- Methylation with Dimethyl Carbonate/Dimethyl Sulfide Mixtures: An Integrated Process without Addition of Acid/Base and Formation of Residual Salts
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Dimethyl sulfide, a major byproduct of the Kraft pulping process, was used as an inexpensive and sustainable catalyst/co-reagent (methyl donor) for various methylations with dimethyl carbonate (as both reagent and solvent), which afforded excellent yields of O-methylated phenols and benzoic acids, and mono-C-methylated arylacetonitriles. Furthermore, these products could be isolated using a remarkably straightforward workup and purification procedure, realized by dimethyl sulfide‘s neutral and distillable nature and the absence of residual salts. The likely mechanisms of these methylations were elucidated using experimental and theoretical methods, which revealed that the key step involves the generation of a highly reactive trimethylsulfonium methylcarbonate intermediate. The phenol methylation process represents a rare example of a Williamson-type reaction that occurs without the addition of a Br?nsted base.
- Chan, Bun,Lui, Matthew Y.,Lui, Yuen Wai
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- Facile Synthesis of Chiral Arylamines, Alkylamines and Amides by Enantioselective NiH-Catalyzed Hydroamination
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Regio- and enantioselective hydroarylamination, hydroalkylamination and hydroamidation of styrenes have been developed by NiH catalysis with a simple bioxazoline ligand under mild conditions. A wide range of enantioenriched benzylic arylamines, alkylamines and amides can be easily accessed by nitroarenes, hydroxylamines and dioxazolones, respectively as amination reagents. The chiral induction in these reactions is proposed to proceed through an enantiodifferentiating syn-hydronickellation step.
- Meng, Lingpu,Yang, Jingjie,Duan, Mei,Wang, You,Zhu, Shaolin
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supporting information
p. 23584 - 23589
(2021/09/28)
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- Specific Residues Expand the Substrate Scope and Enhance the Regioselectivity of a Plant O-Methyltransferase
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An isoeugenol 4-O-methyltransferase (IeOMT), isolated from the plant Clarkia breweri, can be engineered to a caffeic acid 3-O-methyltransferase (CaOMT) by replacing three consecutive residues. Here we further investigated functions of these residues by constructing the triple mutant T133M/A134N/T135Q as well as single mutants of each residue. Phenolics with different chain lengths and different functional groups were investigated. The variant T133M improves the enzymatic activities against all tested substrates by providing beneficial interactions to residues which directly interact with the substrate. Mutant A134N significantly enhanced the regioselectivity. It is meta-selective or even specific against most of the tested substrates but para-specific towards 3,4-dihydroxybenzoic acid. The triple mutant T133M/A134N/T135Q benefits from these two mutations, which not only expand the substrate scope but also enhance the regioselectivity of IeOMT. On the basis of our work, regiospecific methylated phenolics can be produced in high purity by different IeOMT variants.
- Tang, Qingyun,Bornscheuer, Uwe T.,Pavlidis, Ioannis V.
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p. 3227 - 3233
(2019/07/04)
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- Design, synthesis and pharmacological evaluation of novel antiinflammatory and analgesic O-benzyloxime compounds derived from natural eugenol
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Background: A new series of O-benzyloximes derived from eugenol was synthesized and was evaluated for its antinociceptive and anti-inflammatory properties. Methods: The target compounds were obtained in good global 25-28% yields over 6 steps, which led us to identify compounds (Z)-5,6-dimethoxy-2,2-dimethyl-2,3-dihydro-1H-inden-1-one-O-(4- (methylthio)benzyloxime (8b), (Z)-5,6-dimethoxy-2,2-dimethyl-2,3-dihydro-1H-inden-1-one-O-4- bromobenzyloxime (8d) and (Z)-5,6-dimethoxy-2,2-dimethyl-2,3-dihydro-1H-inden-1-one-O-4- (methylsulfonyl)benzyloxime (8f) as promising bioactive prototypes. Results: These compounds have significant analgesic and anti-inflammatory effects, as evidenced by formalin-induced mice paw edema and carrageenan-induced mice paw edema tests. In the formalin test, compounds 8b and 8f evidenced both anti-inflammatory and direct analgesic activities and in the carrageenan-induced paw edema, with compounds 8c, 8d, and 8f showing the best inhibitory effects, exceeding the standard drugs indomethacin and celecoxib. Conclusion: Molecular docking studies have provided additional evidence that the pharmacological profile of these compounds may be related to inhibition of COX enzymes, with slight preference for COX-1. These results led us to identify the new O-benzyloxime ethers 8b, 8d and 8f as orally bioactive prototypes, with a novel structural pattern capable of being explored in further studies aiming at their optimization and development as drug candidates.
- Da Silva, Rodrigo César,Veiga, Fabiano,Vilela, Fabiana Cardoso,Pereira, André Victor,Da Silva Cunha, Thayssa Tavares,Tesch, Roberta,Viegas, Claudio,Dias, Danielle Ferreira,Giusti-Paiva, Alexandre,Veloso, Marcia Paranho,Fraga, Carlos Alberto Manssour
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p. 1157 - 1166
(2019/10/28)
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- Cleavage of lignin C-O bonds over a heterogeneous rhenium catalyst through hydrogen transfer reactions
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Hydrogenolysis is one of the most popular strategies applied in the depolymerization of lignin for the production of aromatic chemicals. Currently, this strategy is mainly conducted under high hydrogen pressure, which can pose safety risks and is not sustainable and economical. Herein, we reported that heterogeneous rhenium oxide supported on active carbon (ReOx/AC) exhibited excellent activity in the selective cleavage of lignin C-O bonds in isopropanol. High yields of monophenols (up to 99.0%) from various lignin model compounds and aromatic liquid oils (>50%) from lignin feedstock were obtained under mild conditions in the absence of H2. The characterization of the catalyst by X-ray absorption fine structure, X-ray photoelectron spectroscopy and H2-temperature-programed reduction suggested that the activity of ReOx/AC could be attributed to the presence of ReIV-VI. The interaction between the surface oxygen groups of the active carbon and rhenium oxide could also play an important role in the cleavage of the C-O bonds. Notably, an ReOx/AC-catalyzed C-O bond cleavage pathway beyond a typical deoxydehydration mechanism was disclosed. More importantly, 2D-HSQC-NMR and GPC characterizations showed that ReOx/AC exhibited high activity not only in β-O-4 cleavage, but also in the deconstruction of more resistant β-5 and β-β linkages in lignin without destroying the aromatic ring. This study paves the way for the development of rhenium-based catalysts for the controlled reductive valorization of realistic lignin materials through a hydrogen transfer pathway.
- Zhang, Bo,Qi, Zaojuan,Li, Xinxin,Ji, Jianwei,Zhang, Leilei,Wang, Hua,Liu, Xiaoyan,Li, Changzhi
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supporting information
p. 5556 - 5564
(2019/10/28)
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- Lewis base-assisted Lewis acid-catalyzed selective alkene formation via alcohol dehydration and synthesis of 2-cinnamyl-1,3-dicarbonyl compounds from 2-aryl-3,4-dihydropyrans
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Acid-catalyzed dehydration of alcohols has been widely employed for the synthesis of alkenes. However, activated alcohols when employed as substrates in dehydration reactions are often plagued by the lack of alkene selectivity. In this work, the reaction system can be significantly improved through enhancing the performance of Lewis acid catalysts in the dehydration of activated alcohols by combining with a Lewis base. Observations of the reaction mechanism revealed that the Lewis base component might have changed the reaction rate order. Although both the principal and side reaction rates decreased, the effect was markedly more observed on the latter reaction. Therefore, the selectivity of the dehydration reaction was improved. On the basis of this observation, a new route to synthesize 2-cinnamyl-1,3-dicarbonyl compounds was developed by using 2-aryl-3,4-dihydropyran as a starting substrate in the presence of a Lewis acid/Lewis base combined catalyst system.
- Liu, Changhui,Pan, Bin,Gu, Yanlong
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p. 979 - 986
(2016/07/06)
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- Synthesis, characterization and in vitro biological evaluation of [Ru(η6-arene)(N,N)Cl]PF6 compounds using the natural products arenes methylisoeugenol and anethole
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Abstract Five new organometallic Ru(II) compounds (VI-X) with the general formula [Ru(η6-arene)(N,N)Cl]PF6, where arene-N,N correspond to methylisoeugenol-bipyridine (VI); anethole-bipyridine (VII); methylisoeugenol-ethylenediamine (VIII); anethole-ethylenediamine (IX) and methylisoeugenol-1,2-diaminobenzene (X), have been synthesized, fully characterized and biologically evaluated in vitro. The reaction conditions based on the reduction of [Ru(1,5-COD)Cl2]n in situ with methyleugenol and estragole, which are natural ligands, induced an alkene isomerization on the allylic substituent of coordinated arenes. The Ru(II)-arene bond formation and isomerization of the CC bond on the allyl substituent was confirmed using 1H NMR spectroscopy; this result was validated for compound VIII by X-ray diffraction. An XRD analysis revealed the presence of both enantiomers of the complex in the single-crystal. Compounds IX and X exhibited a better cytotoxic activity in vitro than carboplatin, which is a commercial drug, against three human tumor cell lines (MCF-7, PC-3 and HT-29).
- Delgado, Ricardo A.,Galdámez, Antonio,Villena, Joan,Reveco, Patricio G.,Thomet, Franz A.
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p. 131 - 137
(2015/04/14)
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- Catalytic cyclometallation of allylbenzenes by EtAlCl2 and Mg as new route to synthesis of dibenzyl butane lignans
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The cyclometallation of allylbenzenes (Ar = Ph, 4-MeO-Ph, 3,4-(MeO)2-Ph) with EtAlCl2 (Et2AlCl) and Mg in the presence of Zr and Ti catalysts (Dzhemilev reaction) has been studied. The reaction run with high diastereoselectivity and gives cyclic organoaluminum compounds, which deuterolysis or hydrolysis gave 2R(S), 3R(S)-dibenzyl butanes with yield of 48-69%. The study of catalyst structure effect on the substrate conversion, reaction chemo- and stereoselectivity showed that the best results were obtained in the case of Cp2ZrCl2 among the tested complexes. The enantioselectivity of neomenthylindenyl or neomenthyltetrahydroindenyl zirconium catalysts in the reaction did not exceed 20%ee. The trans-configuration of the substitutes in the metallacycles formed in the reaction has been proved by X-ray analysis of the hydrolysis product - 2R(S), 3R(S)-dimethyl-1,4-bis[(4′- methoxyphenyl)methyl]-butane. The proposed method could be used for the one-pot diastereoselective synthesis of dibenzyl butane lignans from readily available allylbenzenes.
- Parfenova, Lyudmila V.,Berestova, Tatyana V.,Kovyazin, Pavel V.,Yakupov, Aydar R.,Mesheryakova, Ekaterina S.,Khalilov, Leonard M.,Dzhemilev, Usein M.
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p. 292 - 298
(2015/02/19)
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- Selective route to 2-propenyl aryls directly from wood by a tandem organosolv and palladium-catalysed transfer hydrogenolysis
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A tandem organosolv pulping and Pd-catalysed transfer hydrogenolysis depolymerisation and deoxygenation has been developed. The tandem process generated 2-methoxy-4-(prop-1-enyl)phenol in 23 % yield (92 % theoretical monomer yield) starting from pine wood and 2,6-dimethoxy-4-(prop-1-enyl)phenol in 49 % yield (92 % theoretical monomer yield) starting from birch wood. Only endogenous hydrogen from wood was consumed, and the reaction was performed using green solvents.
- Galkin, Maxim V.,Samec, Joseph S.M.
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p. 2154 - 2158
(2014/11/08)
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- Total synthesis of cyclogalgravin and its dicarboxyl analog using sc(otf)3-mediated highly diastereoselective ring expansion of 1-(arylhydroxymethyl)cyclopropanecarboxylates
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The total synthesis of cyclogalgravin and its dicarboxyl analog was achieved by using the SmI2-promoted Reformatsky type reaction and Sc(OTf)3-mediated diastereoselective ring expansion as key steps.
- Sakuma, Daichi,Ito, Junki,Sakai, Ryo,Taguchi, Ryota,Nishii, Yoshinori
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supporting information
p. 610 - 611
(2014/05/20)
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- Ruthenium-catalyzed one-pot synthesis of (E)-(2-arylvinyl)boronates through an isomerization/cross-metathesis sequence from allyl-substituted aromatics
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We described the efficient preparation of (E)-(2-arylvinyl)boronates from allylbenzene derivatives on the basis of an isomerization/cross-metathesis sequence catalyzed by a modified Hoveyda-Grubbs catalyst. The implementation of the experimental procedure was simple and compatible with a large variety of substrates. This methodology provides a new chemical transformation not described to date. Allyl-substituted aromatics can thus be converted into diversely functionalized compounds, such as (E)-stilbene derivatives or (E)-vinyl azides, in only two steps. Copyright
- Hemelaere, Remy,Caijo, Frederic,Mauduit, Marc,Carreaux, Francois,Carboni, Bertrand
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supporting information
p. 3328 - 3333
(2014/06/09)
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- Synthesis and SAR comparative studies of 2-allyl-4-methoxy-1-alkoxybenzenes as 15-lipoxygenase inhibitors
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A group of 2-alkoxy-5-methoxyallylbenzene were designed, synthesised and evaluated as potential inhibitors of the soybean 15-lipoxygenase (SLO) on the basis of the eugenol and esteragol structures. Compound 4d showed the best half maximal inhibitory concentration (IC50) for SLO inhibition (IC 50=5.9±0.6 μM). All the compounds were docked in the SLO active site retrieved from the Research Collaboratory for Structural Bioinformatics (RCSB) Protein Data Bank (PDB entry: 1IK3) and showed that the allyl group of the synthetic compounds similar to the linoleic acid double bond, were oriented toward the Fe3+-OH moiety in the active site of the enzyme and this conformation was especially fixed by the hydrophobic interaction of the 2-alkoxy group with Leu515, Trp519, Val 566 and Ile572. It was concluded that the molecular volume and shape of the alkoxy moiety was a major factor in the inhibitory potency variation of the synthetic compounds.
- Sadeghian, Hamid,Seyedi, Seyed Mohammad,Attaran, Neda,Jabbari, Atena,Jafari, Zeinab
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experimental part
p. 238 - 244
(2011/11/12)
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- Rhodium-catalyzed one-pot hydroformylation-cyclization of allylbenzene derivatives: Simple and efficient route to 5,6-dihydronaphthalenes
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The one-pot hydroformylation-cyclization of allylbenzene derivatives by the catalyst system Rh(CO)2acac/ultranox626/CO/H2/CH2Cl2 led chemoselectively to 5,6-dihydronaphthalene derivatives 5a-d in good yields. The addition of a catalytic amount of H3PO4 enhanced in situ the cyclization process via the nucleophilic attack on the carbonyl group of the linear aldehyde, and finally the elimination of alcohol. The type of substitution on phenyl group of the allylbenzene is of great importance in enhancing the cyclization process.
- Alhaffar, Mouheddin,Suleiman, Rami,Ali, Bassam El
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experimental part
p. 778 - 782
(2010/07/06)
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- Efficient allyl to propenyl isomerization in functionally diverse compounds with a thermally modified Grubbs second-generation catalyst
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Heating compounds containing C-allylic appendages in MeOH in the presence of 10 mol % of Grubbs second-generation catalyst at 0.075 M substrate concentration leads to the corresponding 2-propenyl derivatives without further conjugation in the cases of ketones, esters, and lactams. The reaction is applicable to a large variety of functionally relevant terminal olefins, including O- and N-allyl ethers.
- Hanessian, Stephen,Giroux, Simon,Larsson, Andreas
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p. 5481 - 5484
(2007/10/03)
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- Bidentate ligands by self-assembly through hydrogen bonding: A general room temperature/ambient pressure regioselective hydroformylation of terminal alkenes
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The 6-DPPon (1)/rhodium catalyst allows for the first time a room temperature/ambient pressure regioselective hydroformylation of terminal alkenes with low catalyst loadings in good activity. The generality of this catalyst under these conditions was demonstrated for a wide range of structurally diverse alkenes equipped with many important functional groups. Thus, this practical and highly selective hydroformylation protocol, which omits the need for special pressure equipment, should find wide application in organic synthesis.
- Seiche, Wolfgang,Schuschkowski, Alexander,Breit, Bernhard
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p. 1488 - 1494
(2007/10/03)
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- The sulfonation of methyl and prenyl ethers of naturally occurring phenols with trimethylsilylchlorosulfonate as sulfonating agent
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At room temperature trimethylsilylchlorosulfonate has been found to be an effective and a mild reagent for the nuclear sulfonation of some methyl and prenyl ethers of naturally occurring phenols.
- Petit, Philippe,Bourgeois, Paul
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p. 194 - 195
(2007/10/03)
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- Monofluoro analogs of eugenol methyl ether as novel attractants for the oriental fruit fly
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Monofluoro analogs of eugenol methyl ether as potential attractants for the Oriental fruit fly (Bactrocera dorsalis, Hendel) were synthesized using selective fluorination reactions: electrophilic hydro- and iodofluorination, fluorodehydroxylation with (diethylamido)sulfur trifluoride (DAST), and Wittig fluoroolefination through the stabilized ylides. Unusual reduction of the double bond was detected in a reaction of eugenol methyl ether with pyridinium poly(hydrogen fluoride). Bis[(3,4-dimethoxyphenyl)alkyl] carbonates were identified as the novel nucleophilic substitution products of the intermediate generated from the reaction of 3,4-dimethoxybenzenealkanols with DAST. Reductive desulfonylation of fluorovinyl sulfone 24-(Z) with sodium amalgam afforded 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene (E/Z = 85: 15) which was highly attractive to the Oriental fruit fly.
- Khrimian,DeMilo,Waters,Liquido,Nicholson
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p. 8034 - 8039
(2007/10/02)
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- Studies on chromium trioxide-based oxidative coupling reagents and synthesis of lignan-cagayanone
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Oxidation of 1-arylprop-1-enes by using the reagent system CrO3-HClO4- CH3CN at 0-5°C gave seven products from methyl isoeugenol, five from ethyl isoeugenol, four from benzyl isoeugenol, and five from isosafrole. Cagayanone was obtained from isosafrole in one step. The structures of the products were elucidated and the mechanism of their formation is discussed.
- Kuo,Lin
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p. 1507 - 1512
(2007/10/02)
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