- Application of complementary mass spectrometric techniques to the identification of ketoprofen phototransformation products
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Ketoprofen (KP) is a nonsteroidal anti-inflammatory drug, which during UV irradiation rapidly transforms into benzophenone derivatives. Such transformation products may occur after topical application of KP, which is then exposed to sunlight resulting in a photo-allergic reaction. These reactions are mediated by the benzophenone moiety independently of the amount of allergen. The same reactions will also occur during wastewater or drinking water treatment albeit their effect in the aqueous environment is yet to be ascertained. In addition, only a few such transformation products have been recognised. To enable the detection and structural elucidation of the widest range of KP transformation products, this study applies complementary chromatographic and mass spectrometric techniques including gas chromatography coupled to single quadrupole or ion trap mass spectrometry and liquid chromatography hyphenated with quadrupole-time-of-flight mass spectrometry. Based on structural information gained in tandem and multiple MS experiments, and on highly accurate molecular mass measurements, chemical structures of 22 transformation products are proposed and used to construct an overall breakdown pathway. Among the identified transformation products all but two compounds retained the benzophenone moietya€"a result, which raises important issues concerning the possible toxic synergistic effects of KP and its transformation products. These findings trigger further research into water treatment technologies that would limit their entrance into environmental or drinking waters. Copyright
- Kosjek, Tina,Perko, Silva,Heath, Ester,Kralj, Bogdan,Zigon, Dusan
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Read Online
- Contrastive photoreduction pathways of benzophenones governed by regiospecific deprotonation of imidazoline radical cations and additive effects
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In the photoreaction of benzophenones with 1,3-dimethyl-2- phenylbenzimidazoline (DMPBI), benzhydrols were major products. Addition of H2O accelerated the reaction with no change in the product distribution, while AcOH, PhOH, and metal salts such as LiClO4 and Mg(ClO4)2 were effective additives to produce benzpinacols. In contrast, benzpinacols were exclusively formed regardless of the solvent and the additive in the reactions with 2-(o-hydroxyphenyl)-1,3- dimethylbenzimidazoline (o-HPDMBI). These observations are consistent with the hypothesis that DMPBI.+ donates a proton at the C2 position to the benzophenone ketyl radicals while o-HPDMBI.+ donates a phenol proton.
- Hasegawa, Eietsu,Seida, Takayuki,Chiba, Naoki,Takahashi, Tomoya,Ikeda, Hiroshi
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- Chemistry and stereochemistry of benzyl-benzyl interactions in MH+ ions of dibenzyl esters upon chemical ionization and collision-induced dissociation conditions
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Isobutane chemical ionization mass spectra of dibenzyl esters of a wide variety of aliphatic, olefinic, alicyclic and aromatic dicarboxylic acids exhibit abundant m/z 181 C14H13+ ions, indicating a highly general rearrangement process involving the formation of a new bond between the two benzyl groups. An extensive collision-induced dissociation and deuterium labeling study suggested that these ions are an almost equimolar mixture of isomeric α-o-tolylbenzyl, α-p-tolylbenzyl and p-benzylbenzyl cation structures, and this composition is identical for all the diesters examined. This structural assignment of the C14H13 ions suggests a mechanistic pathway for their generation, based on the formation of the new bond between the benzyl methylene group of the protonated benzoxycarbonyl and the phenyl ring of the other ester moiety via π- (and/or ion-neutral) and α-complexes. Stereoisomeric diesters show an unusual steric effect: trans-isomers give rise to much more abundant C14H13+ ions than the cis counterparts. This behavior is explained by stabilized proton-bridged structures of the MH+ ions of the cis-isomers.
- Edelson-Averbukh,Mandelbaum
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Read Online
- Experimental and density functional theory studies on hydroxymethylation of phenylboronic acids with paraformaldehyde over a Rh-PPh3 catalyst
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The synthesis of benzyl alcohols (BAs) is highly vital for their wide applications in organic synthesis and pharmaceuticals. Herein, BAs was efficiently synthesized via hydroxymethylation of phenylboronic acids (PBAs) and paraformaldehyde over a simple Rh-PPh3 catalyst combined with an inorganic base (NaOH). A variety of BAs with the groups of CH3?, CH3O?, Cl?, Br?, and so on were obtained with moderate to good yields, indicating that the protocol had a good universality. Density functional theory (DFT) calculations proposed the Hayashi-type arylation mechanism involved the arylation step of PBA and Rh(OH)(PPh3)2 catalyst to form Rh(I)-bound aryl intermediates and the hydrolysis step of Rh(I)-bound aryl intermediates and HCHO to generate BA product (the rate-determining step). The present route provides a valuable and direct method for the synthesis of BAs and expands the application range of paraformaldehyde.
- Wang, Kuan,Lan, Jie,He, Zhen-Hong,Cao, Zhe,Wang, Weitao,Yang, Yang,Liu, Zhao-Tie
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- I-Pr2NMgCl·LiCl Enables the Synthesis of Ketones by Direct Addition of Grignard Reagents to Carboxylate Anions
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The direct preparation of ketones from carboxylate anions is greatly limited by the required use of organolithium reagents or activated acyl sources that need to be independently prepared. Herein, a specific magnesium amide additive is used to activate and control the addition of more tolerant Grignard reagents to carboxylate anions. This strategy enables the modular synthesis of ketones from CO2 and the preparation of isotopically labeled pharmaceutical building blocks in a single operation.
- Colas, Kilian,Dos Santos, A. Catarina V. D.,Mendoza, Abraham
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supporting information
(2019/10/08)
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- Nickel Catalyzed Intermolecular Carbonyl Addition of Aryl Halide
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In this study, we develop a nickel-catalyzed carbonyl arylation reaction employing aldehydes with aryl and allyl halides. Various aryl, α,β-unsaturated aldehyde and aliphatic aldehydes can be converted into their corresponding secondary alcohols in moderate-to-high yields. In addition, we extended this approach to develop an asymmetric reductive coupling reaction that combines nickel salts with chiral bisoxazoline ligands to give secondary alcohols with moderate enantioselectivity.
- Ishida, Seima,Suzuki, Hiroyuki,Uchida, Seiichiro,Yamaguchi, Eiji,Itoh, Akichika
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supporting information
p. 7483 - 7487
(2019/12/11)
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- CoI-Catalyzed Barbier Reactions of Aromatic Halides with Aromatic Aldehydes and Imines
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The reductive Barbier coupling of aromatic halides and electrophiles has been achieved using a CoBr2/1,10-phenanthroline catalytic system and over stoichiometric amounts of zinc. The reaction displayed a broad scope of substrates, including (hetero)aryl chlorides as pro-nucleophiles and aldehydes or imines as electrophiles, leading to diarylmethanols and diarylmethylamines in moderate to excellent yields, respectively.
- Presset, Marc,Paul, Jér?me,Cherif, Ghania Nait,Ratnam, Nisanthan,Laloi, Nicolas,Léonel, Eric,Gosmini, Corinne,Le Gall, Erwan
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supporting information
p. 4491 - 4495
(2019/02/27)
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- 4-Methyltetrahydropyran (4-MeTHP): Application as an Organic Reaction Solvent
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4-Methyltetrahydropyran (4-MeTHP) is a hydrophobic cyclic ether with potential for industrial applications. We herein report, for the first time, a comprehensive study on the performance of 4-MeTHP as an organic reaction solvent. Its broad application to organic reactions includes radical, Grignard, Wittig, organometallic, halogen-metal exchange, reduction, oxidation, epoxidation, amidation, esterification, metathesis, and other miscellaneous organic reactions. This breadth suggests 4-MeTHP can serve as a substitute for conventional ethers and harmful halogenated solvents. However, 4-MeTHP was found incompatible with strong Lewis acids, and the C?O bond was readily cleaved by treatment with BBr3. Moreover, the radical-based degradation pathways of 4-MeTHP, THP and 2-MeTHF were elucidated on the basis of GC-MS analyses. The data reported herein is anticipated to be useful for a broad range of synthetic chemists, especially industrial process chemists, when selecting the reaction solvent with green chemistry perspectives.
- Kobayashi, Shoji,Tamura, Tomoki,Yoshimoto, Saki,Kawakami, Takashi,Masuyama, Araki
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p. 3921 - 3937
(2019/11/11)
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- Base-Promoted Aerobic Oxidation/Homolytic Aromatic Substitution Cascade toward the Synthesis of Phenanthridines
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The current protocol represents a transition metal-free synthesis of polysubstituted phenanthridines from abundant starting materials like benzhydrol and 2-iodoaniline derivatives. The reaction involves sequential oxidation of alcohol and direct condensation reaction with the amine resulting in a C?N bond formation followed by a radical C?C coupling in a cascade sequence. The used base potassium tert-butoxide plays a dual role in dehydrogenation and homolytic aromatic substitution reaction. Using this methodology, twenty substituted phenanthridine derivatives were synthesized with up to 85% isolated yield. (Figure presented.).
- Maiti, Debabrata,Halder, Atreyee,De Sarkar, Suman
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supporting information
p. 4941 - 4948
(2019/11/03)
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- Synthesis and biological evaluation of new N-substituted 4-(arylmethoxy)piperidines as dopamine transporter inhibitors
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The library of new N-substituted 4-(arylmethoxy)piperidines as dopamine transporter inhibitors was designed and synthesized. H-Bond donors in piperidine ring were found to be important for reduced locomotor activity in mice. 4-[Bis(4-fluorophenyl)methoxy]piperidine has IC50 17.0 ± 1.0 nm for dopamine transporter and locomotor activity, which is lower than that for cocaine.
- Lapa, Gennady B.,Lapa, Alla A.
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p. 203 - 205
(2019/04/25)
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- The carbonyl group tuned electron-deficient phosphorus ligands and their application in Rhodium catalyzed arylation to aldehydes
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Acylphosphines, which could be efficiently prepared from acid chlorides and secondary phosphines, were developed as a type of carbonyl group tuned electron-deficient phosphorus ligand. They were found to be a kind of efficient ligand in Rhodium catalyzed arylation to aldehydes through accelerating the transmetalation process. Chiral acylphosphine ligands could be generated from carboxylic acids bearing the chiral framework correspondingly.
- Yang, Jiefang,Chen, Xingyu,Wang, Zhiqian
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supporting information
p. 5673 - 5675
(2015/09/15)
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- Electronic effects on the substitution reactions of benzhydrols and fluorenyl alcohols. Determination of mechanism and effects of antiaromaticity
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A range of substituted benzhydrols and fluorenols were prepared and subjected to acid catalysed methanolysis. Analysis of the rates of each of these processes showed correlation with Hammett σ+ parameters as is consistent with the significant build-up of positive charge adjacent to the ring. In combination with the similarity of the electronic susceptibility of the processes, these data suggest that both reactions proceed through a unimolecular rate-determining step. This shows that the effect of fusion of the phenyl systems (and hence potentially introducing an antiaromatic carbocation intermediate) is only to slow the rate of reaction rather than change the mechanism of the process.
- George, Stephen R. D.,Elton, Timothy E.,Harper, Jason B.
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supporting information
p. 10745 - 10750
(2015/11/17)
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- Rhodium-catalyzed arylation of acylsilanes with sodium tetraarylborates
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Rhodium(I)-catalyzed arylation of benzoylsilanes with sodium tetraarylborates affords α-silyl benzhydrols, benzhydryl silyl ethers, benzhydrols, and diaryl ketones selectively depending on the catalyst, solvent, and temperature.
- Matsuda, Takanori,Mizuno, Kohei,Watanuki, Shoichi
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supporting information
p. 64 - 67
(2014/06/09)
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- One-pot synthesis of indene derivatives by CF3SO 3H-promoted reactions of benzylic alcohols and 1,3-dicarbonyl compounds
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An efficient and convenient one-pot synthesis of indene derivatives was achieved in moderate to high yields by the CF3SO3H promoted coupling/cyclization reaction of benzylic alcohols and 1,3-dicarbonyls for the first time. For the reactions of methoxy- or methyl-substituted diarylmethanols with 1,3-dicarbonyls, 2 equiv of CF3SO3H was needed to reach the best results; but for the reactions of methoxy-substituted arylethanols with 1,3-dicarbonyls, 0.6 equiv of CF 3SO3H at lower temperatures was capable of promoting the reaction finished.
- Zhang, Wei,Zhang, Wenxue,Dai, Yisi,Zhu, Haizhen
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supporting information
p. 1747 - 1750
(2013/03/28)
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- Direct electrosynthesis of ketones from benzylic methylenes by electrooxidative C-H activation
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Electrify your chemistry! Direct electrosynthesis of ketones from benzylic methylenes in an undivided cell was realized in moderate to good yields (see scheme). In this electrosynthesis, electrons instead of conventional oxidants and catalysts are employed to make the reaction environmentally benign. Moreover, the reaction intermediate radical was detected by ESR spectroscopy and the reaction mechanism was clarified.
- Meng, Li,Su, Jihu,Zha, Zhenggen,Zhang, Li,Zhang, Zhenlei,Wang, Zhiyong
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supporting information
p. 5542 - 5545
(2013/05/23)
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- Lewis base activation of Lewis acids: Group 13. in situ generation and reaction of borenium ions
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A variety of Lewis bases were combined with 9-BBN-NTf2 to establish the requirements for the generation of borenium cations. Five different types of behaviors were found, but the most interesting was the combination of Et3N, DABCO, 2,6-lutidine, or Ph3P=S, which formed borenium ions exclusively even in sub- or superstoichiometric quantities. The 9-BBN borenium ion complex of 2,6-lutidine rapidly catalyzes the hydrosilylation of a variety of ketones in the presence of Et3SiH. Preliminary mechanistic experiments suggest that the reduction involves borenium ion activation of Et3SiH and not the ketone.
- Denmark, Scott E.,Ueki, Yusuke
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supporting information
p. 6631 - 6634
(2014/01/06)
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- Synthesis of fluorenone derivatives through Pd-catalyzed dehydrogenative cyclization
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Palladium-catalyzed dual C-H functionalization of benzophenones to form fluorenones by oxidative dehydrogenative cyclization is reported. This method provides a concise and effective route toward the synthesis of fluorenone derivatives, which shows outstanding functional group compatibility.
- Li, Hu,Zhu, Ru-Yi,Shi, Wen-Juan,He, Ke-Han,Shi, Zhang-Jie
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supporting information
p. 4850 - 4853,4
(2012/12/12)
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- Continuous preparation of arylmagnesium reagents in flow with inline IR monitoring
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A newly developed microscale ReactIR flow cell was used as a convenient and versatile inline analytical tool for Grignard formation in continuous flow chemical processing. The LiCl-mediated halogen/Mg exchange reaction was used for the preparation of functionalized arylmagnesium compounds from aryl iodides or bromides. Furthermore, inline IR monitoring was used for the analysis of conversion and possible byproduct formation, as well as a potential tool for elucidation of mechanistic details. The results described herein indicate that the continuous flow systems are effective for highly exothermic reactions such as the Grignard exchange reaction due to fast mixing and efficient heat transfer.
- Brodmann, Tobias,Koos, Peter,Metzger, Albrecht,Knochel, Paul,Ley, Steven V.
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experimental part
p. 1102 - 1113
(2012/08/27)
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- The arylation of aldehydes with arylboronic acids using metal-organic framework Ni(HBTC)BPY as an efficient heterogeneous catalyst
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A highly crystalline porous Ni(HBTC)BPY was synthesized from the reaction of 1,3,5-benzenetricarboxylic acid, nickel nitrate hexahydrate, and 4,4′-bipyridine by a solvothermal method. Physical characterizations of the solid catalyst were achieved by using several techniques, including X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. The Ni(HBTC)BPY exhibited high catalytic activity in the arylation of aldehydes with arylboronic acids to form diarylmethanols. The catalyst could be separated from the reaction mixture by simple filtration or centrifugation, and could be reused without a significant degradation in catalytic activity. No contribution from homogeneous catalysis of active species leaching into the liquid phase was detected.
- Phan, Nam T.S.,Nguyen, Tung T.,Ta, Anh H.
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- Kinetic resolution of diarylmethanols using a mutated variant of lipase CALB
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An enzymatic kinetic resolution of diarylmethanols via acylation has been developed. This was achieved by the use of a mutated variant of CALB that accepts larger substrates compared to the wild type. By the use of diarylmethanols with two differently sized aryl groups, enantioselective transformations were achieved. A larger size-difference led to a higher enantioselectivity. In addition, substrates with electronically different aryl groups, such as phenyl and pyridyl, also gave an enantioselective reaction. The highest E value was observed with a substrate where steric and electronic effects were combined.
- Engstr?m, Karin,Vallin, Michaela,Hult, Karl,B?ckvall, Jan-E.
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body text
p. 7613 - 7618
(2012/09/07)
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- Microwave-assisted nickel(II) acetylacetonate-catalyzed arylation of aldehydes with arylboronic acids
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Applying sealed vessel microwave heating at 180 °C in toluene the arylation of aromatic and aliphatic aldehydes with arylboronic acids using 1-2 mol % of Ni(acac)2 as a catalyst can be performed efficiently within 10-30 min providing the desired diarylmethanols or benzyl alcohols in good yields.
- Chen, Wen,Baghbanzadeh, Mostafa,Kappe, C. Oliver
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experimental part
p. 1677 - 1679
(2011/04/25)
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- Chiral 1,1′-binaphthylazepine-derived amino alcohol catalyzed asymmetric aryl transfer reactions with boroxine as aryl source
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Using chiral 1,1′-binaphthylazepine-derived amino alcohol as catalyst, the direct addition of in situ prepared arylzinc (with triphenylboroxine as aryl source) to various aryl aldehydes can afford optically active diarylmethanols in high yields and enantioselectivities (up to 96%).
- Liu, Can,Guo, Zong-Liang,Weng, Jiang,Lu, Gui,Chan, Albert S. C.
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experimental part
p. 159 - 164
(2010/09/04)
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- Highly efficient and facile aryl transfer to aldehydes using ArB(OH) 2-GaMe3
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A rapid and efficient procedure for the synthesis of diarylmethanols has successfully been achieved by the aryl transfer to aldehydes using the ArB(OH)2-GaMe3 combined systems in excellent yields (up to 98%) at room temperature. Georg Thieme Verlag Stuttgart.
- Jia, Xuefeng,Fang, Ling,Lin, Aijun,Pan, Yi,Zhu, Chengjian
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body text
p. 495 - 499
(2009/09/08)
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- Sp-sp3 C-C bond formation via Fe(OTf)3/TfOH cocatalyzed coupling reaction of terminal alkynes with benzylic alcohols
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An Fe(OTf)3/TfOH cocatalyzed sp-sp3 C-C bond formation through the coupling of benzylic alcohols with terminal alkynes in the absence of base has been developed. H2O is the sole by-product.
- Xiang, Shi-Kai,Zhang, Li-He,Jiao, Ning
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supporting information; experimental part
p. 6487 - 6489
(2010/03/04)
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- Method for Asymmetric Hydrosilylation of Ketones
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Method of asymmetrically hydrosilylating substrates using catalysts having a ligand of the compound of the formula (I) wherein R is optionally substituted alkyl, cycloalkyl, aryl or heteroaryl;R′ is hydrogen, optionally substituted lower alkyl; andR″ is hydrogen, halogen, optionally substituted alkyl, hydroxy, amino (e.g., primary, secondary or tertiary), alkenyl; or an enantiomer thereof; or an enantiomeric mixture thereof with a transition metal. Particularly suitable reactions include the asymmetric hydrosilylation of ketones.
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Page/Page column 6
(2008/12/04)
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- Development of asymmetric nickel-catalyzed arylation of aromatic aldehydes with arylboron reagents
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The development of the nickel-catalyzed 1,2-addition of triarylboroxins to aromatic aldehydes in the presence of a phosphine ligand is described. This development allowed the asymmetric nickel-catalyzed 1,2-addition of arylboron reagents to aromatic aldehydes. The enantioselectivity is synthetically acceptable (up to 81 % ee) using 1-naphthaldehyde and 2-substituted aromatic aldehydes as substrates. The results have enantioselectivity comparable to the best results reported by us for the rhodium-catalyzed arylation of aromatic aldehydes. Georg Thieme Verlag Stuttgart · New York.
- Yamamoto, Kana,Tsurumi, Kaori,Sakurai, Fumie,Kondo, Kazuhiro,Aoyama, Toyohiko
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experimental part
p. 3585 - 3590
(2009/06/18)
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- Nickel-catalyzed 1,2-addition of arylboroxines to aromatic aldehydes
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Development of Ni-Et-Duphos-catalyzed 1,2-addition of arylboroxines to aromatic aldehydes is described. The dramatic effect of boron reagent and phosphine ligand is observed. This method with a phosphine ligand allows asymmetric arylation of aromatic aldehydes (up to 78% ee).
- Arao, Takafumi,Kondo, Kazuhiro,Aoyama, Toyohiko
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p. 4115 - 4117
(2008/02/03)
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- Asymmetric synthesis of diarylmethanols: Development of a hemilabile phosphorus ligand based on the concept of conformational control
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The asymmetric synthesis of diarylmethanols using a new hemilabile phosphorus ligand based on the concept of conformational control is described. Georg Thieme Verlag Stuttgart.
- Arao, Takafumi,Suzuki, Kiyoto,Kondo, Kazuhiro,Aoyama, Toyohiko
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p. 3809 - 3814
(2008/02/09)
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- Photoinduced electron-transfer systems consisting of electron-donating pyrenes or anthracenes and benzimidazolines for reductive transformation of carbonyl compounds
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Photoinduced electron-transfer reactions of several ketone substrates were studied to evaluate the utilities of 1,6-bis(dimethylamino)pyrene (BDMAP), 1,6-dimethoxypyrene (DMP), 9,10-bis(dimethylamino)anthracene (BDMAA), and 9,10-dimethoxyanthracene (DMA) as electron-donating sensitizers cooperating with 2-aryl-1,3-dimethylbenzimidazolines. BDMAP and DMP generally led higher conversion of ketones and better yield of reduction products compared to BDMAA and DMA.
- Hasegawa, Eietsu,Takizawa, Shinya,Seida, Takayuki,Yamaguchi, Akira,Yamaguchi, Naoto,Chiba, Naoki,Takahashi, Tomoya,Ikeda, Hiroshi,Akiyama, Kimio
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p. 6581 - 6588
(2007/10/03)
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- The synthesis and biological evaluation of dopamine transporter inhibiting activity of substituted diphenylmethoxypiperidines
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The synthesis of potent 4-aryl methoxypiperidinol inhibitors of the dopamine transporter is described. Symmetrical para substituents of the benzene rings are important for high potency in binding to the dopamine transporter. 4-[Bis(4-fluorophenyl) methoxy]-1-methylpiperidine has an IC50 of 22.1 ± 5.73 nM and increases locomotor activity in mice.
- Lapa, Gennady B.,Byrd, Gary D.,Lapa, Alla A.,Budygin, Evgeny A.,Childers, Steven R.,Jones, Sara R.,Harp, Jill J.
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p. 4915 - 4918
(2007/10/03)
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- Beyond U0126. Dianion chemistry leading to the rapid synthesis of a series of potent MEK inhibitors
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Employing phenylmalonitrile dianion chemistry, a large number of analogues of MEK inhibitor lead SH053 (IC50=140 nM) were rapidly synthesized leading to single digit nM inhibitors, displaying submicromolar AP-1 transcription inhibition in COS-7 cells. Compound 41, exhibiting a MEK IC 50=12 nM showed ip activity in a TPA-induced ear edema model with an ED50=5 mg/kg.
- Wityak, John,Hobbs, Frank W.,Gardner, Daniel S.,Santella III, Joseph B.,Petraitis, Joseph J.,Sun, Jung-Hui,Favata, Margaret F.,Daulerio, Andrea J.,Horiuchi, Kurumi Y.,Copeland, Robert A.,Scherle, Peggy A.,Jaffe, Bruce D.,Trzaskos, James M.,Magolda, Ronald L.,Trainor, George L.,Duncia, John V.
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p. 1483 - 1486
(2007/10/03)
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- Structural changes in concentrated solutions of alkali metal monosubstituted benzophenone radical anions as deduced front1H NMR measurements
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The radical anions of monosubstituted benzophenones (including 2-, 3- and 4-methyl-, 4-tert-butyl- and 4-phenylbenzophenone) with lithium, sodium and potassium as countercations in tetrahydrofuran (THF) were studied by paramagnetic solvent 1H NMR shift measurements in the concentration range ca 0.1-1.0 M. In addition to the cation effects, marked positional isomer and substituent effects were found for (1) molar paramagnetism, (2) magnetic state, (3) solubility, (4) structural stability with respect to concentration or addition of cosolvents and (5) rapidity of attainment of their equilibrium structure. The major conclusions which can be drawn are (a) the solvation behavior of the countercation is governed by the anion, (b) an alkyl group in the 4-position makes the structure of the lithium and sodium monosubstituted benzophenone radical anions concentration dependent and (c) in most cases, alkali metal aromatic ketone radical anions generated by electron transfer from the corresponding naphthalene radical anion attain their equilibrium structure rapidly. The data are interpreted on the basis of the involvement of spin-triplet interactions within 'dimers' or higher clusters. Copyright
- Micha-Screttas, Maria,Heropoulos, Georgios A.,Steele, Barry R.
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p. 586 - 592
(2007/10/03)
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- Arene-catalysed lithiation of fluoroarenes
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The reaction of different fluoroarenes 1 with lithium and a catalytic amount (7%) of naphthalene in THF at -30°C affords the corresponding aryllithium intermediates which, by reaction with several electrophiles at temperatures ranging between -30 and 0°C, lead to the expected products 2, after hydrolysis. (C) 2000 Elsevier Science Ltd.
- Guijarro, David,Yus, Miguel
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p. 1135 - 1138
(2007/10/03)
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- CoMFA study of novel phenyl ring-substituted 3α- (diphenylmethoxy)tropane analogues at the dopamine transporter
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A series of phenyl ring-substituted analogues of 3α- (diphenylmethoxy)tropane (benztropine) has been prepared as novel probes for the dopamine transporter. Cross-validated comparative molecular field analysis (CoMFA) models of the binding domain on the do
- Newman, Amy Hauck,Izenwasser, Sari,Robarge, Michael J.,Kline, Richard H.
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p. 3502 - 3509
(2007/10/03)
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- Benzylphosphonic acid inhibitors of human prostatic acid phosphatase
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A series of α-substituted benzylphosphonic acids is described as inhibitors of human prostatic acid phosphatase, an enzyme has been used as a model to study aryl phosphatases. The most potent inhibitors in this series are 2-trifluoromethylbenzhydrylphosphonic acid (9 μM), and α-(2-phenylethyl)benzylphosphonic acid (14 μM). The structure-activity studies suggest that bulk tolerance beyond the phosphate binding area limits the steric or hydrophobic contribution to inhibitor potency achieved through α-carbon substitution.
- Schwender,Beers,Malloy,Cinicola,Wustrow,Demarest,Jordan
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p. 311 - 314
(2007/10/03)
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- Phosphorus Lone Pairs Stabilization of Carbocations: the Synthesis and Dynamics of Unsymmetrical Methylene Phosphonium Ions
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Halide abstractions from P-chlorinated phosphorus ylides 9a-c either by AlCl3 or SnCl2 yield unsymmetrical methylene phosphonium ions 10a-c in which energy barriers > 83 kJ mol-1 for the rotation around the P=C have been estimated by NMR techniques.The salts with AlCl4- counteranions are stable, but compounds with SnCl3- anions decompose stereoselectively to unsymmetrical methylene phosphanes, SnCl2, and t-BuCl.
- Heim, Udo,Pritzkow, Hans,Schoenberg, Hartmut,Gruetzmacher, Hansjoerg
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p. 673 - 674
(2007/10/02)
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- Comparative Mechanistic Study of the Reaction of Benzophenone with n-BuMgBr and n-BuLi
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Substituent effects on reactivity and product distribution (addition vs reduction) were determined for the reactions of benzophenones with n-BuMgBr and n-BuLi at 0 deg C.In case of the reaction with n-BuMgBr, meta and para-substituted benzophenones gave a reasonably linear Hammet plot, from which the ρ value of 1.45 was calculated, while ortho-substituted derivatives deviated downward from the correlation line.In contrast, the reaction with n-BuLi exhibit very small substituent effects on reactivity.The product distrubution is highly dependent on substituents in the n-BuMgBr reaction, whereas it is essentially independent of substituents in the n-BuLi reaction.Mechanistic differences between the reactions of these two reagents are discussed on the basis of these experimental results.
- Yamataka, Hiroshi,Miyano, Nobutaka,Hanafusa, Terukiyo
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p. 2573 - 2575
(2007/10/02)
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- Oxidation of Diphenylmethanol by Bromamine T. A Kinetic and Mechanistic Study
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Bromamine T (BAT) oxidises diphenylmethanol and substituted diphenylmethanols smoothly and quantitatively to the respective benzophenones in aquoeus acetic acid.Mineral acids catalyse the reaction and the rate law is found to be -d/dt=k+>.The reaction is characterised by the absence of any kinetic isotope effect and a break in the Hammett plot with ρ values of -4.2 and -0.4 for the two limbs.Three alternative mechanistic pathways have been proposed involving (i) diphenylmethyl cation, (ii) a 'phenonium ion' type intermediate from the decomposition of the alkyl hydrobromite ester, or (iii) ipso substitution at the benzene ring followed by dehydrobromination and aromatization.
- Gunasekaran, Somasundaram,Venkatasubramanian, Nagaswami
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p. 949 - 954
(2007/10/02)
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