- Helical-Shaped Bis-1,4-benzoxathiines through an Inverse-Electron-Demand Hetero-Diels–Alder Reaction of ortho-Thioquinones
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The reaction of transient ortho-thioquinones, which act as electron-poor dienes, with properly designed bis-dienophiles leads to the formation of helical-shaped bis-benzoxathiine cycloadducts with complete control of the regiochemistry and the relative stereochemistry. Bis-benzoxathiines were the result of two consecutive inverse-electron-demand cycloaddition processes with stereospecific approach of the diene anti to the bis-dienophile. The helical-shaped structure of the final products was demonstrated spectroscopically and confirmed by single-crystal X-ray analysis.
- Viglianisi, Caterina,Menichetti, Stefano,Piantini, Sara,Tofani, Lorenzo
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- Flavonoids in the poisonous plant oxytropis falcata
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Three new flavonoids, oxytropisoflavans A (1) and B (2) and (6aR,11aR)-3,8-dihydroxy-9,10-dimethoxypterocarpan (3), together with 30 known flavonoids (4-33), were isolated from the aerial parts and roots of Oxytropis falcata. The absolute configurations of 3 and C-3 in 1 and 2 were deduced by circular dichroism. The structure of flavonoid 2 was confirmed by single-crystal X-ray diffraction analysis and that of flavonoid 3 by total synthesis of its racemate. Oxytropisoflavan A (1) is an unprecedented chalcan-isoflavan biflavonoid, whereas oxytropisoflavan B (2) possesses a rare modified A-ring. Pterocarpan 3 has good radical-scavenging activity in the 1,1-diphenyl-2- picrylhydrazyl (DPPH) assay.
- Chen, Wen-Hao,Wang, Rui,Shi, Yan-Ping
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- Polyoxometalate-based supramolecular porous frameworks with dual-active centers towards highly efficient synthesis of functionalized: P -benzoquinones
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Selective oxidation of substituted phenols is an ideal method for preparing functionalized p-benzoquinones (p-BQs), which serve as versatile raw materials for the synthesis of a variety of biologically active compounds. Herein, two new polyoxometalate-based supramolecular porous frameworks, K3(H2O)4[Cu(tza)2(H2O)]2[Cu(Htza)2(H2O)2][BW12O40]·6H2O (1) and H3K3(H2O)3[Cu(Htza)2(H2O)]3[SiW12O44]·14H2O (2) (Htza = tetrazol-1-ylacetic acid), were synthesized and structurally characterized by elemental analysis, infrared spectroscopy, thermal analysis, UV-vis diffuse reflectance spectroscopy, and single-crystal X-ray and powder diffraction. The single-crystal X-ray diffraction analysis indicates that both compounds possess unique petal-like twelve-nucleated Cu-organic units composed of triangular and hexagonal metal-organic loops. In 1, the Cu-organic units are isolated and [BW12O40]5- polyoxoanions are sandwiched between staggered adjacent triangular channels in the structure. However in 2, the Cu-organic units extend into a two-dimensional layered structure, and the [SiW12O44]12- polyoxoanions occupy the larger hexagonal channels in the stacked structure. Both compounds as heterogeneous catalysts can catalyze the selective oxidation of substituted phenols to high value-added p-BQs under mild conditions (60 °C) with TBHP as the oxidant, particularly in the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-p-benzoquinone (TMBQ, key intermediate in vitamin E production). Within 8-10 min, the yield of TMBQ is close to 100%, and oxidant utilization efficiency is up to 94.2% for 1 and 90.9% for 2. The turnover frequencies of 1 and 2 are as high as 5000 and 4000 h-1, respectively. No obvious decrease in the yield of TMBQ was observed after five cycles, which indicates the excellent sustainability of both compounds. Our study of the catalytic mechanism suggests that there is a two-site synergetic effect: (i) the copper ion acts as the catalytic site of the homolytic radical pathway; and (ii) the polyoxoanion acts as the active center of the heterolytic oxygen atom transfer pathway. This journal is
- An, Haiyan,Chang, Shenzhen,Chen, Yanhong,Huang, Yaohui,Luo, Huiyun,Zhu, Qingshan
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p. 8591 - 8603
(2021/11/17)
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- Rational design, synthesis and biological evaluation of ubiquinone derivatives as IDO1 inhibitors
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Indoleamine 2,3-dioxygenase 1 (IDO1) is an attractive therapeutic target for the treatment of cancer, chronic viral infections and neurological disorders characterized by pathological immune stimulation. Herein, a series of known metal-chelating ubiquinone derivatives were designed, synthesized and evaluated for the IDO1 inhibiting activities. The docking studies showed that the compounds 11, 16, 18 and coenzyme-Q1 exhibited different binding modes to IDO1 protein. Among these compounds, the most active compound is 16d with an IC50 of 0.13 μM in enzymatic assay. The results reveal that a possible halogen bonding interaction between the bromine atom (3-Br) and Cys129 significantly enhances the inhibition activity against IDO1. This study provides structural insights of the interactions between ubiquinone analogues and IDO1 protein for the further modification and optimization.
- Ding, Yuyang,Tang, Fei,Xue, Xiaoqian,Luo, Jinfeng,Hussain, Muzammal,Huang, Yanhui,Wang, Zhen,Jiang, Hao,Tu, Zhengchao,Zhang, Jiancun
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- Bioinspired Total Synthesis of Bussealin e
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The first total synthesis of bussealin E, a natural product with a unique cycloheptadibenzofuran scaffold, is reported. A strategy inspired by a proposed biosynthesis was employed whereby a diphenylpropane derivative underwent an oxidative phenolic coupling to forge the tetracyclic ring system. The synthesis of the diphenylpropane featured a key sp2-sp3 Hiyama coupling between a vinyldisiloxane and a benzylic bromide.
- Twigg, David G.,Baldassarre, Leonardo,Frye, Elizabeth C.,Galloway, Warren R. J. D.,Spring, David R.
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p. 1597 - 1599
(2018/03/23)
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- Photochromic coenzyme Q derivatives: Switching redox potentials with light
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Coenzyme Q is an important redox cofactor involved in a variety of cellular processes, and is thus found in several cell compartments. We report a photochromic derivative of coenzyme Q that combines the molecular structures of the redox active cofactor and a photochromic dye. Light irradiation triggers an electronic rearrangement reversibly changing the redox potential. We used this effect to control the intermolecular redox reaction of the photochromic coenzyme Q derivative with dihydropyridine in solution by light irradiation. On mitochondria, the altered redox properties showed an effect on the respiratory chain. The experiments demonstrate that the redox reactions can be initiated inside the system of interest through irradiation with light and the accompanied photoisomerization.
- Simeth, Nadja A.,Kneuttinger, Andrea C.,Sterner, Reinhard,K?nig, Burkhard
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p. 6474 - 6483
(2017/08/29)
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- Synthesis of coenzyme Q0 through divanadium-catalyzed oxidation of 3,4,5-trimethoxytoluene with hydrogen peroxide
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The selective oxidation of methoxy/methyl-substituted arenes to the corresponding benzoquinones has been first realized using aqueous hydrogen peroxide as a green oxidant, acid tetrabutylammonium salts of the γ-Keggin divanadium-substituted phosphotungstate [γ-PW10O38V2(μ-O)2]5- (I) as a catalyst, and MeCN as a solvent. The presence of the dioxovanadium core in the catalyst is crucial for the catalytic performance. The reaction requires an acid co-catalyst or, alternatively, a highly protonated form of I can be prepared and employed. The industrially relevant oxidation of 3,4,5-trimethoxytoluene gives 2,3-dimethoxy-5-methyl-1,4-benzoquinone (ubiquinone 0 or coenzyme Q0, the key intermediate for coenzyme Q10 and other essential biologically active compounds) with 73% selectivity at 76% arene conversion. The catalyst retains its structure under turnover conditions and can be easily recycled and reused without significant loss of activity and selectivity.
- Zalomaeva, Olga V.,Evtushok, Vasilii Yu.,Maksimov, Gennadii M.,Maksimovskaya, Raisa I.,Kholdeeva, Oxana A.
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p. 5202 - 5209
(2017/04/27)
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- Efficient cross-coupling of aryl/alkenyl triflates with acyclic secondary alkylboronic acids
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Aryl-secondary alkyl cross-coupling with aryl sulfonate esters as coupling partners remains a significant challenge. Efficient cross-coupling between aryl/alkenyl triflates and acyclic secondary alkylboronic acids is realized for the first time to provide a series of sterically congested acyclic secondary alkyl arenes/olefins in good to excellent yields. The employment of sterically bulky P,PO ligand L1/L2 is crucial for the high yields and selectivities. The method has enabled a concise and 4-step synthesis of a key intermediate of male contraceptive agent and PAF antagonist gossypol.
- Si, Tengda,Li, Bowen,Xiong, Wenrui,Xu, Bin,Tang, Wenjun
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p. 9903 - 9909
(2017/12/12)
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- ONO-pincer ruthenium complex-bound norvaline for efficient catalytic oxidation of methoxybenzenes with hydrogen peroxide
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The enhanced catalytic activity of ruthenium complex-bound norvaline Boc-l-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.
- Yoshida, Ryota,Isozaki, Katsuhiro,Yokoi, Tomoya,Yasuda, Nobuhiro,Sadakane, Koichiro,Iwamoto, Takahiro,Takaya, Hikaru,Nakamura, Masaharu
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supporting information
p. 7468 - 7479
(2016/08/16)
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- Efficient synthesis of sterically hindered arenes bearing acyclic secondary alkyl groups by suzuki-miyaura cross-couplings
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Bulky P,P-O ligands were designed to inhibit isomerization and reduction side reactions during the cross coupling between sterically hindered aryl halides and alkylboronic acids. Suzuki-Miyaura cross-couplings between di-ortho-substituted aryl bromides and acyclic secondary alkylboronic acids have been achieved with high yields. The method has also enabled the preparation of ortho-alkoxy di-ortho-substituted arenes bearing isopropyl groups in excellent yields. The utility of the synthetic method has been demonstrated in a late-stage modification of estrone and in the application to a new synthetic route toward gossypol. No side reaction: The shown bulky P,P-O ligands (right) successfully inhibit isomerization and reduction side reactions of the cross-coupling of sterically hindered substrates such as di-ortho-substituted aryl bromides with acyclic secondary alkylboronic acids. The method also allows the preparation of ortho-alkoxy di-ortho-substituted isopropyl arenes in excellent yields.
- Li, Chengxi,Chen, Tianyu,Li, Bowen,Xiao, Guolan,Tang, Wenjun
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p. 3792 - 3796
(2015/03/18)
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- Synthesis of an Isotopically Labeled Naphthalene Derivative That Supports a Long-Lived Nuclear Singlet State
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The synthesis of an octa-alkoxy substituted isotopically labeled naphthalene derivative, shown to have excellent properties in singlet NMR experiments, is described. This highly substituted naphthalene system, which incorporates an adjacent 13C spin pair, is readily accessed from a commercially available 13C2-labeled building block via sequential thermal alkynyl- and arylcyclobutenone rearrangements. The synthetic route incorporates a simple desymmetrization approach leading to a small difference in the chemical shifts of the 13C spin pair, a design constraint crucial for accessing nuclear singlet order. (Chemical Equation Presented).
- Hill-Cousins, Joseph T.,Pop, Ionut-Alexandru,Pileio, Giuseppe,Stevanato, Gabriele,H?kansson, P?r,Roy, Soumya S.,Levitt, Malcolm H.,Brown, Lynda J.,Brown, Richard C. D.
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supporting information
p. 2150 - 2153
(2015/05/13)
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- Differing selectivities in mechanochemical versus conventional solution oxidation using Oxone
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A mechanochemical oxidation of methoxylated aromatic chemicals is described, providing an example of a very different selectivity as compared to solution-based chemistry. Oxone was shown to react with 1,2,3-trimethoxybenzene to yield predominantly 2,6-dimethoxybenzoquinone in the solid state or 2,3,4-trimethoxyphenol in solution. The difference in effective acidity of the reaction conditions was not apparently responsible for the observed selectivity. The mechanochemical method described is simple, reproducible, and gave higher yield at higher conversion of substrate compared to solution conditions.
- Collom,Anastas,Beach,Crabtree,Hazari,Sommer
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p. 2344 - 2347
(2013/06/27)
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- Method for dyeing keratinous fibres using an aminoindole in combination with a quinone derivative
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Method for dyeing keratinous fibres, characterized in that at least one composition (A) containing at least one aminoindole in a medium appropriate for dyeing is applied to these fibres, the application of the composition (A) being preceded or followed by the application of a composition (B) containing, in a medium appropriate for dyeing, at least one quinone derivative chosen from ortho- or para-benzoquinones, ortho- or para-benzoquinone monoimines or diimines, 1,2- or 1,4-naphthoquinones, ortho- or para-benzoquinone sulphonimides, α,ω-alkylene-bis-1,4-benzoquinones, or 1,2- or 1,4-naphthoquinone monoimines or diimines, the aminoindoles and the quinone derivatives being chosen such that the difference in redox potential ΔE between the redox potential Ei of the aminoindoles, determined at pH 7 in a phosphate medium on a vitreous carbon electrode by voltametry, and the redox potential Eq of the quinone derivative, determined at pH 7 in a phosphate medium by polarography on a mercury electrode relative to the saturated calomel electrode, in such that
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- Process for dyeing keratinous fibres with a hydroxyindole in combination with a quinone derivative; and novel 1,4-benzoquinones
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Process for dyeing keratinous fibres, comprising the step of applying to these fibres at least one composition A containing, in a medium appropriate for dyeing, at least one mono- or di-hydroxyindole the application of the composition A being preceded or followed by the application of a composition B containing, in a medium appropriate for dyeing, at least one quinone derivative chosen from ortho- or para-benzoquinones, monoimines or diimines of ortho- or para-benzoquinones, 1,2- or 1,4-naphthoquinones, sulphonimides of ortho- or para-benzoquinones, α, ω-alkylene-bis-1,4-benzoquinones, or 1,2- or 1,4-naphthoquinone-monoimines or -diimines; the mono- or di-hydroxyindoles and the quinone derivatives being chosen such that the oxidation-reduction potential difference ΔE between the oxidation-reduction potential Ei of the mono- or di-hydroxyindoles, determined at pH 7 in a phosphate medium on a vitreous carbon electrode by voltametry, and the oxidation-reduction potential Eq of the quinone derivative determined at pH 7 in a phosphate medium by polarography on a mercury electrode and relative to a saturated calomel electrode is such that
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- Oxidation of Methoxy- and/or Methyl-Substituted Benzenes and Naphthalenes to Quinones and Phenols by H2O2 in HCOOH
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The oxidation of a number of arenes (methoxybenzenes, methylbenzenes, and naphthalenes) to quinones and phenols by H2O2 in HCOOH has been examined.Methoxybenzenes were much more easily oxidized to p-benzoquinones than methylbenzenes (e.g., 1,3,5-trimethoxybenzene was oxidized to 2,6-dimethoxy-p-benzoquinone in a 75percent yield and 1,2,4-trimethylbenzene to 2,3,5-trimethyl-p-benzoquinone in a 16percent yield).Electron-withdrawing substituents, such as nitro, cyano, and chloro groups, lowered the conversion of reactants and changed the product selectivity from quinones to phenols.Methoxybenzonitriles were oxidized to corresponding phenols in a moder ate yield (e.g., 2,6-dimethoxybenzonitrile to 3-hydroxy-2,6-dimethoxybenzonitrile in a 39percent yield and a 64percent selectivity).
- Orita, Hideo,Shimizu, Masao,Hayakawa, Takashi,Takehira, Katsuomi
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p. 1652 - 1657
(2007/10/02)
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- Rearrangement of 4-Alkynylcyclobutenones. A New Synthesis of 1,4-Benzoquinones
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A new convergent synthesis of 1,4-benzoquinones from 4-alkynyl-4-alkoxy(or hydroxy or trimethylsilyloxy)cyclobutenones is described.The required cyclobutenones are prepared from squaric acid and converted to the quinones upon mild thermolysis.The reaction proceeds via electrocyclic ring opening of the required cyclobutenones to (2-alkynylethenyl)ketenes, which then ring close to unique diradical intermediates.These then give the quinone products.The scope and mechanism of this unusual rearrangement are discussed.
- Foland, Lafayette D.,Karlsson, J. Olle,Perri, Steven T.,Schwabe, Rudolf,Xu, Simon L.,et al.
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p. 975 - 989
(2007/10/02)
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- Chinone von Benzo- und Dibenzokronenethern
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The preparation of the 1,4-quinones of benzocrown-5 (1), benzocrown-6 (2), and dibenzocrown-6 (3) and their quinols is described.The quinones are obtained by Fremy salt oxidation of the corresponding 3-hydroxybenzo-crown ethers which are readily accessible by a double protective group synthesis from 1,2,3-trihydroxybenzene.The synthetic pathway also provides a general high yield preparation of 2,3-dialkoxy-1,4-benzoquinones.The new crown ethers are characterised by 1H- and 13C-N.M.R. as well as U.V. spectroscopy.Non-aqueous redox potentials aredetermined by cyclic voltammetry.Crystalline complexes of 1 and 2 with various ammonium, alkali, and alkaline earth cations are also described.
- Dietl, F.,Gierer, G.,Merz, A.
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p. 626 - 631
(2007/10/02)
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- An Improved Synthesis of 1,4-Benzo- and 1,4-Naphthoquinones Bearing Active Substituents
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The synthesis of 1,4-benzoquinones and 1,4-naphthoquinones 3a-j carrying substituents such as methoxyl, allyl or oxiranyl was substantially improved.The 1-methoxy-4-methoxymethyloxy 2a-d, g-k or 1,4-bis(methoxymethyloxy) derivatives 2e-f were used, as a substrates instead of 1,4-dimethoxy derivatives 1a-j hitherto used and they were oxidized with silver(II) dipicolinate.Among numerous examples, the synthesis of a new analog of ubiquinone 3d with the oxiranyl substituent, being a new bioactivated alkylating agent, is reported.
- Syper, Ludwik,Kloc, Krystian,Mlochowski, Jacek
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p. 808 - 822
(2007/10/02)
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- COPPER-CATALYZED AEROBIC OXIDATION OF METHOXYPHENOLS
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A variety of methoxyphenols were selectively converted methoxy-p-benzoquinones by the use of copper-catalyzed aerobic oxidation.
- Matsumoto, Masakatsu,Kobayashi, Hisako,Hotta, Yasushi
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p. 515 - 520
(2007/10/02)
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- Electronic Control of Stereoselectivity. 9. The Stereochemical Course of Electrophilic Additions to Aryl-Substituted Benzobicyclooctadienes
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Product and relative reactivity data have been obtained for the photooxygenation, epoxidation, cyclopropanation, oxymercuration, and hydroboration of three differently substituted (aryl) 2-methylbenzobicyclooctadienes.Syn stereoselectivity was observed in every case, with the level of syn attack being highest with the tetrafluoro derivative 2c (except in the Simmons-Smith reaction where a single isomer was produced in every case).Only small differences in rate were seen with a given reagent.Electronic interactions in these molecules were explored by photoelectron spectroscopy and MINDO/3 calculations.These combined tools served to show that through-space interaction is absent in these molecules.However, through-bond coupling in 2a and 2b leads to olefinic ?-bond disrotation.The relative importance of this effect as well as long-range Coulomb and charge-transfer interactions is discussed.A connection between such subtle electronic influences and stereoselectivity is established, although prevailing steric effects do serve to compress somewhat the syn/anti range available to these systems.
- Paquette, Leo A.,Bellamy, Francois,Wells, Gregory J.,Boehm, Michael C.,Gleiter, Rolf
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p. 7122 - 7133
(2007/10/02)
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