyhydroxybenzenes followed by acid-catalyzed dehydration of putative dihydro intermediates. Pyrogallol synthesis consists of converting glucose into myo-inositol, oxidation to myo-2-inosose, dehydration to 1,2,3,4-tetrahydroxybenzene, and deoxygenation to form pyrogallol. Synthesis of pyrogallol via myo-2-inosose requires 4 enzyme-catalyzed and 2 chemical steps. For comparison, synthesis of pyrogallol from glucose via gallic acid intermediacy and the shikimate pathway requires at least 20 enzyme-catalyzed steps. A new benzene-free synthesis of hydroquinone employs conversion of glucose into 2-deoxy-scyllo-inosose, dehydration of this inosose to hydroxyhydroquinone, and subsequent deoxygenation to form hydroquinone. Synthesis of hydroquinone via 2-deoxy-scyllo-inosose requires 2 enzyme-catalyzed and 2 chemical steps. By contrast, synthesis of hydroquinone using the shikimate pathway and intermediacy of quinic acid requires 18 enzyme-catalyzed steps and 1 chemical step. Methylation of triacetic acid lactone, cyclization, and regioselective deoxygenation of phloroglucinol methyl ether affords resorcinol. Given the ability to synthesize triacetic acid lactone from glucose, this constitutes the first benzene-free route for the synthesis of resorcinol. Copyright
- Hansen, Chad A.,Frost
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p. 5926 - 5927
(2007/10/03)
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- 2,2-bis(3,5-disubstituted-4-hydroxyphenyl) propane derivative, process for production thereof, and process for producing pyrogallol using said derivative
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The present invention provides a 2,2-bis(3,5-disubstituted-4-hydroxyphenyl) propane derivative represented by general formula (1) STR1 wherein each R1 represents a hydrogen atom or a lower alkyl group; a process for producing such propane derivative; and a process for producing pyrogallol using such propane derivative. The compound of the present invention has by itself a periphyton-controlling activity required for the active ingredient used in a periphyton-controlling agent such as antifouling paint for ship's bottom, antifouling agent for fishing net, or the like. Further, by decomposing the above compound with an alkali or an acid, pyrogallol can be produced industrially without using any natural material.
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- Reaction of 3-dehydroshikimic acid with molecular oxygen and hydrogen peroxide: Products, mechanism, and associated antioxidant activity
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In the presence of molecular oxygen or hydrogen peroxide, inorganic phosphate catalyzes the conversion of 3-dehydroshikimic acid (DHS) into gallic acid. Other products formed in the reaction of DHS with oxygen include protocatechuic acid, tricarballylic acid, and pyrogallol. With hydrogen peroxide as oxidant, pyrogallol formation is not observed, and smaller amounts of tricarballylic acid are produced. Evidence favoring a mechanism involving phosphate-catalyzed tautomerization of DHS to a reactive enediol intermediate follows from the successful isolation of dihydrogallic acid when oxidant is excluded from phosphate-buffered solutions of DHS. The reductone-like solution chemistry of DHS and the radical quenching reactivity of the phenolics formed from DHS prompted an appraisal of DHS antioxidant activity. Based on two different analyses, DHS was discovered to possess significant antioxidant activity relative to α-tocopherol, gallic acid, propyl gallate, and tert-butylhydroquinone.
- Richman, Jack E.,Chang, Yu-Chen,Kambourakis, Spiros,Draths,Almy, Erick,Snell, Kristi D.,Strasburg, Gale M.,Frost
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p. 11587 - 11591
(2007/10/03)
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- Syntheses of Cyclic Triphenylantimony(V) Catecholates from Triphenylantimony, tert-Butyl Hydroperoxide, and Polyhydric Phenols
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Cyclic triphenylantimony(V) catecholates are prepared by reactions of triphenylantimony with polyhydric phenols (pyrogallol, hydroxyhydroquinone, and quercetin) in the presence of tert-butyl hydroperoxide. Triphenylantimony reacts with polyhydric phenols selectively at the o-hydroxy groups to give the corresponding Sb(V) derivatives.
- Dodonov,Fedorov,Zaburdyaeva
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p. 1460 - 1462
(2007/10/03)
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- Monooxovanadium(V) mixed ligand complexes of schiff bases and catecholates: Synthesis, spectral and electrochemical characterization
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Mixed ligand, monooxovanadium(V) complexes of Schiff bases with catechol, p-tertbutylcatechol or pyrogallol have been synthesized and characterized by various spectral techniques, such as FTIR, UV-vis, 51V NMR and electrochemistry. All of these complexes exhibited a six coordinated VO3+ center. The stability and the conversion of these complexes to pentacoordinated VO+2 species with the loss of a bidentate catecholate ligand in DMSO were demonstrated using absorption, 51V NMR and electrochemical studies. 51V NMR studies further suggested the formation of two possible isomers in the case of p-tertbutylcatechol and pyrogallol complexes of VO3+. Electrochemistry of these complexes showed one reversible V(V)/V(IV) couple and another irreversible V(IV)/V(III) response. The mixed ligand, VO3+ complexes are more resistant to reduction as compared to the corresponding tris catecholate complexes. Copyright
- Asgedom, Gebray,Sreedhara, Alavattam,Rao, Chebrolu P.,Kolehmainen, Erkki
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p. 3731 - 3739
(2008/10/09)
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- Benzopyranones, processes for their preparation and their use
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Described are 2H-1-benzopyran-2-ones (coumarin derivates) of general formula (I), STR1 wherein R1 is a hydroxyl group, a lower-alkoxy group, a cycloalkoxy group with 4 to 6 C-atoms or the alkyl- or arylsulphonyloxy group R6 --SO2 O--; R2 and R3, independently of each other, are hydrogen atoms, hydroxyl groups, lower-alkoxy groups or cycloalkoxy groups with 4 to 6 C-atoms; R4 is a hydrogen atom, a lower-alkyl group with 1 to 4 C-atoms or a phenyl group; Y is a nitrogen atom, a CH group or a COH group; R5 is a phenyl, naphtyl, pyridinyl or pyrimidinyl group which may optionally be substituted by one or two C1 -C5 alkyl groups, by one or two halogen atoms, by a halogen and C1 -C5 alkyl together, by perfluoroalkyl with 1 to 3 C-atoms, by C1 -C5 alkoxy, by hydroxy, by methylenedioxy or by nitro; R6 is a lower-alkyl group, a cycloalkyl group with 4 to 6 C-atoms or a phenyl group which may optionally be substituted by one or two C1 -C5 alkyl groups, by one or two halogen atoms, or by perfluoroalkyl with 1 to 3 C-atoms; and n=1 to 4; plus their addition compounds with physiologically tolerated acids. Also described are methods of preparing these compounds, novel intermediates in their preparation and methods of preparing such intermediates. The novel coumarin derivatives described possess a neuroprotective and psychopharmacological action. The invention also concerns pharmaceuticals containing these compounds.
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- Phototransformation of resorcinol induced by excitation of nitrite and nitrate ions. II: nitrate ions
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The excitation of nitrate ions in an aqueous solution of resorcinol (I) at pH = 5.5-6.5, leads to a mixture of 1,2,3-trihydroxybenzene (II), 1,2,4-trihydroxybenzene (III), 4-nitrosoresorcinol (V) and 4-nitroresorcinol (VII). A secondary formation of 2, 4-dinitrosoresorcinol (VI) was also detected.
- Machado,Boule
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p. 165 - 173
(2007/10/03)
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- Pyrolysis of some (13)C-labeled glucans: A mechanistic study
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An isotopic labeling study has been conducted to investigate the chemical mechanisms involved in the formation of certain pyrolysis products of glucans, specifically glycolaldehyde (GA), acetol (hydroxypropanone), acetic acid, and formic acid, which are the major non-aqueous components of the distillate fraction (-60 deg C condensate) of the pyrolyzate. (13)C labels at C-1, C-2, and C-6 of the glucose rings in synthetic glucans were used to reveal the origins of this compounds.In general, the results show that each compound is formed by several different mechanisms, but suggest that only a few mechanisms predominate in each case.Glycolaldehyde derives predominantly from the C-1-C-2 segment of the glucose monomers, with C-5-C-6 also contributing significantly.Evidence is presented supporting heterolytic mechanisms which require a reducing end-group and base catalysis.Acetol derives mostly from three contiguous carbons that include a terminal carbon (C-1 or C-6), most often C-6 and most often appearing as the methyl carbon in the acetol.Acetic acid also arises most often from terminal carbons, the C-5-C-6 segment being the major source, with the methyl carbon usually deriving from C-1 or C-6.About half of the formic acid produced arises from C-1.Mechanisms derived from the chemistry of alkaline degradation and involving acylformylcarbinol intermediates are proposed.
- Ponder, Glenn R.,Richards, Geoffrey N.
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- Formation of 1,2,4-benzenetriol by hydrothermal treatment of carbohydrates.
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Conversion of dilute aqueous solutions of 5-hydroxymethyl-2-furaldehyde and D-fructose under near-critical conditions led to the formation of 1,2,4-benzenetriol in relatively high yields.
- Luijkx, G. C. A.,Rantwijk, F. van,Bekkum, H. van
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p. 343 - 344
(2007/10/02)
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- Cycloheptaamylose as a model for starch in the pyrolysis of polysaccharides
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The pyrolysis of cycloheptaamylose has been studied as a model for starch. 1,6-Anhydro-β-D-glucopyranose (levoglucosan, LG, 7) and its furanose isomer are major products from vacuum pyrolysis at 280, 300, and 320°, with combined yields ranging from 38 to 50% of the substrate-dependent on temperature. Pyrolysis in methyl sulfoxide at 150° produced LG and glucose as well as gluco-oligosaccharides of d.p. up to 7, with both reducing and 1,6-anhydro end-groups. A mechanism is postulated in which the first step is the heterolytic scission of a glucosidic linkage to form a linear, seven-membered oligosaccharide having a glucosyl cation in place of the reducing end-group. The cation is stabilized either by intramolecular attack of O-6 on the C-1 cation or by intermolecular transglycosylation. The former product subsequently yields LG upon scission of a terminal glucosidic linkage. The pyrolysis of cycloheptaamylose has been studied as a model for starch. 1,6-Anhydro-β-D-glucopyranose (levoglucosan, LG, 7) and its furanose isomer are major products from vacuum pyrolysis at 280, 300, and 320°, with combined yields ranging from 38 to 50% of the substrate dependent on temperature. Pyrolysis in methyl sulfoxide at 150° produced LG and glucose as well as gluco-oligosaccharides of d.p. up to 7, with both reducing and 1,6-anhydro end-groups. A mechanism is postulated in which the first step is the heterolytic scission of a glucosidic linkage to form a linear, seven-membered oligosaccharide having a glucosyl cation in place of the reducing end-group. The cation is stabilized either by intramolecular attack of O-6 on the C-1 cation or by intermolecular transglycosylation. The former product subsequently yields LG upon scission of a terminal glucosidic linkage.
- Lowary,Richards
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p. 157 - 166
(2007/10/02)
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- Method for dealkylation of alkyl-aryl ethers
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A method is disclosed for the dealkylation of alkylaryl ethers by reaction with aluminum triodide under reflux. The reaction is carried out in the presence of a catalytic amount of a quaternary ammonium iodide in a substantially non-aqueous organic solvent. The reaction product is then hydrolyzed with water. The quaternary ammonium iodide can be of the formula R4 N+ I-, wherein R is alkyl, and the solvent is preferably benzene or cyclohexane.
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- Synthesis of Condensed Tannins. Part 17. Oligomeric (2R,3S)-3,3',4',7,8-Pentahydroxyflavans: Atropisomerism and Conformation of Biphenyl and m-Terphenyl Analogues from Prosopis glandulosa ('Mesquite')
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(2R,3S)-2,3-trans-3',4',7,8-Tetrahydroxyflavan-3-ol , the predominant metabolite in the heartwood of Prosopis glandulosa, represents a putative precursor of a variety of oligomers, including conventional - and -biflavan-3-ols, a -1,3-diarylpropylflavan-3-ol, - and atropisomeric -biphenyl-type biflavan-3-ols, and -m-terphenyl-type triflavan-3-ols.Other participants in these condensations are mainly (+)-catechin, and also the flavan-3,4-diol analogue of (+)-mesquitol.Oligomeric structures were confirmed by biomimetic oxidative and acid-induced couplings, and by nuclear Overhauser effect difference spectroscopy.These applications enabled correction of previous structural assignments for atropisomeric -(+)-mesquitol-(+)-catechins and -bis--(+)-catechins, and determination of their conformations.
- Young, Esme,Brandt, Edward V.,Young, Desmond A.,Ferreira, Daneel,Roux, David G.
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p. 1737 - 1750
(2007/10/02)
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- Microbial Production of Pyrogallol through Decarboxylation of Gallic Acid
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Cultural conditions for the microbial production from gallic acid of pyrogallol were investigated with Citrobacter sp.The maximal formation of pyrogallol was observed when the bacterium was cultured at 28 deg.C for 48 hr in a medium containing 2.0 percent gallic acid, 0.5 percent maltose, 0.2 percent (NH4)2HPO4, 0.1 percent KH2PO4, 0.05 percent KCl, 0.05 percent MgSO4.7H2O and 0.05 percent yeast extract (pH 6.0).Under these conditions, 7.2 g of pyrogallol was formed from 20 g of gallic acid added to one liter of the medium.Larger amounts of pyrogallol could be produced when gallic acidwas further added to the broth after 16-24 hr cultivation.The reaction was performed at pH 4.5 under anaerobic conditions using 1mM L-ascorbic acid and N2 gas.Seventy-five grams of gallic acid added to one liter of the broth was transformed to 54.1 g of pyrogallol under these conditions, with a yield of 97.4percent.
- Yoshida, Hajime,Yamada, Hideaki
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p. 659 - 664
(2007/10/02)
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- Heterogeneous Photocatalytic Decomposition of Phenol over TiO2 Powder
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The photocatalytic decomposition of phenol in oxygenated aqueous suspensions of lightly-reduced anatase TiO2, being the most satisfactory among the semiconductors in vestigated from the standpoint of the photocatalytic activity and stability, has been investigated at the optimum pH 3.5.The products at the initial stage of the reaction were hydroquinone, pyrocatechol. 1,2,4-benzenetriol, pyrrogallol, and 2-hydroxy-1,4-benzoquinone.These intermediates underwent further photocatalytic oxidation via acids and/or aldehydes finally into CO2 and H2O.A reaction scheme involving hydroxyl radicals as real reactive species has been proposed.Although H2O2 was formed via O2(-) produced by electron trapping of adsorbed oxygen, its concentration remained constant at a low value during the reaction.About 0.7 mole of O2 was consumed for the consumption of one mole of phenol at the initial stage of the reaction.These results indicated that hydroxyl radicals were formed not only via holes but also via H2O2 from O2(-).It was interesting from the viewpoint of wastewater treatment that phenol was completely mineralized to CO2 in the presence of TiO2 powder under solar irradiation without both aeration and mixing of the solution.
- Okamoto, Ken-ichi,Yamamoto, Yasunori,Tanaka, Hiroki,Tanaka, Masashi,Itaya, Akira
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p. 2015 - 2022
(2007/10/02)
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- THE FLUORIDE ION EFFECT IN THE REACTIONS OF SINGLET OXYGEN WITH ENOLS
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The fluoride ion effect in the reaction of enolic systems with singlet oxygen has been investigated. β-Dicarbonyl compounds yielded 1,2,3-tricarbonyl derivatives, some of which underwent further hydration, whereas α-diketones suffered oxidative decarboxylation to give open-chain aldehydo-acids or keto-acids.
- Wasserman, Harry H.,Pickett, James E.
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p. 2155 - 2162
(2007/10/02)
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- Isolation and Identification of a Pyrogallol Producing Bacterium from Soil
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A bacterial strain, which was isolated from soil, and identified as Citrobacter sp., showed an inducible gallic acid decarboxylase activity producing pyrogallol from gallic acid.The strain also decarboxylated protocatechuic acid, pyrocatechuic acid, 3,5-dihydroxybenzoic acid and m-hydroxybenzoic acid as well.The pyrogallol and pyrocatechol produced were isolated from the cultured broths to which gallic acid and protocatechuic acid were added, respectively.
- Yoshida, Hajime,Tani, Yoshiki,Yamada, Hideaki
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p. 2539 - 2546
(2007/10/02)
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- Process for preparing pyrogallol
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A pyrogallol compound of formula STR1 wherein R1, R2 and R3 each represent hydrogen or alkyl of 1-6 carbon atoms, or a salt thereof, is prepared by hydrolyzing the corresponding 2,2,6,6-tetrachlorocyclohexanone or 2,2,6,6-tetrabromocyclohexanone.
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- Process for preparing an organic compound
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Pyrogallol or a salt thereof is prepared by a process comprising deoximating cyclohexane-1,2,3-trione oxime or an oxime derivative thereof or a salt of either. Preferably the oxime itself is exployed, especially the 1,3-dioxime. The deoximation is preferably effected by hydrolysis.
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- Process for preparing tetrahalocyclohexanone
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2,2,6,6-Tetrachloro(or tetrabromo)cyclohexanone is prepared by reacting in the liquid phase chlorine or bromine with a cyclohexanone compound of formula STR1 where Y is hydrogen or chlorine (to produce the tetrachloro compound) or hydrogen or bromine (to produce the tetrabromo compound) in the presence as catalyst of an organophosphorus compound of formula STR2 where Z is chlorine or bromine; n is 0 or 1; and when n is 0, m is 0 or 2, R1 is alkyl or phenyl, and R2 and R3 are hydrogen, alkyl or phenyl; and when n is 1, m is 0, and R1, R2 and R3 are the same and each is STR3 alkyl or phenyl, or R1 is hydrogen and R2 and R3 are alkyl or phenyl; or a salt thereof. Each alkyl is of 1-10 carbon atoms.
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