- Sterically hindered N-heterocyclic carbene/palladium(ii) catalyzed Suzuki-Miyaura coupling of nitrobenzenes
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Palladium-catalyzed denitrative Suzuki coupling of nitroarenes using 2-aryl-5-(2,4,6-triisopropylphenyl)-2,3-imidazolylidene[1,5-a]pyridines as the ligands is described. The key to success is the use of the NHC ligands which show strong donating ability and suitable steric hindrance allowing the successful oxidative addition of Ar-NO2 bonds. Both aromatic and aliphatic boronic acids are tolerated, and a variety of biphenyls and alkylarenes were obtained in good to excellent yields.
- Chen, Kai,Chen, Wei,Yi, Xiaofei,Chen, Wanzhi,Liu, Miaochang,Wu, Huayue
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supporting information
p. 9287 - 9290
(2019/08/08)
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- Selective synthesis of 2,6-triad dimethylnaphthalene isomers by disproportionation of 2-methylnaphthalene over mesoporous MCM-41
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2,6-Dimethylnaphthalene (2,6-DMN) is one of the crucial intermediates for the synthesis of polybutylenenaphthalate and polyethylene naphthalate (PEN). The complex synthesis procedure and the high cost of 2,6-DMN production significantly reduce the commercialisation of PEN even though PEN demonstrates superior properties compared with polyethylene terephthalate. 2,6-DMN can be produced by methylation of 2-methylnaphthalene (2-MN) and/or naphthalene, disproportionation of 2-MN, and/or isomerisation of dimethylnaphthalenes (DMNs). In this study, synthesis of 2,6-triad DMN isomers consisting of 2,6-DMN, 1,6-DMN, and 1,5-DMN have been investigated with the disproportionation of 2-MN over unmodified and Zr-modified mesoporous MCM-41 zeolite catalysts. In contrast to other DMN isomers, both 1,5-DMN and 1,6-DMN can be effectively isomerised to be profitable 2,6-DMN. The disproportionation of 2-MN experiments were carried out in a catalytic fixed-bed reactor in the presence of 1?g of catalyst at a temperature range of 350–500?°C and weight hourly space velocity between 1 to 3?h?1. The results demonstrated that mesoporous MCM-41 zeolite catalyst has a selective pore shape for 2,6-triad DMN isomers, which may allow a decrease in the production cost of 2,6-DMN. Additionally, 2,6-DMN was successfully synthesised by the disproportionation of 2-MN over MCM-41 zeolite catalyst. Furthermore, both the conversion of 2-MN and the selectivity of 2,6-DMN were considerably enhanced by the Zr impregnation on MCM-41.
- Güle?, Fatih,Niftaliyeva, Aysel,Karaduman, Ali
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p. 7205 - 7218
(2018/08/22)
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- Ni-Catalyzed cross-coupling of aryl thioethers with alkyl Grignard reagents via C-S bond cleavage
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A Ni-catalyzed cross-coupling of aryl thioethers with alkyl Grignard reagents, accompanied by the cleavage of the C(aryl)-SMe bond, has been presented. This method is distinguished by its mild conditions and moderate functional group tolerance, such as hydroxyl, halogen, and heterocycles, which should provide a straightforward access to the modification of sulfur-containing molecules.
- Zhu, Dan,Shi, Lei
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supporting information
p. 9313 - 9316
(2018/08/29)
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- Cross-coupling reaction with lithium methyltriolborate
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We newly developed lithium methyltriolborate as an air-stable white solid that is convenient to handle. The good performance of this triolborate for metal-catalyzed bond-forming reactions was demonstrated in palladium-catalyzed cross-coupling reactions wi
- Yamamoto, Yasunori,Ikizakura, Kazuya,Ito, Hajime,Miyaura, Norio
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p. 430 - 439
(2013/03/13)
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- Methylation of naphthalene on MTW-type zeolites. Influence of template origin and substitution of Al by Ga
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Two templates, methyltriethylammonium bromide (MTEA) and tetraethylammonium bromide (TEA) were used to synthesize aluminosilicate ZSM-12 zeolites. Additionally, zeolites isomorphously substituted (partially or totally) by gallium were prepared with MTEA.
- Wu, Wei,Wu, Weiguo,Kikhtyanin,Li, Lingfei,Toktarev,Ayupov,Khabibulin,Echevsky,Huang, Juan
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experimental part
p. 279 - 288
(2010/11/18)
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- Gold(I)-catalyzed double migration cascades toward (1E,3E)-dienes and naphthalenes
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A novel gold(I)-catalyzed cascade cycloisomerization of a variety of propargylic esters leading to unsymmetrically substituted naphthalenes has been developed. This domino process involves an unprecedented tandem sequence of 1,3- and 1,2-migrations of two
- Dudnik, Alexander S.,Schwier, Todd,Gevorgyan, Vladimir
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experimental part
p. 1859 - 1870
(2009/07/04)
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- Gold-catalyzed double migration-benzannulation cascade toward naphthalenes
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(Chemical Equation Presented) A novel gold(I)-catalyzed cycloisomerization of propargylic esters leading to unsymmetrically substituted naphthalenes has been developed. This cascade reaction involves an unprecedented tandem sequence of 1,3- and 1,2-migration of two different migrating groups. It is believed that this transformation likely proceeds via the formation of 1,3-diene intermediate or its precursor, which upon cyclization and aromatization steps transforms into the naphthalene core. 2008 American Chemical Society.
- Dudnik, Alexander S.,Schwier, Todd,Gevorgyan, Vladimir
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supporting information; experimental part
p. 1465 - 1468
(2009/04/10)
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- Indium-catalyzed asymmetric hydrogenation of unfunctionalized tetrasubstituted olefins
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(Chemical Equation Presented) Even notoriously unreactive substrates such as tetrasubstituted unfunctionalized olefins can be hydrogenated with high efficiency and excellent enantioselectivity using readily accessible chiral Ir catalysts. In this way, two adjacent stereogenic centers can be introduced in a single step (see scheme for an example; BArF = tetrakis(3,5- di(trifluoromethyl)-phenyl)borate, o-Tol = ortho-tolyl).
- Schrems, Marcus G.,Neumann, Eva,Pfaltz, Andreas
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p. 8274 - 8276
(2008/09/18)
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- Synthesis of annulated oxazolidinones as potential precursors of cyclic cis-β-amino alcohols
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A simple method for the synthesis of annulated 1,3-oxazolidin-2-ones from accessible ketones, acetylene, and carbon dioxide was developed. If their molecules contain arylalkyl substituents, intramolecular cyclization in acidic media gave rise to fused heterocyclic systems in high yields. The effects of the substituents in positions 3 and 5 of the oxazolidine ring on the regioselectivity of this cyclization were studied. The possibilities of converting oxazolidinones into cyclic cis-β-amino alcohols were studied.
- Chudinov,Gashev,Chernysheva,Semenov
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p. 123 - 136
(2007/10/03)
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- Rutheniun-catalyzed cycloisomerization of o-(ethynyl)phenylalkenes to diene derivatives via skeletal rearrangement
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Treatment of a series of 2′,2′-disubstituted (oethynyl)styrenes with TpRu(PPh3)(CH3CN)2PF6 (10 mol %) in benzene (80°C, 12-18 h) efficiently gave 2-alkenyl-1H-indene derivatives. This catalytic reaction represents an atypical enyne cycloisomerization with skeletal rearrangement of starting enyne, where the C=C bond is completely cleaved and inserted by the terminal alkynyl carbon. The reaction mechanism was elucidated by a series of deuterium and 13C labeling experiments, as well as by changing the substituents at the phenyl moieties. The mechanism is proposed to involve the following key steps: 5-endo-dig cyclization of ruthenium-vinylidene intermediate, a nonclassical ion formation, and the "methylenecyclopropane-trimethylenemethane" rearrangement.
- Madhushaw, Reniguntala J.,Lo, Ching-Yu,Hwang, Chun-Wei,Su, Ming-Der,Shen, Hung-Chin,Pal, Sitaram,Shaikh, Isak R.,Liu, Rai-Shung
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p. 15560 - 15565
(2007/10/03)
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- Efficient oxidative aromatization of 9,10-dihydroanthracenes with molecular oxygen catalyzed by ruthenium porphyrin complex
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In the presence of a catalytic amount of a ruthenium porphyrin complex, various 9,10-dihydroanthracene derivatives were aromatized with molecular oxygen to the corresponding anthracenes. It was found that the addition of sulfuric acid accelerated the aromatization at room temperature under atmospheric pressure of oxygen to afford various anthracenes in high yields.
- Tanaka, Hirotaka,Ikeno, Taketo,Yamada, Tohru
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p. 576 - 578
(2007/10/03)
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- Mechanistic studies of the palladium-catalyzed ring opening of oxabicyclic alkenes with dialkylzinc
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The mechanism of the palladium-catalyzed ring opening of oxabicyclic alkenes with dialkylzinc has been studied. Experiments which rule out a π-allyl mechanism were carried out. Trapping carbometalated products and synthesis and successful reaction of alkyl palladium species provided strong evidence in favor of an enantioselective carbopalladation as the key step in the mechanism. The studies also suggest that a cationic palladium species is responsible for carbopalladation of the alkene. The combination of palladium and dialkylzinc is unique in that the dialkylzinc functions both in the transmetalation to palladium and as a Lewis acid in forming the reactive cationic palladium species.
- Lautens,Hiebert,Renaud
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p. 6834 - 6839
(2007/10/03)
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- Characterization of the combustion products of polyethylene
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Polyethylene (PE) was burned in a tube-type furnace with an air flow at a temperature of 600~900°C. Combustion products were collected with glass wool, glass fiber filter, and XAD-2 adsorbent. The analysis of the products was performed with GC-FID and GC-MSD. At low temperature, hydrocarbons were the major components, while at higher temperature the products were composed of polycyclic aromatic hydrocarbons. With the high performance of the Hewlett-Packard 6890GC-5973MSD, more compounds were identified in comparison with previous studies.
- Piao, Mingjun,Chu, Shaogang,Zheng, Minghui,Xu, Xiaobai
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p. 1497 - 1512
(2007/10/03)
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- Studies in catalytic dehydrogenation: Part X1 - Syntheses of alkylsubstituted spirol[4,6]undecanes and dehydrogenation of 1 -ethyl-8,9- benzospiro[4,6]undecane
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Acylation of benzene with 2-alkylsubstituted cyclopentan-l,l-diacetic anhydrides gives the keto acids (2, R = Me, Et, Prn, Pri) which are converted into the desired alkylsubstituted spiro[4,6]undecanes 5 by Paar hydrogenation followed by cyclisation and Wolff-Kishner reduction. Catalytic dehydrogenation of l-ethyl-8,9-benzospiro[4,6]undecane 5b with Pd-C gives a complex mixture of products from which a few major products like naphthalene, 2-methylnaphthalene, l-ethylnaphthalene, 1,2-dimethylnaphthalene, 1,4,6-trimethylnaphthalene, anthracene and l-methylanthracene are identified by comparative GC-mass spectra. A plausible explanation of the formation of these products is suggested.
- Lahiri, Sikha,Pal, Panchanan,Chatterjee, Gautam,Maity, Basudev,Sen
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p. 768 - 773
(2007/10/03)
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- W(CO)6-Mediated Desulfurdimerization of Dithioketals. Evidence for a Thione Intermediate
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Upon treatment with W(CO)6, dithioketals undergo desulfurdimerization to give the corresponding dimeric olefins in good to excellent yields.The mechanism of this the newly discovered reaction has been investigated.Thioketones have been isolated from the reactions of highly crowded dithioketals.The mechanism for the formation of thioketones has been shown to occur via a new type of radical fragmentation process of dithiolane.Thermolysis of 2,2-dimethylindan-1-yl 2-thiophenoxyethyl sulfide in the presence of tert-butyl adamantane-1-peroxycarboxylate (a typical radical initiator) has been studied for comparison.Thioketones react with W(CO)6, giving dimeric olefins and/or undergoing carbene-like insertion reactions.
- Yeung, Lam Lung,Yip, Yu Chi,Luh, Tien-Yau
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p. 1874 - 1881
(2007/10/02)
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- Thiophenes as Traps for Benzyne. 2. Cycloadditions and Ene Reactions
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The reactions of 11 mono- and disubstituted thiophenes (1b-1l) with benzyne generated from diphenyliodonium 2-carboxylate (7) were studied under a standard set of conditions.The major products were naphthalenes (3) whose substitution patterns indicated that both and cycloaddition occurred, with the former predominating.A significant proportion of cycloaddition was found only with the 3-halothiophenes 1i and 1k, suggesting enamine-like enhancement of the 2?-character of the thiophene.Benzothiophenes (8) were found in low yields in several of the reactions, and their substitution patterns suggested a cycloaddition mechanism involving an intermediate betaine 11.Ene (17) and especially double ene (18) products were observed with the alkylthiophenes 1b-d and 1g.The halothiophenes 1h-l underwent substantial carbon-halogen bond cleavage leading to halogenated phenylthiophenes.
- Reinecke, Manfred G.,Mazza, Dario Del
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p. 2142 - 2146
(2007/10/02)
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- INTRODUCTION OF METHYL GROUPS INTO POLYCYCLIC COMPOUNDS THROUGH THE PHOSPHONIUM SALTS OF METHYLNAPHTHALENE AND 9-METHYLPHENANTHRENE
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Chloromethyl derivatives synthesized by the chloromethylation of naphthalene and methylnaphthalenes were converted into the corresponding triphenylphosphonium salts.Alkaline hydrolysis of the latter gave 1-methylnaphthalene and some di-, tri-, and tetramethylnaphthalenes. 9-Methylphenanthrene was obtained similarly from phenanthrene.The corresponding diarylethenes were synthesized from the phosphonium salts by the Wittig reaction.
- Listvan, V. N.,Stasyuk, A. P.
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p. 354 - 359
(2007/10/02)
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- Sulfonation of aromatic compounds in the presence of solvents
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A process for the sulfonation of aromatic compounds wherein an aromatic substance consisting of one or more aromatic compounds susceptible to the action of sulfur trioxide is formed into a reactant by admixture with one or more organic liquids, substantially inert to sulfur trioxide under the conditions of the process, which reactant is brought to boiling at a temperature not greater than 100° C under a pressure of from 0.1 mm Hg to atmospheric pressure, gaseous sulfur trioxide is introduced thereinto thereby causing it to continue to boil, the component or components of the reactant thus volatilized is or are reconverted to liquid in a heat-exchanger and recycled to the reaction chamber, and the pressure in the reaction chamber and the rate at which the gaseous sulfur trioxide is introduced into the reactant are controlled so as to ensure that there is always present in the reaction chamber an amount of volatilizable matter exceeding that amount volatilizable by the heat of reaction of the aromatic substance present in the reaction chamber with the gaseous sulfur trioxide in contact with said aromatic substance and that the temperature of the reaction mixture is a temperature of 100° C or below.
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