cas 700-13-0, Trimethylhydroquinone | Articles data

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Kinetics of highly selective catalytic hydrogenation of 2,3,5-trimethylbenzoquinone on Raney nickel catalyst
This work focuses on the catalytic hydrogenation of 2,3,5-trimethylbenzoquinone (TMBQ) to 2,3,5-trimethylhydroquinone (TMHQ). Kinetic interpretation has been made by studying the important process parameters using Raney nickel as the catalyst. Thus, at 100% TMBQ conversion level, as high as 100% selectivity to TMHQ was accomplished. Experimentation was performed to acquire the most suitable process conditions from the viewpoint of process research and development.
Mukhopadhyay, Sudip,Chandnani, Kavita H.,Chandalia, Sampatraj B.
p. 254 - 258
(2000)
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Pd/UiO-66(Hf): A highly efficient heterogeneous catalyst for the hydrogenation of 2,3,5-trimethylbenzoquinone
The conversion of 2,3,5-trimethylbenzoquinone (TMBQ) to 2,3,5-trimethylhydroquinone is regarded as one of the most important reactions for the production of vitamin E. Here, we report on a Hf-based metal–organic framework (MOF), UiO-66(Hf), with supported palladium nanoparticles as a highly active, selective, and recyclable catalyst for the direct hydrogenation of TMBQ with H2 under mild reaction conditions. The developed Pd/UiO-66(Hf) catalyst exhibited a marked increase in activity compared with its Pd/UiO-66(Zr) counterpart and conventional Pd/C catalysts. Its excellent catalytic performance is ascribed to the large number of acid sites in the UiO-66(Hf) framework, which promote hydrogenation.
Cai, Xiaoxiong,Pan, Jianping,Tu, Gaomei,Fu, Yanghe,Zhang, Fumin,Zhu, Weidong
p. 23 - 26
(2018)
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Metal–organic framework derived Pd/ZrO2@CN as a stable catalyst for the catalytic hydrogenation of 2,3,5-trimethylbenzoquinone
Metal–organic frameworks (MOFs) have recently been identified as versatile sacrificing templates to construct functional nanomaterials for heterogeneous catalysis. Herein, we report a thermal transformation strategy to directly fabricate metal Pd nanoclusters inlaid within a ZrO2@nitrogen-doped porous carbon (Pd/ZrO2@CN) composite using Pd@NH2-UiO-66(Zr) as a precursor that was pre-synthesized by a one-pot hydrothermal method. The developed Pd/ZrO2@CN as a robust catalyst delivered remarkable stability and activity to the catalytic hydrogenation of 2,3,5-trimethylbenzoquinone (TMBQ) to 2,3,5-trimethylhydroquinone (TMHQ), a key reaction involved in vitamin E production. The hydrogenation was carried out at 110?°C with 1.0?MPa H2, and it resulted in 98% TMHQ yield as the sole product over five consecutive cycles, outperforming the analogue Pd/ZrO2@C without nitrogen doping templated from Pd@UiO-66(Zr). The excellent catalytic properties of Pd/ZrO2@CN likely originated from the highly stable ultrafine Pd nanoclusters inlaid within ZrO2@CN matrix on account of the strong interaction between N and Pd, as well as on the Lewis acidity of ZrO2, which was beneficial to the hydrogenation.
Li, Shasha,Pan, Jianping,Wu, Xiaoxue,Fu, Yanghe,Xiao, Qiang,Zhang, Fumin,Zhu, Weidong
(2019)
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PROCESS FOR THE PREPARATON OF HYDROQUINONES
The present invention relates to a process for the manufacturing the hydroquinones from the respective quinones in a cyclic alkyl carbonate using a reducing agent.
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Page/Page column 10

(2021/06/26)

FORMATION OF ALPHA TOCOPHEROL FROM 2,3,6-TRIMETHYLPHENOL
The present invention relates to the formation of α-tocopherol from 2,3,6- tri?methyl?phenol comprising the steps a) the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethylquinone. b) the reduction of 2,3,5-trimethylquinone to 2,3,5-trimethylhydroquinone c) the condensation of 2,3,5-trimethylhydroquinone and isophytol or a phytol derivative in such a manner that all reaction steps a), b) and c) are performed in cyclic alkylene carbonate solvent.
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Page/Page column 8; 15-16

(2021/06/26)

FORMATION OF 2,3,5-TRIMETHYLHYDROQUINONE FROM 2,3,6-TRIMETHYLPHENOL
The present invention relates to the formation of 2,3,5-trimethylhydro- quinone from 2,3,6-tri?methyl?phenol comprising the steps a) the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethylquinone. b) the reduction of 2,3,5-trimethylquinone to 2,3,5-trimethylhydroquinone in such a manner that both steps a) and b) are performed in cyclic alkylene carbonate solvent.
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Page/Page column 12; 13

(2021/06/26)

SYNTHESIS OF CHROMANOL AND 2-METHYL-1,4-NAPHTHOQUINONE DERIVATIVES
The present invention relates to a process for the production of chromanol and 2-methyl-1,4-naphthoquinone derivatives, more specifically to a process for preparing a compound of the general formula (I) or (II) wherein the variables are as defined in the claims and the description.
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Page/Page column 49-51; 61

(2020/03/05)

SYNTHESIS OF CHROMANOL DERIVATIVES
The present invention relates to a process for the production of chromanol derivatives, more specifically to a process for preparing a compound of the general formula I wherein R1, R2 and R3 independently of each other are selected from hydrogen and methyl, R4 is selected from C-1-C6-alkyl, and X is selected from C1-C20-alkyl and C2-C20-alkenyl.
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Page/Page column 40

(2020/03/05)

SYNTHESIS OF CHROMANOL DERIVATIVES
The present invention relates to a process for the production of chromanol derivatives, more specifically to a process for preparing a compound of the general formula (I) wherein R1, R2 and R3 independently of each other are selected from hydrogen and methyl, R4 is selected from hydrogen and C1-C6-alkanoyl, and X is selected from C1-C20-alkyl and C2-C20-alkenyl.
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Page/Page column 41

(2020/03/05)

Selective synthesis of benzoquinones over Cu(ii)-containing propylsalicylaldimine functionalized mesoporous solid catalysts
The major product, 2,3,5-trimethyl-1,4-benzophenone (TMBO), was synthesised by an eco-friendly liquid-phase oxidation of 2,3,6-trimethylphenol (TMP-OH) over Cu(ii)-containing propylsalicylaldimine (CSA) functionalized mesoporous solid catalysts, namely, CSASBA-15(0.2), CSASBA-15(0.1) and CSAMCM-41(0.2), synthesized using various amounts of copper in a simple post-grafting method using different mesoporous silica materials, e.g., thick-silica walled SBA-15 and thin-silica walled MCM-41. The benzoquinones, i.e., 2,6-disubstituted p-benzoquinones (DSBQs), were also synthesised by the slurry-phase oxidation of di/tri-substituted phenols using the prepared catalysts. A promising chemical treatment was used for the removal of extra-framework copper species from the active surface of CSASBA-15(0.2), and the catalytic activity of the recovered catalyst, i.e. green mesoporous CSASBA-15(0.2) or W-CSASBA-15(0.2), was evaluated. Various reaction parameters, oxidants and solvents were used in this catalytic oxidation. To confirm the catalytic stability, recyclability and hot-catalytic filtration experiments were performed. On the basis of all catalytic results, it is worth noting that the mesoporous CSASBA-15(0.2) is an outstanding and a promising heterogeneous catalyst for the selective synthesis of TMBO and DSBQs, and produces 98% TMBO selectivity with 100% TMP-OH conversion at 353 K for 40 min and 97-99% DSBQ selectivity with 98-100% di/tri-substituted phenols conversion at 330 K for 1-3 h. The green mesoporous catalyst has unprecedented catalytic activity compared with that of other CSA functionalized mesoporous solid catalysts.
Selvaraj, Manickam,Assiri, Mohammed A.
p. 3291 - 3299
(2019/03/13)

Preparation method of trimethylhydroquinone
The invention discloses a preparation method of trimethylhydroquinone. The preparation method is characterized in that isophorone is used as an initial raw material and oxidized into oxoisophorone, then an acylation reaction occurs in the oxoisophorone and an acylating agent to produce trimethyl hydroquinone diester, and the trimethyl hydroquinone diester is hydrolyzed to produce 2,3,5-trimethylhydroquinone. The method disclosed by the invention has cheap and easily-available raw materials and simple syntheses steps, a used solvent is easy to recover and reuse, and the method needs not use ofa big amount of acid and alkali, thereby reducing pollution of the environment, being convenient for large-scale industrial production and having good application prospects.
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Paragraph 0041; 0042; 0049; 0050; 0057; 0058; 0065; 0066

(2019/01/07)

Method for synthesizing trimethylhydroquinone through pseudocumene
The invention relates to a method for synthesizing trimethylhydroquinone through pseudocumene. The method for synthesizing the trimethylhydroquinone through the pseudocumene comprises the following steps that the pseudocumene is used as the raw material, a brominating reaction, an oxidizing reaction and a reduction reaction are conducted, and finally the trimethylhydroquinone is prepared. Please see the reaction formula in the specifications. According to the method for synthesizing the trimethylhydroquinone through the pseudocumene, the low-cost pseudocumene is used as the starting raw material, the process route is short, the yield is high, complete cyclic utilization of the bromine element can be achieved through recycling, the method for synthesizing the trimethylhydroquinone through the pseudocumene is a clean synthesizing technology, and the problems that in the prior art, m-cresol is in short supply, and serious pollution is caused in the p-xylene technology are solved.
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(2017/08/28)

An Enzymatic Route to α-Tocopherol Synthons: Aromatic Hydroxylation of Pseudocumene and Mesitylene with P450 BM3
Aromatic hydroxylation of pseudocumene (1 a) and mesitylene (1 b) with P450 BM3 yields key phenolic building blocks for α-tocopherol synthesis. The P450 BM3 wild-type (WT) catalyzed selective aromatic hydroxylation of 1 b (94 %), whereas 1 a was hydroxylated to a large extent on benzylic positions (46–64 %). Site-saturation mutagenesis generated a new P450 BM3 mutant, herein named “variant M3” (R47S, Y51W, A330F, I401M), with significantly increased coupling efficiency (3- to 8-fold) and activity (75- to 230-fold) for the conversion of 1 a and 1 b. Additional π–π interactions introduced by mutation A330F improved not only productivity and coupling efficiency, but also selectivity toward aromatic hydroxylation of 1 a (61 to 75 %). Under continuous nicotinamide adenine dinucleotide phosphate recycling, the novel P450 BM3 variant M3 was able to produce the key tocopherol precursor trimethylhydroquinone (3 a; 35 % selectivity; 0.18 mg mL?1) directly from 1 a. In the case of 1 b, overoxidation leads to dearomatization and the formation of a valuable p-quinol synthon that can directly serve as an educt for the synthesis of 3 a. Detailed product pattern analysis, substrate docking, and mechanistic considerations support the hypothesis that 1 a binds in an inverted orientation in the active site of P450 BM3 WT, relative to P450 BM3 variant M3, to allow this change in chemoselectivity. This study provides an enzymatic route to key phenolic synthons for α-tocopherols and the first catalytic and mechanistic insights into direct aromatic hydroxylation and dearomatization of trimethylbenzenes with O2.
Dennig, Alexander,Weingartner, Alexandra Maria,Kardashliev, Tsvetan,Müller, Christina Andrea,Tassano, Erika,Schürmann, Martin,Ruff, Anna Jo?lle,Schwaneberg, Ulrich
p. 17981 - 17991
(2017/11/29)

Method for preparing 2,3,5-trimethyl hydroquinone through biomimetic catalytic reduction
The invention discloses a method for preparing 2,3,5-trimethyl hydroquinone through biomimetic catalytic reduction. The method comprises: dissolving 2,3,5-trimethyl hydroquinone in a solvent, adding a biomimetic catalyst, leading hydrogen in, performing a catalytic hydrogenation reduction reaction at the room temperature under the normal pressure, performing reduced pressure distillation to remove the solvent from the obtained filtrate after the reaction is over, and performing extraction to take the catalyst out and to obtain 2,3,5-trimethyl hydroquinone. The catalytic hydrogenation reduction is mild in technical condition, simple to operate, and high in yield. The yield is no less than 95%. The prepared 2,3,5-trimethyl hydroquinone can be used for synthesizing vitamin E.
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Paragraph 0050-0056

(2017/05/27)

Reactivity and mechanism investigation of selective hydrogenation of 2,3,5-trimethylbenzoquinone on: In situ generated metallic cobalt
Efficient and inexpensive catalysts are urgently desired for the hydrogenation of 2,3,5-trimethylbenzoquinone (TMBQ) to 2,3,5-trimethylhydroquinone (TMHQ), a key vitamin-E intermediate. In this study, a one-step method was developed to synthesize uniform cobalt-based NPs supported on porous nitrogen-doped carbon for the hydrogenation of TMBQ to TMHQ. The as-prepared catalyst shows a high yield (>90%) and selectivity (>99%) for TMBQ hydrogenation as well as α,β-unsaturated carbonyls. The satisfactory performance is attributed to the small particle size and homogeneous distribution. Meanwhile, metallic Co is proved to be responsible for the catalytic activity. Furthermore, density functional theory calculation discloses that the excellent chemoselectivity towards TMBQ is due to the preference for a desorption process over sequential hydrogenation of TMHQ. This novel material has great potential as a non-precious-metal catalyst for heterogeneous hydrogenation processes, due to its outstanding catalytic performance, simple preparation method and low production cost.
Su, Diefeng,Wei, Zhongzhe,Mao, Shanjun,Wang, Jing,Li, Yi,Li, Haoran,Chen, Zhirong,Wang, Yong
p. 4503 - 4510
(2016/07/06)

Synthetic method for 2,3,5-trimethyl hydroquinone
The invention discloses a synthetic method for 2,3,5-trimethyl hydroquinone. In an existing synthetic method, two main side reactions are similar to the structure of a product, and consequently separation is very difficult. The synthetic method comprises the steps that a 2,3,5-trimethyl p-phenyl diquinone and alcohol solvent and a catalyst are mixed and then subjected to a hydrogenation reaction by introducing hydrogen into a high-pressure hydrogenation reaction kettle, and 2,3,5-trimethyl hydroquinone is obtained. The catalyst is a passivated raney nickel catalyst, in other words, a sulfurated compound is added in a raney nickel catalyst so as to reduce the activity of the raney nickel catalyst and improve reaction selectivity, wherein the sulfurated compound is any one or a mixture of two or more of sulfur dioxide, dimethyl sulfoxide, methyl mercaptan, hydrogen sulfide, ammonium sulfite, dimethyl sulfone and dimethyl sulfide. By means of the synthetic method, the cost of the catalyst for the hydrogenation reaction is reduced, the reaction selectivity is improved, and the quality of 2,3,5-trimethyl hydroquinone is improved.
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Paragraph 0029-0037; 0049

(2017/03/14)

A kind of environmental protection of the method for the synthesis of 2, 3, 5 - trimethyl hydroquinone
The invention relates to the field of chemical pharmacy, and in particular relates to an environment-friendly synthesis method for 2,3,5-trimethyl hydroquinone. The environment-friendly synthesis method for 2,3,5-trimethyl hydroquinone comprises the following steps: dissolving 1,2,4-trimethylbenzene serving as a raw material by using an organic solvent; adding hydrogen peroxide oxidant to oxidize 1,2,4-trimethylbenzene into 2,3,5-trimethyl p-benzoquinone to obtain a synthetic product; extracting the synthetic product to obtain an extract liquid; adding a reducing agent into the extract liquid; heating to perform a reduction reaction to synthesize 2,3,5-trimethyl hydroquinone. 1,2,4-trimethylbenzene serving as the raw material used in the synthesis method is inexpensive and easy to get; the used reaction reagents, for example, hydrogen peroxide, the organic solvent, the extraction agent and the reducing agent, are all commonly used reagents; moreover, the raw materials are low in cost; the used reagents can be recycled; the synthesis method has the advantages of mild reaction conditions, easiness in operation, a short process flow, low causticity on reaction equipment and low pollution to the environment, and is a green and environment-friendly industrial production line.
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Paragraph 0041; 0042; 0043-0046; 0049-0052; 0054-0061

(2019/02/02)

PROCESS FOR THE MANUFACTURE OF TMHQ
The present invention is directed to a process for the manufacture of 2,3,5-trimethyl-hydro-p-benzoquinone comprising the following steps: a) hydrogenating 2,6-dimethyl-p-benzoquinone with hydrogen in the presence of a hydrogenation catalyst in an organic solvent to obtain 2,6-dimethyl-hydro-p-benzoquinone; b) reacting 2,6-dimethyl-hydro-p-benzoquinone with a secondary amine and formal-dehyde in an organic solvent to obtain 2,6-dimethyl-3-(N,N-disubstituted aminomethyl)-hydro-p-benzoquinone; c) reacting 2,6-dimethyl-3-(N,N-disubstituted aminomethyl)-hydro-p-benzoquinone with hydrogen in the presence of a hydrogenolysis catalyst in an organic solvent to obtain 2,3,5-trimethylhydro-p-benzoquinone; wherein the organic solvent in all steps a), b) and c) is independently selected from the group consisting of methyl tert. -butyl ether, ethyl tert. -butyl ether, methyl tert. -amyl ether, methoxycyclopentane and any mixtures thereof. Preferably the organic solvent used in all steps a), b) and c) is the same.
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Page/Page column 34-35

(2012/03/26)

PROCESS FOR THE PREPARATION OF HYDROQUINONES
The invention relates to a process for the preparation of a hydroquinone compound of formula (I) wherein R2, R3, R5 and R6 have the meaning according to claim 1, with the steps of formylating a substituted phenol and oxidising the resulting substituted 4-hydroxy- benzaldehyde under acidic conditions to the corresponding hydroquinone of formula (I). Another object of the invention concerns the intermediate 2,3,5-trimethyl-4-hydroxy- benzaldehyde for synthesis of 2,3,5-trimethyl-hydroquinone (TMHQ) and (dl)cc-tocopherol.
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(2011/11/01)

An efficient reduction of quinones by formate-palladium/carbon system
Ammonium formate in presence of palladium-carbon is an efficient system for catalytic transfer hydrogenation of several functional groups under mild conditions. However, this system was not found effective for reduction of quinones to hydroquinones, although reduction could be effected with phosphinic acid, phosphinates or cyclohexene as donors. A reexamination of this reaction suggested that formates were good hydrogen donors in this reduction but the reaction was inhibited due to quinhydrone formation. A simple expedient of maintaining low concentration of quinone during catalytic transfer hydrogenation reduction gave excellent yields of the hydroquinone. Compared to formates, formic acid was found to be a poor hydrogen donor.
Pande, Poorn Prakash
experimental part
p. 2549 - 2553
(2010/11/05)

Involvement of semiquinone radicals in the in vitro cytotoxicity of cigarette mainstream smoke
Free radicals in cigarette smoke have attracted a great deal of attention because they are hypothesized to be responsible in part for several of the pathologies related to smoking. Hydroquinone, catechol, and their methyl-substituted derivatives are abundant in the particulate phase of cigarette smoke, and they are known precursors of semiquinone radicals. In this study, the in vitro cytotoxicity of these dihydroxybenzenes was determined using the neutral red uptake (NRU) assay, and their radical-forming capacity was determined by electron paramagnetic resonance (EPR). All of the dihydroxybenzenes studied were found to generate appreciable amounts of semiquinone radicals when dissolved in the cell culture medium employed in the NRU assay. Hydroquinone exhibited by far the highest capacity to form semiquinone radicals at physiological pH, even though it is not the most cytotoxic dihydroxybenzene. Methyl-substituted dihydroxybenzenes were found to be more cytotoxic than either hydroquinone or catechol. The formation of semiquinone radicals via auto-oxidation of the dihydroxybenzenes was found to be dependent on the reduction potential of the corresponding quinone/semiquinone radical redox couple. The capacity to generate semiquinone radicals was found to be insufficient to explain the variance in the cytotoxicity among the dihydroxybenzenes in our study; consequently, other mechanisms of toxicity must also be involved. The observed interactions between 2,6-dimethylhydroquinone and hydroquinone in the cytotoxicity assay and EPR analysis suggest that care needs to be taken when the bioactivity of cigarette smoke constituents is evaluated, i.e., the effect of the cigarette smoke complex matrix on the activity of the single constituent studied must be taken into consideration.
Chouchane, Salem,Wooten, Jan B.,Tewes, Franz J.,Wittig, Arno,Mueller, Boris P.,Veltel, Detlef,Diekmann, Joerg
p. 1602 - 1610
(2008/12/22)

In situ synthesis, characterization of SiPMo-X, and different catalytic properties of SiPMo-X and SiPW-X
SBA-15 frameworks with encapsulated Keggin type heteropolyacids (HPAs) were synthesized in situ under strongly acidic conditions (pH 2 adsorption-desorption isotherms and transmission electron microscopy (TEM), and their structure was systematically characterized by X-ray diffraction (XRD), UV/Vis diffuse reflectance-(DRS), infrared- (IR), and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Characterization results suggest that the samples show very ordered hexagonal mesostructure, and the HPAs that are incorporated into the framework of meso-silica are insoluble during catalysis. Results of catalytic tests indicate that the materials demonstrated catalytic activity comparable with or even surpassing those of the bulk HPAs in catalytic tests implementing chemical reactions of bulky molecules (1,3,5-tri-isopropylbenzene cracking, esterification of benzoic acid with tert-butyl alcohol, and 2,3,6-trimethylphenol hydroxylation with H 2O2). Additionally, some other properties, such as easy separation and stability when recycled, ensure their potential applications in the chemical industries. Here, we report not only the in situ synthesis and characterization of SiPMo-X, but also the difference in the catalytic properties of SiPMo-X and SiPW-X. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
Shi, Chunfeng,Wang, Runwei,Zhu, Guangshan,Qiu, Shilun,Long, Jun
p. 3054 - 3060
(2007/10/03)

Preparation of 1,4-hydrobenzoquinones by the PCC/SiO2-promoted double oxidation of 3-cyclohexene-1,2-diols
The PCC/SiO2-promoted double oxidation of 3-cyclohexene-1,2- diols, which were easily prepared by the two-step sequence of α-hydroxylation of various conjugated cyclohexenones and the subsequent nucleophilic carbonyl addition of alkyl anions, produced diversely substituted 1,4-hydrobenzoquinones. The Royal Society of Chemistry 2005.
Kim, Hee Jin,Koo, Sangho
p. 3479 - 3481
(2007/10/03)

Novel proton type beta zeolite, preparation method thereof and process for preparing phenol compound using the same
Disclosed are a proton type β zeolite in which an acid site showing a desorption peak with a range of ±100° C. with a center of 330° C. exists in a spectrum measured by the ammonia temperature programmed desorption method (NH3-TPD), and an amount of a strong acid site showing a desorption peak of 500° C. or higher is controlled to 2.5 μmol/g or less, a method for preparing the same, and a process for preparing a phenol compound by oxidizing a benzene compound with a peroxide in the presence of the proton type β zeolite.
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(2008/06/13)

First synthesis of rac-(5-2H3)-α-CEHC, a labeled analogue of a major vitamin E metabolite
Over the past few years, quantitative determination of α- and γ-CEHC, main urinary metabolites of vitamin E, has been becoming more and more important as a key parameter in assessing oxidative stress and supplementation of tocopherols. The use of deuterated analogues of these metabolites allows their accurate determination even in complex matrixes. While preparation of γ-CEHC-d2 has already been described, here we report the first synthesis of α-CEHC-d3 together with α-tocopheronolactone-d3, its oxidation product.
Mazzini, Francesco,Netscher, Thomas,Salvadori, Piero
p. 9303 - 9306
(2007/10/03)

A new process for the production of trimethylhydroquinone
A new synthetic method for trimethylhydroquinone(TMHQ), one of main feedstock for synthesis of vitamin E(VE), is reported. All commercial processes for TMHQ is via 2, 3, 6-trimethyl-benzoquinone and has disadvantages in their multi-steps and production of pollutants. To reduce the pollution and to decrease synthesis steps, an attempt has been made to develop a single-step process for TMHQ, i.e. direct hydroxylation of 2, 3, 6-trimethyl-phenol (TMP) with H2O2 over copper hydroxyphosphate (Cu 2(OH)PO4) catalyst. The results show that the catalyst is of high activity for hydroxylation of TMP and high selectivity for TMHQ. Some important factors affecting the catalytic activity and selectivity have been studied. A green process for the production of TMHQ could be developed with deep study.
Zhu,Chen
p. 1349 - 1354
(2007/10/03)

Photoreduction of p-Benzoquinones: Effects of Alcohols and Amines on the Intermediates and Reactivities in Solution
The photochemistry of 1,4-benzoquinone (BQ) and alkyl-, Cl- and related derivatives, e.g. methyl-, 2,6-dimethyl-, chloro-, 2,5-dichloro-1,4-benzoquinone, duroquinone and chloranil, was studied in nonaqueous solvents by UV-vis spectroscopy using nanosecond laser pulses at 308 nm. The reactivity of the triplet state (3Q*) of the quinones with 2-propanol in the absence of water is largest for BQ and depends mainly on the quinone structure, whereas the rate constant of electron transfer from amines, such as triethylamine (TEA) or 1,4-diazabicyclo[2.2.2]octane, is close to the diffusion-controlled limit for BQ and most derivatives. Photoinduced charge separation after electron transfer from amines to 3Q* and the subsequent charge recombination or neutralization are supported by time-resolved conductivity measurements. The half-life of the decay kinetics of the semiquinone radical (.QH/Q.-) depends significantly on the donor and the medium. The photoconversion into the hydroquinones was measured under various conditions, the quantum yield, λirr = 254 nm, increases with increasing 2-propanol and TEA concentrations. The effects of quenching of 3Q*, the .QH/Q.- radicals and the photoconversion are outlined. The mechanisms of photoreduction of quinones in acetonitrile by 2-propanol are compared with those by TEA in benzene and acetonitrile, and the specific properties of substitution are discussed.
Goerner, Helmut
p. 440 - 448
(2007/10/03)

Photoprocesses of p-Benzoquinones in Aqueous Solution
The photochemistry of 1,4-benzoquinone (BQ) and several derivatives, for example, duroquinone, trimethyl-2,5- or 2,6-dimethyl-, and methyl-BQ in aqueous solution or mixtures with polar media, for example, acetonitrile or 2,2,2-trifluoroethanol, was studied by time-resolved UV-vis spectroscopy after pulses at 248 and 308 nm. The triplet state and the semiquinone radical (?QH/Q?-) of BQs are spectroscopically and kinetically separated intermediates. The radical yield in the absence of H-atom donors is low and significantly increased in the presence of alcohols. Efficient photoinduced charge formation, because of Q?- and H+ after H-atom transfer from 2-propanol to the triplet state, and small effects in the absence of a donor were observed by transient conductivity. The quantum yield of photodecomposition, λirr = 254 nm, is substantial for BQ, MeBQ, and Me2BQs in aqueous solution, but small for Me 4BQ. To account for the efficient photoconversion of BQs into hydrobenzoquinones and 2-hydroxy-1,4-benzoquinones, a novel water-mediated reaction not involving free radicals is proposed as major step. This mechanism is consistent with the prediction that the observed triplet state is monomeric and the yield of Q?-, detected by both transient absorption and conductivity, is low for sub-millimolar BQ, MeBQ, and Me2BQs at pH 5-6. In addition, H-atom abstraction from a polar organic solvent or by self-quenching plays a role in mixtures with water or at enhanced quinone concentration, respectively.
Goerner, Helmut
p. 11587 - 11595
(2007/10/03)

Process for preparing trimethylhydroquinone diacetate and trimethylhydroquinone
A process for preparing trimethylhydroquinone diacetate, with subsequent hydrolysis to give trimethylhydroquinone, the process including reacting 2,2,6-trimethylcyclohexane-1,4-dione under oxidative conditions, in the presence of a sulfonating agent and a strong acid, and in the presence of an acylating agent.
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(2008/06/13)

Process for preparing trimethylhydroquinone diacetate and trimethylhydroquinone
A process for preparing trimethylhydroquinone diacetate, with subsequent hydrolysis to give trimethylhydroquinone, the process including reacting 2,2,6-trimethylcyclohexane-1,4-dione under oxidative conditions, in the presence of a sulfonating agent and a strong acid, and in the presence of an acylating agent.
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Example 4

(2008/06/13)

Reductive and Bioreductive Activation is Controlled by Electronic Properties of Substituents in Conformationally-Constrained Anticancer Drug Delivery Systems
Conformationally-constrained, anticancer drug delivery systems (TDDS) containing the methyl ester of melphalan (as a model drug) were synthesized using electron-withdrawing or electron-donating functional groups to modulate reductive and bioreductive activation. The electronic nature of substituents in TDDS was found to control reductive and bioreductive activation of TDDS, thus influencing drug delivery from TDDS.
Weerapreeyakul, Natthida,Visser, Petra,Brummelhuis, Mathijn,Gharat, Laxmikant,Chikhale, Prashant J.
p. 148 - 163
(2007/10/03)

Method for producing trimethylhydroquinone diester
This method provides trimethylhydroquinone diester by using a recyclable catalyst which shows high activity and operability in the reaction, while reducing the risk of corrosion of the reactor. The method for the production of 2,5,6-trimethylhydroquinone diester comprises reacting 2,6,6-trimethylcyclohexe-2-en-1,4-dione with an acylating agent in the presence of a solid catalyst. The acylating agent includes a C2-4 carboxylic acid anhydride (e.g. acetic anhydride) and a C2-4 carboxylic acid halide (e.g. acetyl chloride). The solid catalyst includes a solid acid catalyst (e.g. strongly or super-strongly acidic ion exchange resin, compound oxide, zeolite, heteropoly acid).
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(2008/06/13)

Process for the production of trimethylhydroquinone diesters and of trimethylhydroquinone
An improved process for the production of 2,3,5-trimethylhydroquinone by rearrangement of 4-oxoisophorone (ketoisophorone, 3,5,5-trimethyl-2-cyclohexen-1,4-dione) to yield a trimethylhydroquinone diester and the subsequent saponification thereof. Trimethylhydroquinone is in turn an important starting material for the production of vitamin E.
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(2008/06/13)

Method of making d,l-α-tocopherol
A process for the manufacture of d,l-α-tocopherol by condensing trimethylhydroquinone with isophytol comprises carrying out the condensation in the presence of a polyperfluoroalkylenesulphonic acid as the catalyst and in a solvent, especially an aprotic solvent. The catalyst is preferably a polyperfluoroalkylenesulphonic acid from the Nafion series, e.g., Nafion NR 50 or Nafion 117.
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(2008/06/13)

Reductive activation of conformationally-constrained, anticancer drug delivery systems
Redox-active substituents were used to modulate reduction potentials in conformationally-constrained, drug delivery systems. The extent of drug delivery was proportional to the degree of reductive activation, which was influenced by the electronic properties of the substituents. Such reductively-activated carrier systems can be used to achieve controlled drug delivery to bioreductive regions in hypoxic solid tumors.
Gharat, Laxmikant,Visser, Petra,Brummelhuis, Mathijn,Guiles, Ronald,Chikhale, Prashant
p. 444 - 456
(2007/10/03)

Comparative pulse radiolysis studies of alkyl- and methoxy-substituted semiquinones formed from quinones and hydroquinones
Absorption spectra and rate constants for the disproportionate of 12 alkyl- and methoxy-substituted semiquinone anion free radicals (Q?-) produced by the one-electron reduction (using CO2?- as a reductant) of 1,4-benzoquinones and 1,4-naphthoquinone (Q) as well the oxidation (using N3? as an oxidant) of the corresponding hydroquinones (QH2) were determined by pulse radiolysis in 50 mM sodium phosphate buffer, pH 7.40 at room temperature. Both spectral and kinetic characteristics of Q?- only moderately depended on whether Q?- was produced from Q or QH2. Spectra of benzosemiquinones display two peaks with maximum at 310-320 nm and ca. 430 nm with the ratio of about 2-2.5. Molar absorption coefficients were determined. Rate constants for Q?- disproportionation (2k1) were correlated with the nature of substituents. While 2k1 was scarcely affected by methyl substitution, Q?- containing isopropyl, tert-butyl and methoxy substituents were visibly more stable than non-substituted and methyl-substituted Q?-.
Roginsky, Vitaly A.,Pisarenko, Leonid M.,Bors, Wolf,Michel, Christa,Saran, Manfred
p. 1835 - 1840
(2007/10/03)

New Route to Trimethylhydroquinone
A new route to trimethylhydroquinone has been proposed that involves cycloaromatization of isonitrosoacetylacetone with methyl ethyl ketone to form 2,3,5-trimethyl-4-nitrosophenol, which is subsequently deoximated into 2,3,5-trimethyl-1,4-benzoquinone and then reduced to trimethylhydroquinone.
Belyaev, E. Yu.,Tovbis, M. S.,Semichenko, E. S.,Orlovskaya, N. F.
p. 506 - 507
(2007/10/03)

Acylaminophenol compounds
The invention relates to the compounds of formula (I): STR1 in which R represents higher alkyl, 1-(higher alkyl)lower cycloalkyl-1-yl or higher alkenyl comprising one or more double bonds, and either R3 represents hydroxyl, R1 and R2, which are different, represent hydrogen or lower alkyl, R4 and R5, which are identical or different, represent lower alkyl or alkoxy, or R1 and R4 represent hydroxyl and R2, R3 and R5, which are identical or different, represent lower alkyl or alkoxy, their isomers as well as their salts, and a method for treating an animal or human living body afflicted with dylipidemias or atherosclerosis.
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(2008/06/13)

Synthesis of plastoquinone derivatives with different structures of the side chain
Two schemes for the synthesis of plastoquinone derivatives with ω-substituted alkyl side chains have been developed, based on radical alkylation of 2,3-dimethyl-1,4-benzoquinone with ω-substituted carboxylic and/or dicarboxylic acids in the presence of S2O82- and Ag+.In Scheme 1, radical alkylation of 2,3-dimethyl-1,4-benzoquinone with 11-bromoundecanoic acid, in the presence of (NH4)2S2O8 and AgNO3, gave 2,3-dimethyl-5-(10-bromodecyl)-1,4-benzoquinone, which, after hydration, gave 2,3-dimethyl-5-(10-hydroxydecyl)-1,4-benzoquinone.Esterification of 2,3-dimethyl-5-(10-hydroxydecyl)-1,4-benzoquinone with different acyl chlorides gave 2,3-dimethyl-5-(10-acyloxydecyl)-1,4-benzoquinone.In Scheme 2, radical alkylation of 2,3-dimethyl-1,4-benzoquinone with adipic acid, in the presence of K2S2O8 and AgNO3, gave 2,3-dimethyl-5-(4-carboxybutyl)-1,4-benzoquinone, which was converted to 2,3-dimethyl-5--1,4-benzoquinone by esterification with different alcohols in the presence of dicyclohexylcarbodiimide. 2,3-Dimethyl-5-(8-carboxyoctyl)-1,4-benzoquinone and 2,3-dimethyl-5--1,4-benzoquinone were similarly synthesized from 2,3-dimethyl-1,4-benzoquinone and sebacic acid.Plastoquinone derivatives having different kinds of double bonds in the side chain with and without a 6-methyl group were synthesized from 2,3,5-trimethyl-1,4-benzoquinone and 2,3-dimethyl-1,4-benzoquinone by successive reactions with (1) NaBH4; (2) KHSO4, different kinds of allylic alcohols; (3) Ag2O.The allylic alcohols were prepared from their corresponding aldehydes by reduction with NaBH4. 2,3,6-Trimethyl-1,4-benzoquinone by radical methylation with acetic acids in the presence of K2S2O8 + AgNO3.
Liu, Benli,Gu, Lianquan,Zhang, Jingling
p. 104 - 110
(2007/10/02)

THE GENERATION OF C,O,O-TRILITHIATED DERIVATIVES OF DIHYDRIC PHENOLS
Halogenated dihydric phenols (hydroquinones and resorcinols) undergo halogen metal exchange with nBuLi/TMEDA/THF or ether (inverse addition) under sonication, thereby generating a C,O,O-trilithiated species which can be trapped with electrophiles.
Saa, Jose M.,Morey, Jeroni,Suner, Guillem,Frontera, Antoni,Costa, Antoni
p. 7313 - 7316
(2007/10/02)

RELATIONS HOLDING IN THE REACTIONS OF TRIMETHYLPHENOLS WITH PEROXYACETIC ACID
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Kharchuk, V. G.,Kolenko, I. P.
p. 819 - 826
(2007/10/02)

Reduction of carbonyl compounds promoted by silicon hydrides under the influence of trimethylsilyl-based reagents
The synthetic utility of hydrosilanes under the influence of trimethylsilyl-based reagents as new reducing systems is described. 1,1,3,3-Tetramethyldisiloxane (TMDS) reagent in combination with iodotrimethylsilane or bromotrimethylsilane produces alkyl halides from aldehydes in good to excellent yields.Polymethylhydrosiloxane (PMS) in the presence of iodotrimethylsilane also produces benzyl iodides in excellent yields.On the contrary, PMS reagent was found unsuitable for the synthesis of benzyl bromides.Similary, TMDS reagent in combination with trimethylsilyl triflate produces symmetrical ethers from aldehydes without concomitant formation of competitive products.Under similar conditions, PMS reagent failed to provide the expected symmetrical ethers and Friedel-Crafts products were formed.Reduction of quinones to hydroquinones is also described.
Aizpurua, Jesus M.,Lecea, Begona,Palomo, Claudio
p. 2342 - 2347
(2007/10/02)

REACTION OF 1,2,4-TRIMETHYLBENZENE WITH PERACETIC ACID
The oxidation of 1,2,4-trimethylbenzene with peracetic acid leads to the formation of trimethylphenols and hydroquinones, which undergo transformations to the corresponding benzoquinones and products from oxidative cleavage of the ring.The controlling stage of the process is the electrophilic hydroxylation of 1,2,4-trimethylbenzene.
Kharchuk, V. G.,Kolenko, I. P.,Petrov, L. A.,Gus'kova, L. M.
p. 2071 - 2078
(2007/10/02)

REAGENTS AND SYNTHETIC METHODS 52. SILANE REDUCTION OF CARBONYL COMPOUNDS IN THE PRESENCE OF IODINE.
Synthetic utility of 1,1,3,3,-tetramethyldisiloxane (TMDS) reagent under the influence of iodine is described.TMDS reagent in combination with iodine produces alkyl iodides from carbonyl compounds and oxiranes in good to excellent yields.Reduction of quinones into hydroquinones is also described.The mentioned transformations are explained from mechanistic points of view.
Lecea, B.,Aizpurua, J. M.,Palomo, C.
p. 4657 - 4666
(2007/10/02)

Process for the preparation of 4-hydroxy-2,4,6-trimethyl-2,5-cyclohexadienone
4-Hydroxy-2,4,6-trimethyl-2,5-cyclohexadienone is prepared by treatment of 2,4,6-trimethylphenol with a halogenation agent and water in the presence of an organic solvent which is inert to the halogenation agent.
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(2008/06/13)

DISCRETE RADICAL SPECIES DEPENDENT UPON SOLVENT AS DETECTED BY CIDNP IN THE LIGHT-INDUCED ELECTRON TRANSFER FROM HYDROQUINONES TO PHEOPHYTIN α
Light-induced electron transfer from hydroquinones to Phe α was studied by means of CIDNP technique.Depending upon the solvent, electron transfer proceeds in different manners.In benzene, ion radical pair; hydroquinone cation radical and Phe α.-, of the triplet spin multiplicity was formed, whereas neutral radical pair; phenoxyl radical and Phe α-H., of the singlet spin multiplicity in methanol.
Maruyama, Kazuhiro,Furuta, Hiroyuki,Otsuki, Tetsuo
p. 1509 - 1510
(2007/10/02)

Preparation of chromane derivatives
Chromane derivatives (I) STR1 where R1, R2 and R3 are H or C1 -C8 -alkyl, R4 is H, C1 -C8 -alkyl or C1 -C8 -acyl and R5 is C1 -C8 -alkyl are prepared by reacting a hydroquinone (II) STR2 with a Lewis acid or a Lewis acid derivative having the same action, and with a nitrile CH2 =CH--C(R5)(OR6)CN (III), where R6 is H, C1 -C4 -acyl or C1 -C4 -alkyl, or with a compound from which III is formed in situ, in the presence of an inert solvent.
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(2008/06/13)

Allylation of Quinones with Allyltin Reagents
Lewis acid (BF3) catalyzed allylation of quinones with allyl- (2a), 2-methyl-2-propenyl- (2b), trans-2-butenyl- (2c,d), 3-methyl-2-butenyl- (2e,f), and trans-cinnamyltrialkyltin (2g) gives the corresponding allylhydroquinones with high regioselectivity.Vitamin K2(5) (7) and coenzyme Q1 (9) were prepared in yields of 78 and 75percent, respectively.These reactions appear to proceed through allylquinol intermediates which undergo rearrangement under the influence of BF3.The success of this synthesis of vitamin K2(5) and coenzyme Q1 depends on the fact that the reaction of 3-methyl-2-butenyltin with quinones occurs at the α carbon of the allylic system.
Naruta, Yoshinori
p. 3774 - 3783
(2007/10/02)

Process for preparing dihydric phenol derivatives
A process for preparing dihydric phenol derivatives by oxidizing monohydric phenol derivatives with hydrogen peroxide in the presence of a ketone. This reaction can be promoted in the presence of sulfuric acid or a salt thereof or a sulfonic acid or a salt thereof.
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(2008/06/13)

Process for preparing trimethylhydroquinone
This invention is directed to a process for preparing trimethylhydroquinone (TMHQ) by heating 4-hydroxy-2,4,6-trimethyl-2,5-cyclohexadiene-1-one (HTCD) in a nonacidic liquid medium consisting of either methanol or an aqueous medium, preferably in the presence of a basic substance, at a temperature of at least 100°C., and preferably 150°-300°C. Thus, according to this invention, TMHQ of high purity and small coloration can be prepared from HTCD in good yield, for example, as high as 85 - 98%.
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(2008/06/13)