- Transition-Metal-Free Suzuki-Type Cross-Coupling Reaction of Benzyl Halides and Boronic Acids via 1,2-Metalate Shift
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Cross-coupling of organoboron compounds with electrophiles (Suzuki-Miyaura reaction) has greatly advanced C-C bond formation and has been well received in medicinal chemistry. During the past 50 years, transition metals have played a central role throughout the catalytic cycle of this important transformation. In this process, chemoselectivity among multiple carbon-halogen bonds is a common challenge. In particular, selective oxidative addition of transition metals to alkyl halides rather than aryl halides is difficult due to unfavorable transition states and bond strengths. We describe a new approach that uses a single organic sulfide catalyst to activate both C(sp3) halides and arylboronic acids via a zwitterionic boron "ate" intermediate. This "ate" species undergoes a 1,2-metalate shift to afford Suzuki coupling products using benzyl chlorides and arylboronic acids. Various diaryl methane analogues can be prepared, including those with complex and biologically active motifs. The reactions proceed under transition-metal-free conditions, and C(sp2) halides, including aryl bromides and iodides, are unaffected. The orthogonal chemoselectivity is demonstrated in the streamlined synthesis of highly functionalized diaryl methane scaffolds using multi-halogenated substrates. Preliminary mechanistic experiments suggest both the sulfonium salt and the sulfur ylide are involved in the reaction, with the formation of sulfonium salt being the slowest step in the overall catalytic cycle.
- He, Zhiqi,Song, Feifei,Sun, Huan,Huang, Yong
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supporting information
p. 2693 - 2699
(2018/02/28)
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- A template-free approach to nanotube-decorated polymer surfaces using 3,4-phenylenedioxythiophene (PhEDOT) monomers
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In this work, novel 3,4-phenylenedioxythiophene (PhEDOT) monomers with alkyl, branched, and aromatic substituents were synthesized and tested for their efficacy at forming surfaces with unique wetting properties and surface morphology without the aid of surfactants. Monomers with a naphthalene substituent clearly showed the highest capacity to stabilize gas bubbles (O2 or H2) formed in solution during electrodeposition from trace water, resulting in the formation of nanotubes. Variation in the resulting density, diameter, and height of nanotubes was demonstrated by varying the electropolymerization protocol, conditions, or electrolyte used. The wetting induced by the nanotube formation results in the surfaces formed having both high contact angles with water (W) and strong adhesion, despite all polymers being intrinsically hydrophilic. This one-step and easily tunable approach to nanotube formation has potential to advance applications in membrane design, water transport and harvesting, as well as sensor design.
- Szczepanski, Caroline R.,M'Jid, Inès,Darmanin, Thierry,Godeau, Guilhem,Guittard, Frédéric
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p. 17308 - 17323
(2016/11/18)
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- Catalytic Tandem and One-Pot Dehydrogenation-Alkylation and -Insertion Reactions of Saturated Hydrocarbons with Alcohols and Alkenes
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The ruthenium-hydride catalyst has been successfully used for the tandem sp3 C-H dehydrogenation-alkylation reaction of saturated hydrocarbon substrates with alcohols to form the alkyl-substituted alkene and arene products. The analogous one-pot dehydrogenation-insertion of saturated ketones with alkenes and dienes directly yielded synthetically useful 2-alkylphenol and benzopyran products in a highly regio- and stereoselective manner without forming any wasteful byproducts. (Chemical Equation Presented).
- Kim, Junghwa,Pannilawithana, Nuwan,Yi, Chae S.
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p. 8395 - 8398
(2016/12/16)
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- Transition-metal-free cross-coupling reaction of benzylic halides with arylboronic acids leading to diarylmethanes
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The cross-coupling reaction between arylboronic acids and various benzylic halides proceeded without using a transition-metal catalyst to give the corresponding diarylmethanes in moderate to good yields.
- Ueda, Mitsuhiro,Nakakoji, Daiki,Kuwahara, Yuki,Nishimura, Kota,Ryu, Ilhyong
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p. 4142 - 4144
(2016/08/24)
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- Synthesis, structure, and catalytic applications for ortho - And meta -carboranyl based NBN pincer-Pd complexes
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o- and m-Carborane-based NBN pincer palladium complexes (oCB-L1)Pd, (oCB-L2)Pd, and (mCB-L1)Pd are synthesized in two steps from commercially available starting materials. The pincer complexes were prepared by the reaction of bis-[R(hydroxy)methyl]-1,2-dicarba-closo-dodecaborane (R = 2-pyridyl oCB-L1, 6-methyl-2-pyridyl oCB-L2) or bis-[2-pyridyl (hydroxy)methyl]-1,2-dicarba-meta- dodecaborane (mCB-L1) with [PdCl2(MeCN)2] under mild conditions. The X-ray structure determination of all carboranyl pincer complexes shows unambiguously B-H activation of the carborane cages. The results agree with the Pd-B bonds in all complexes exhibiting strong σ-electron donation. Theoretical calculations reveal the importance of considering the solid state intermolecular hydrogen bonding when investigating the trans influence in organometallic chemistry. A localized orbitals approach has also been applied to analyze the metal oxidation state in the carboranyl pincer complexes. Catalytic applications of (oCB-L1)Pd and (mCB-L1)Pd have shown the complexes are good catalyst precursors in Suzuki coupling in water and with very low amounts of catalyst loadings.
- Tsang, Min Ying,Vinas, Clara,Teixidor, Francesc,Planas, Jose Giner,Conde, Nerea,Sanmartin, Raul,Herrero, Maria Teresa,Dominguez, Esther,Lledos, Agusti,Vidossich, Pietro,Choquesillo-Lazarte, Duane
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p. 9284 - 9295
(2014/11/07)
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- Pd-catalyzed chemoselective threefold cross-coupling of triarylbismuths with benzylic bromides
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An efficient palladium-catalyzed protocol was demonstrated for the chemoselective cross-coupling of functionalized benzylic bromides with triarylbismuth reagents. Under the established conditions, catalyzed by palladium in the presence of K3PO
- Rao, Maddali L. N.,Dhanorkar, Ritesh J.
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p. 6794 - 6798
(2013/05/23)
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- Benzylation of aromatic compounds catalyzed by 3-methyl-1-sulfonic acid imidazolium tetrachloroaluminate and silica sulfuric acid under mild conditions
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In this work, efficient procedures for benzylation of a range of aromatic compounds by benzyl acetate in the presence of catalytic amounts of 3-methyl-1-sulfonic acid imidazolium tetrachloroaluminate ([Msim]AlCl 4) or silica sulfuric acid (SSA) under mild conditions are described. Simple methodology, easy workup procedure, clean reaction and reusability of the catalyst are some advantages of this work. Georg Thieme Verlag Stuttgart New York.
- Zolfigol, Mohammad Ali,Vahedi, Hooshang,Azimi, Saeid,Moosavi-Zare, Ahmad Reza
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p. 1113 - 1116
(2013/06/27)
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- Nickel-catalyzed cross couplings of benzylic ammonium salts and boronic acids: Stereospecific formation of diarylethanes via C-N bond activation
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We have developed a nickel-catalyzed cross coupling of benzylic ammonium triflates with aryl boronic acids to afford diarylmethanes and diarylethanes. This reaction proceeds under mild reaction conditions and with exceptional functional group tolerance. Further, it transforms branched benzylic ammonium salts to diarylethanes with excellent chirality transfer, offering a new strategy for the synthesis of highly enantioenriched diarylethanes from readily available chiral benzylic amines.
- Maity, Prantik,Shacklady-Mcatee, Danielle M.,Yap, Glenn P. A.,Sirianni, Eric R.,Watson, Mary P.
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supporting information
p. 280 - 285
(2013/02/25)
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- Direct alkylation of aromatics using alcohols in the presence of NaHSO 4/SiO2
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Simple and efficient procedure for alkylation of aromatics from alcohols in the presence of NaHSO4/SiO2 was developed. Various triaryl methanes were obtained in good yields in short reaction time. For instance the reaction of mesitylene with benzhydrol in the presence of NaHSO4/SiO2 gave the corresponding triaryl methane in a quantitative yield. NaHSO4/SiO2 was regenerated by simple treatment and could be recycled eight times without activity loss.
- Sato, Yuta,Aoyama, Tadashi,Takido, Toshio,Kodomari, Mitsuo
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supporting information; experimental part
p. 7077 - 7081
(2012/08/28)
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- Tin exchanged heteropoly tungstate: An efficient catalyst for benzylation of arenes with benzyl alcohol
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The partial exchange of tin with the protons of 12-tungstophosphoric acid (TPA) results in a highly active heterogeneous catalyst for benzylation of arenes with benzyl alcohol as benzylating agent. The catalysts were characterized by X-ray diffraction, Laser-Raman and FT-IR of pyridine adsorption. The catalytic activity depends significantly on the extent of tin exchanged with the protons of heteropoly tungstate. The characterization results suggest the presence of Lewis acidic sites by the exchange of tin. The catalyst with partial exchange of Sn showed high benzylation activity, which in turn related to variation in acidity of the catalysts. The catalyst is highly active for benzylation reaction irrespective of the nature of substituted arenes and benzyl alcohols. These catalysts are highly active compared to other acid catalysts used for benzylation of different arenes. The catalyst is easy to separate from reaction mixture and exhibit consistent activity upon reuse. The plausible reaction mechanism based on the role of both Lewis and Bronsted acid sites of the catalyst was discussed.
- Ramesh Kumar, Ch.,Rao, K.T. Venkateswara,Sai Prasad,Lingaiah
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experimental part
p. 17 - 24
(2011/04/21)
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- Br?nsted acid-catalyzed synthesis of diarylmethanes under non-genotoxic conditions
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Triflic acid and triflimide were found to efficiently catalyze the formation of a wide diversity of diarylmethanes from the non-genotoxic benzylic acetates and electron-rich arenes or heteroarenes. The reaction worked best with acetates capable of generating a stabilized benzylic cationic species. In most cases, the reactions were conveniently run in the absence of solvent under mild conditions.
- Mendoza, Oscar,Rossey, Guy,Ghosez, Léon
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experimental part
p. 2235 - 2239
(2011/05/05)
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- Coordination chemistry based approach to lipophilic inhibitors of 1-deoxy-D-xylulose-5-phosphate reductoisomerase
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1-Deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) in the non-mevalonate pathway found in most bacteria is a validated anti-infective drug target. Fosmidomycin, a potent DXR inhibitor, is active against Gram-negative bacteria. A coordination chemistry and structure based approach was used to discover a novel, lipophilic DXR inhibitor with an IC50 of 1.4 μM. It exhibited a broad spectrum of activity against Gram-negative and -positive bacteria with minimal inhibition concentrations of 20-100 μM (or 3.7-19 μg/mL).
- Deng, Lisheng,Sundriyal, Sandeep,Rubio, Valentina,Shi, Zheng-Zheng,Song, Yongcheng
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supporting information; experimental part
p. 6539 - 6542
(2010/04/04)
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- Palladium-catalyzed synthesis of diarylmethanes: Exploitation of carbanionic leaving groups
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A novel route to the synthesis of diarylmethanes via a Pd-catalyzed α-arylation of benzyl ketones is rseported. By harnessing the inherent reactivity of enolates, it is possible to circumvent the need for a transmetalating reagent such as boron for the co
- Schmink, Jason R.,Leadbeater, Nicholas E.
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supporting information; experimental part
p. 2575 - 2578
(2009/10/02)
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- Insights into the role of new palladium pincer complexes as robust and recyclable precatalysts for suzuki-miyaura couplings in neat water
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Suzuki-Miyaura biaryl and diarylmethane syntheses via the coupling of arylboronic acids with aryl and arylmethyl bromides are performed in water by means of two new CNC-type palladium pincer complexes. Good to excellent results (including high TON values and extended recycling procedures) are obtained in most cases for a range of electronically dissimilar halides and boronic acids. On the basis of a series of kinetics studies, transmission electron microscopy (TEM), mercury drop tests, and quantitative poisoning experiments, the real role of the latter palladacycles, closely linked to the formation and active participation of palladium nanoparticles, is discussed.
- Ines, Blanca,Sanmartin, Raul,Moure, Maria Jesus,Dominguez, Esther
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experimental part
p. 2124 - 2132
(2009/12/25)
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- A nonsymmetric pincer-catalyzed Suzuki-Miyaura arylation of benzyl halides and other nonactivated unusual coupling partners
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(Chemical Equation Presented) The catalytic activity of a PCN-type palladium pincer complex is evaluated in the construction of C(sp 2)-C(sp2) and C(sp2)-C(sp3) bonds by Suzuki-Miyaura cross-couplings employing nontypical substrates such as benzyl halides, α-haloenones, or alkylboronic acids as coupling partners. Most of the reported reactions are achieved in aqueous media, with all of the advantages implied.
- Ines, Blanca,Moreno, Isabel,SanMartin, Raul,Dominguez, Esther
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supporting information; experimental part
p. 8448 - 8451
(2009/04/11)
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- Conception, characterization and correlation of new marine odorants
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Via a synthetic sequence consisting of PPA-mediated Friedel-Crafts acylation of veratrol (8), Clemmensen reduction, demethylation with TMSI, Williamson ether synthesis employing 3-chloro-2-(chloromethyl)prop-1-ene and in-situ ruthenium tetroxide oxidation, numerous substituted benzo[b][1,4]dioxepinones 15-27 and 2,3-dihydro-1H-5,9-di-oxacyclohepta[f]indenones 7, 13 and 14 were prepared to study their odor-structure correlation. In the course of these studies, we discovered the extremely powerful new marine odorant 7-(3′ -methylbutyl)benzo[b][1,4]dioxepin-3-one (16). On the basis of the measured odor threshold data, an olfactophore model was constructed that rationalizes the observed odor intensities, and indicates an aliphatic hydrophobe at a distance of 6.3 A from the centre of the aromatic-ring binding site. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Kraft, Philip,Eichenberger, Walter
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p. 3735 - 3743
(2007/10/03)
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- Scandium(III) Triflate-Catalyzed Friedel-Crafts Alkylation Reactions
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The Sc(OTf)3-catalyzed Friedel-Crafts alkylation reaction with an alcohol, an arenecarbaldehyde or an arenecarbaldehyde acetal as the alkylating agent affords a diarylmethane or an allylbenzene derivative highly selectively. The salient feature of this reaction is that only a catalytic amount of Sc(OTf)3 can effect the reaction. Furthermore, Sc(OTf)3 is recoverable and reusable after the synthetic reaction. The Sc(OTf)3-catalyzed benzylation using an arenecarbaldehyde and 1,3-propanediol or their acetal affords diarylmethane as a sole product in excellent yields in sharp contrast to the original Friedel-Crafts reaction. Since no reaction occurs in the absence of 1,3-propanediol, the reaction is considered to proceed through a redox process including a hydride shift. The hydride shift mechanism is strongly supported by the experimental evidence. The reaction of benzaldehyde with benzene in the presence of 1,3-propanediol-1,1,3,3,-d4 gives rise to the deuterium incorporation into the benzylic carbon of diphenylmethane. Worthy of note is that 1,3-propanediol acts as the hydride source. Herein, diphenylmethyl 3-hydroxypropyl ether is assumed to be the most likely intermediate. In this reaction, Sc(OTf)3 catalyst effectively promotes initial acetal formation, electrophilic aromatic substitution, and successive intramolecular hydride transfer.
- Tsuchimoto, Teruhisa,Tobita, Kazuo,Hiyama, Tamejiro,Fukuzawa, Shin-Ichi
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p. 6997 - 7005
(2007/10/03)
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- Catalysis of Friedel-Crafts alkylation using virgin and Lewis acid doped bentonite k-10
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The reaction of benzyl chloride with active arenes to form diaryl methanes, has been found to be catalyzed by virgin India bentonite k-10.The doping of the bentonite k-10 with Lewis acids; AlCl3, FeCl3, and ZnCl2 has been found to enhance the catalytic actvity of the clay remarkably.Various parameters of the reaction have been optimised.Excellent results are obtained with respect to yield of the reaction, and time of the reaction.
- Natekar, R. S.,Samant S. D.
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p. 257 - 260
(2007/10/02)
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- Anomalous Acetoxylation of Aromatic Nuclei: Some Structural Requirements in the Substrate
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For certain aromatic nuclei, bromination in acetic acid in the presence of pyridine is accompanied by nuclear acetoxylation.As first observed with galbulin, when two alkoxyl groups, one meta and one para to a benzylic centre of the substrate are present, acetoxylation occurs at the intervening ortho position.Under the given conditions, acetoxylation occurs at position 8 of 6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydronaphthalene, and at position 2 of 3,4-dimethoxy diphenyl and triphenyl-methanes.Acetoxylation does not occur in the absence of either of the alkoxy groups or in the absence of pyridine, not does it occur in the pendant ring of 1-(3',4'-dimethoxyphenyl)-1,2,3,4-tetrahydronaphthalene.These results are consistent with the earlier suggestion that the reaction occurs by way of initial oxidative formation of a doubly benzylic cation
- Bandaranayake, Wickramasinghe M.,Riggs, Noel V.
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p. 115 - 129
(2007/10/02)
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