108-46-3Relevant articles and documents
Deoxygenation of polyhydroxybenzenes: An alternative strategy for the benzene-free synthesis of aromatic chemicals
Hansen, Chad A.,Frost
, p. 5926 - 5927 (2002)
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
Mechanism and Structure of γ-Resorcylate Decarboxylase
Sheng, Xiang,Patskovsky, Yury,Vladimirova, Anna,Bonanno, Jeffrey B.,Almo, Steven C.,Himo, Fahmi,Raushel, Frank M.
, p. 3167 - 3175 (2018)
γ-Resorcylate decarboxylase (γ-RSD) has evolved to catalyze the reversible decarboxylation of 2,6-dihydroxybenzoate to resorcinol in a nonoxidative fashion. This enzyme is of significant interest because of its potential for the production of γ-resorcylate and other benzoic acid derivatives under environmentally sustainable conditions. Kinetic constants for the decarboxylation of 2,6-dihydroxybenzoate catalyzed by γ-RSD from Polaromonas sp. JS666 are reported, and the enzyme is shown to be active with 2,3-dihydroxybenzoate, 2,4,6-trihydroxybenzoate, and 2,6-dihydroxy-4-methylbenzoate. The three-dimensional structure of γ-RSD with the inhibitor 2-nitroresorcinol (2-NR) bound in the active site is reported. 2-NR is directly ligated to a Mn2+ bound in the active site, and the nitro substituent of the inhibitor is tilted significantly from the plane of the phenyl ring. The inhibitor exhibits a binding mode different from that of the substrate bound in the previously determined structure of γ-RSD from Rhizobium sp. MTP-10005. On the basis of the crystal structure of the enzyme from Polaromonas sp. JS666, complementary density functional calculations were performed to investigate the reaction mechanism. In the proposed reaction mechanism, γ-RSD binds 2,6-dihydroxybenzoate by direct coordination of the active site manganese ion to the carboxylate anion of the substrate and one of the adjacent phenolic oxygens. The enzyme subsequently catalyzes the transfer of a proton to C1 of γ-resorcylate prior to the actual decarboxylation step. The reaction mechanism proposed previously, based on the structure of γ-RSD from Rhizobium sp. MTP-10005, is shown to be associated with high energies and thus less likely to be correct.
Synthetic Study on Acremoxanthone A: Construction of Bicyclo [32.2]nonane CD Skeleton and Fusion of AB Rings
Hirano, Yoichi,Tokudome, Kensei,Takikawa, Hiroshi,Suzuki, Keisuke
, p. 214 - 220 (2017)
Toward the total synthesis of acremoxanthone A, a model study has revealed a convergent approach to construct the ABCDE ring system. The key steps include: (1) an effective construction of the bicyclo[3.2.2]nonane skeleton, (2) protocol for generating the bridgehead anion and trapping, and (3) 1,3-dipolar cycloaddition of a nitrile oxide to the internal alkene.
Spectroscopy of hydrothermal reactions 23: The effect of OH substitution on the rates and mechanisms of decarboxylation of benzoic acid
Li, Jun,Brill, Thomas B.
, p. 2667 - 2673 (2003)
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.
Carbodiimides as Acid Scavengers in Aluminum Triiodide Induced Cleavage of Alkyl Aryl Ethers
Sang, Dayong,Wang, Jiahui,Zheng, Yun,He, Jianyuan,Yuan, Caili,An, Qing,Tian, Juan
, p. 2721 - 2726 (2017)
A practical procedure for the cleavage of alkyl aryl ethers containing labile functional groups has been developed using aluminum triiodide as the ether cleaving reagent. Carbodiimides, typically used as dehydration reagents for the coupling of amines and carboxylic acids to yield amide bonds, are found to be effective hydrogen iodide scavengers that prevent acid-labile groups from deterioration. The method is applicable to variant alkyl aryl ethers such as eugenol, vanillin, ortho -vanillin and methyl eugenol. Suitable substrates are not limited to alkyl o -hydroxyphenyl ethers.
Polymorphism in isomeric dihydroxybenzoic acids
Sarma, Bipul,Sanphui, Palash,Nangia, Ashwini
, p. 2388 - 2399 (2010)
Multifunctional molecules are capable of assembling via different supramolecular synthons, or hydrogen bond motifs, between the same or different functional groups, leading to the possibility of polymorphism. We have employed sublimation and melt crystallization to generate two new crystalline polymorphs of 3,5-dihydroxybenzoic acid (DHBA), and a second form for 2,3-dihydroxybenzoic acid and 3,4-dihydroxybenzoic acid each. Since hydroxybenzoic acids tend to give solvate/hydrate crystal structures by solution crystallization, solvent-free methods are necessary to obtain single crystals of unsolvated forms. In addition to guest-free polymorphs, a new hydrate polymorph of 3,4-dihydroxybenzoic acid was crystallized from cold water. Polymorphs of dihydroxybenzoic acids differ in the number of symmetry-independent molecules (Z'), the nature of the hydrogen bond synthon, the molecular packing, and the unit cell parameters. Structural and thermal characterization of polymorphic phases shows that the commercial material matches with the high Z' phase for 2,3-DHBA, 3,5-DHBA, and 3,4-DHBA hydrate even though a low Z' crystal structure is known in each case. Solventless crystallization conditions at high temperature are a practical method to generate new guest-free polymorphs and high Z' crystal structures for high affinity functional group compounds.
A characterization of the two-step reaction mechanism of phenol decomposition by a Fenton reaction
Valdés, Cristian,Alzate-Morales, Jans,Osorio, Edison,Villase?or, Jorge,Navarro-Retamal, Carlos
, p. 16 - 22 (2015)
Phenol is one of the worst contaminants at date, and its degradation has been a crucial task over years. Here, the decomposition process of phenol, in a Fenton reaction, is described. Using scavengers, it was observed that decomposition of phenol was mainly influenced by production of hydroxyl radicals. Experimental and theoretical activation energies (Ea) for phenol oxidation intermediates were calculated. According to these Ea, phenol decomposition is a two-step reaction mechanism mediated predominantly by hydroxyl radicals, producing a decomposition yield order given as hydroquinone > catechol > resorcinol. Furthermore, traces of reaction derived acids were detected by HPLC and GS-MS.
A {110} facet predominated Bi6O6(OH)3(NO3)3·1.5H2O photocatalyst: Selective hydrothermal synthesis and its superior photocatalytic activity for degradation of phenol
Yang, Li-Min,Zhang, Guo-Ying,Liu, Yue,Xu, Yan-Yan,Liu, Chun-Mei,Liu, Jing-Wang
, p. 79715 - 79723 (2015)
A basic bismuth(iii) nitrate photocatalyst with the composition of Bi6O6(OH)3(NO3)3·1.5H2O (BBN) was facilely synthesized using a hydrothermal strategy via incomplete hydrolysis of bismuth nitrate. Characterization of the composition, morphology, microstructure, optical absorption, BET surface area, and photocatalytic behavior was systematically explored. The results indicated that BBN architectures built up of multilayered meshing-teeth structures with predominant {110} side facets can be selectively obtained by fine-tuning the reaction parameters. The sample exhibits an obviously superior photocatalytic activity for the degradation of phenol compared with BBN sheets with dominant top {001} planes and commercial P25, with the rate constant k improved by 3.6 and 2.8 fold, respectively. The excellent photocatalytic behavior combined with the rather low BET surface area of 0.0453 m2 g-1 indicate that the highly reactive {110} facets in BBN are responsible for the photocatalysis. The active oxidation species and main intermediates in the phenol/BBN system are ascertained using scavenger experiments and high performance liquid chromatography (HPLC) techniques. Combining the band edge of BBN and the redox potentials of the active species, a possible migration mechanism of photogenerated e-/h+ pairs on the surface of BBN is proposed. This work provides some new insights for the rational design and synthesis of active-facet exposed basic salt photocatalysts with excellent efficiency.
Radiation-induced Degradation of Nitrobenzene in Aqueous Solutions
Feng, Shao-Hong,Zhang, Shu-Juan,Yu, Han-Qing,Li, Qian-Rong
, p. 718 - 719 (2003)
Both the efficiency and pathways of nitrobenzene degradation induced by γ-ray irradiation were significantly influenced by the addition of reactive species scavengers. Experimental results showed that the degradation of nitrobenzene was more favorable und
Polyhedral Pt vs. spherical Pt nanoparticles on commercial titanias: Is shape tailoring a guarantee of achieving high activity?
Kovács,Fodor, Sz.,Vulpoi,Schrantz,Dombi,Hernádi,Danciu,Pap, Zs.,Baia
, p. 156 - 167 (2015)
As shape tailoring is gaining more attention in the field of photocatalysis, exploration of the impact of noble metal (Pt) nanoparticles' morphology on the activity of TiO2-Pt nanocomposites is inevitable. Spherical and polyhedral Pt nanoparticles have been synthesized by chemical reduction, while Aldrich anatase, Aldrich rutile, and Aeroxide P25 were used as base photocatalysts. The nanocomposites were analyzed using DRS, XRD, and HRTEM to uncover morphological, optical, and structural peculiarities of the composite photocatalysts. The importance of the Pt nanoparticles' geometry was proven at three levels: (i) UV light-driven photodegradation of three model pollutants: phenol, methyl orange, and oxalic acid; (ii) the primary degradation intermediates' evolution profile in the case of phenol degradation; and (iii) photocatalytic H2 production.
