- Synthesis and structural reassignment of (+)-epicalyxin F
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We have established the structure of (+)-epicalyxin F through chemical synthesis. An acid-promoted rearrangement of synthetic benzopyran 6 led to the identification of the natural product as (3S,5S,7R)-epicalyxin F (22). Comparison with NMR spectra and op
- Tian, Xia,Rychnovsky, Scott D.
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- Bismuth-Catalyzed Oxidative Coupling of Arylboronic Acids with Triflate and Nonaflate Salts
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Herein we present a Bi-catalyzed cross-coupling of arylboronic acids with perfluoroalkyl sulfonate salts based on a Bi(III)/Bi(V) redox cycle. An electron-deficient sulfone ligand proved to be key for the successful implementation of this protocol, which allows the unusual construction of C(sp2)-O bonds using commercially available NaOTf and KONf as coupling partners. Preliminary mechanistic studies as well as theoretical investigations reveal the intermediacy of a highly electrophilic Bi(V) species, which rapidly eliminates phenyl triflate.
- Cornella, Josep,Peciukenas, Vytautas,Planas, Oriol
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supporting information
p. 11382 - 11387
(2020/07/14)
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- Catalytic Geminal Difluorination of Styrenes for the Construction of Fluorine-rich Bioisosteres
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A geminal difluorination of alkenes based on I(I)/I(III) catalysis is disclosed, which is compatible with a range of electronically and substitutionally diverse styrenes (27 examples, up to 89% yield). Employing inexpensive p-TolI as the organocatalyst, turnover is enabled by Selectfluor-mediated oxidation to generate the ArIF2 species in situ. Extension to include α-substituted styrenes bearing fluorine-containing groups is disclosed and provides an expansive platform for the generation of fluorine-rich architectures.
- Scheidt, Felix,Neufeld, Jessica,Sch?fer, Michael,Thiehoff, Christian,Gilmour, Ryan
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supporting information
p. 8073 - 8076
(2019/01/04)
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- Efficient cross-coupling of aryl/alkenyl triflates with acyclic secondary alkylboronic acids
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Aryl-secondary alkyl cross-coupling with aryl sulfonate esters as coupling partners remains a significant challenge. Efficient cross-coupling between aryl/alkenyl triflates and acyclic secondary alkylboronic acids is realized for the first time to provide a series of sterically congested acyclic secondary alkyl arenes/olefins in good to excellent yields. The employment of sterically bulky P,PO ligand L1/L2 is crucial for the high yields and selectivities. The method has enabled a concise and 4-step synthesis of a key intermediate of male contraceptive agent and PAF antagonist gossypol.
- Si, Tengda,Li, Bowen,Xiong, Wenrui,Xu, Bin,Tang, Wenjun
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supporting information
p. 9903 - 9909
(2017/12/12)
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- Pd-Catalyzed Conjunctive Cross-Coupling between Grignard-Derived Boron “Ate” Complexes and C(sp2) Halides or Triflates: NaOTf as a Grignard Activator and Halide Scavenger
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Catalytic enantioselective conjunctive cross-couplings that employ Grignard reagents are shown to furnish an array of nonracemic chiral organoboronic esters in an efficient and highly selective fashion. The utility of sodium triflate in facilitating this reaction is two-fold: it enables “ate” complex formation and overcomes catalytic inhibition by halide ions.
- Lovinger, Gabriel J.,Aparece, Mark D.,Morken, James P.
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supporting information
p. 3153 - 3160
(2017/03/11)
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- Base Catalysis Enables Access to α,α-Difluoroalkylthioethers
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A nucleophilic addition reaction of aryl thiols to readily available β,β-difluorostyrenes provides α,α-difluoroalkylthioethers. The reaction proceeds through an unstable anionic intermediate, prone to eliminate fluoride and generate α-fluorovinylthioethers. However, the use of base catalysis overcomes the facile β-fluoride elimination, generating α,α-difluoroalkylthioethers in excellent yields and selectivities.
- Orsi, Douglas L.,Easley, Brandon J.,Lick, Ashley M.,Altman, Ryan A.
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supporting information
p. 1570 - 1573
(2017/04/13)
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- Synthesis of Aldehydes by Organocatalytic Formylation Reactions of Boronic Acids with Glyoxylic Acid
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Reported herein is a conceptually novel organocatalytic strategy for the formylation of boronic acids. New reactivity is engineered into the α-amino-acid-forming Petasis reaction occurring between aryl boronic acids, amines, and glyoxylic acids to prepare aldehydes. The operational simplicity of the process and its ability to generate structurally diverse and valued aryl, heteroaryl, and α,β-unsaturated aldehydes containing a wide array of functional groups, demonstrates the practical utility of the new synthetic strategy.
- Huang, He,Yu, Chenguang,Li, Xiangmin,Zhang, Yongqiang,Zhang, Yueteng,Chen, Xiaobei,Mariano, Patrick S.,Xie, Hexin,Wang, Wei
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supporting information
p. 8201 - 8205
(2017/06/30)
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- Cellular protection of SNAP-25 against botulinum neurotoxin/A: Inhibition of thioredoxin reductase through a suicide substrate mechanism
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Botulium neurotoxins (BoNTs) are among the most lethal toxins known to man. They are comprised of seven serotypes with BoNT/A being the most deadly; yet, there is no approved therapeutic for their intoxication or one that has even advanced to clinical trials. Botulinum neurotoxicity is ultimately governed through light chain (LC) protease SNARE protein cleavage leading to a loss of neurotransmitter release. Pharmacological attempts to ablate BoNT/A intoxication have sought to either nullify cellular toxin entry or critical biochemical junctions found within its intricate mechanism of action. In these regards, reports have surfaced of nonpeptidic small molecule inhibitors, but few have demonstrated efficacy in neutralizing cellular toxicity, a key prerequisite before rodent lethality studies can be initiated. On the basis of a lead discovered in our BoNT/A cellular assay campaign, we investigated a family of N-hydroxysuccinimide inhibitors grounded upon structure activity relationship (SAR) fundamentals. Molecules stemming from this SAR exercise were theorized to be protease inhibitors. However, this proposition was overturned on the basis of extensive kinetic analysis. Unexpectedly, inhibitor data pointed to thioredoxin reductase (TrxR), an essential component required for BoNT protease translocation. Also unforeseen was the inhibitors' mechanism of action against TrxR, which was found to be brokered through a suicide-mechanism utilizing quinone methide as the inactivating element. This new series of TrxR inhibitors provides an alternative means to negate the etiological agent responsible for BoNT intoxication, the LC protease.
- Seki, Hajime,Xue, Song,Pellett, Sabine,?ilhár, Peter,Johnson, Eric A.,Janda, Kim D.
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supporting information
p. 5568 - 5575
(2016/06/01)
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- Copper-Catalyzed Enantioselective 1,6-Boration of para-Quinone Methides and Efficient Transformation of gem-Diarylmethine Boronates to Triarylmethanes
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Presented is the first enantioselective copper-catalyzed 1,6-conjugate addition of bis(pinacolato)diboron to para-quinone methides. The reaction proceeds with excellent yields and good to excellent enantioselectivities, and provides an attractive approach to the construction of optically active gem-diarylmehtine boronic esters. Additionally, the subsequent conversion of the derived potassium trifluoroborates into triarylmethanes with highly enantiospecificity was realized.
- Lou, Yazhou,Cao, Peng,Jia, Tao,Zhang, Yongling,Wang, Min,Liao, Jian
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supporting information
p. 12134 - 12138
(2015/10/12)
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- Me2s-induced highly selective reduction of aldehydes in the presence of ketones involving aldehyde-selective rate enhancement: A triruthenium cluster-catalyzed hydrosilylation
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Addition of appropriate amounts of Me2S unusually accelerated the hydrosilylation of aldehydes catalyzed by [Ru3(CO)7(Acy)] (1, Acy: μ3-η2,η3,η5-acenaphthylene). The reduction of
- Yumino, Shohei,Hashimoto, Toru,Tahara, Atsushi,Nagashima, Hideo
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supporting information
p. 1829 - 1831
(2015/02/19)
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- A practical in situ generation of the schwartz reagent. reduction of tertiary amides to aldehydes and hydrozirconation
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A new, highly efficient in situ protocol (Cp2ZrCl2/LiAlH(OBu-t)3) is described for the generation of the Schwartz reagent which provides a convenient method for the amide to aldehyde reduction and the regioselective hydrozirconation-iodination of alkynes and alkenes. Highlighted are chemoselective reductions of benzamides derived by directed ortho metalation (DoM) chemistry, allowing the synthesis of valuable 1,2,3-substituted benzaldehydes. The single-step, three-component process proceeds in a very short reaction time, shows excellent functional group compatibility, and uses inexpensive and long-storage stable reducing reagents.
- Zhao, Yigang,Snieckus, Victor
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supporting information
p. 390 - 393
(2014/04/03)
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- Highly active catalysts of bisphosphine oxides for asymmetric Heck reaction
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Bisphosphine oxides formed highly active asymmetric Heck catalysts, which were applied in asymmetric synthesis of pharmacologically active azacycles. Olefin insertion proceeded via cis pathways, different from P,N-ligands.
- Hu, Jian,Lu, Yunpeng,Li, Yongxin,Zhou, Jianrong
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supporting information
p. 9425 - 9427
(2013/10/01)
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- Achieving vinylic selectivity in Mizoroki-heck reaction of cyclic olefins
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In Heck reactions of cyclic olefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclic olefins of various ring size worked well. The desired isomers were produced by palladium-hydride-catalyzed isomerization of the initial products. Thus, a specific catalyst must be used so that it can perform two jobs under one set of reaction conditions. Copyright
- Wu, Xiaojin,Lu, Yunpeng,Hirao, Hajime,Zhou, Jianrong
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supporting information
p. 6014 - 6020
(2013/06/26)
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- Cesium carbonate mediated aryl triflate esters' deprotection
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A variety of diversely substituted aryl triflate esters were efficiently deprotected to the parent phenols by exposure to cesium carbonate in toluene. This procedure proved highly compatible with existing functional groups.
- Green, Alice E.,Agouridas, Vangelis,Deniau, Eric
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supporting information
p. 7078 - 7079
(2013/12/04)
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- Schwartz Reagents: Methods of In Situ Generation and Use
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Embodiments of the invention provide a method of using Schwartz Reagent, Cp2Zr(H)Cl, without accumulating or isolating it. Methods provide mixtures of Cp2ZrCl2, reductants that selectively reduce Cp2ZrCl2, and substrates. After reaction of Cp2ZrCl2 and the reductant, an intermediate reduction product is formed, apparently Schwartz Reagent. The in situ Schwartz Reagent then selectively reduces certain functional groups on the substrate. Substrates include tertiary amides, tertiary benzamides, aryl O-carbamates, and heteroaryl N-carbamates, which are reduced to aldehydes, benzaldehydes, aromatic alcohols, and heteroaromatics, respectively. Compared to prior methods, reagents are inexpensive and stable, reaction times are short, and reaction temperature in certain cases is conveniently room temperature. It has been estimated that using the in situ method described herein instead of synthesized or commercially obtained Schwartz Reagent provides a 50% reduction in cost.
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Page/Page column 7; 13
(2010/06/19)
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- Heterogeneous Pd/C-catalyzed ligand-free, room-temperature suzuki-miyaura coupling reactions in aqueous media
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A mild and efficient ligand-free Suzuki-Miyaura coupling reaction catalyzed by heterogeneous Pd/C was developed. Aryl bromides and triflates undergo the cross-coupling with aryl boronic acids in excellent yields without the presence of any additives in aqueous media at room temperature. Aryl vinyl boronic acids are also applicable to this coupling reaction and provide the trans-stilbene derivatives in high yields. The application of wet-type Pd/C to the coupling reaction was achieved without any loss of activity under aerobic conditions, and the reuse of Pd/C is feasible for a fifth run without significant loss of activity. Inductively coupled plasma (ICP) mass-spectrometric analysis of the filtrate from the reaction mixture of 4-bromonitrobenzene with phenylboronic acid demonstrated that the palladium metal hardly leached into the solution within the limits of the detector ( 1 ppm), thus suggesting that the present Suzuki-Miyaura reaction proceeded by heterogeneous catalysis.
- Maegawa, Tomohiro,Kitamura, Yoshiaki,Sako, Satoko,Udzu, Takahiro,Sakurai, Ai,Tanaka, Asami,Kobayashi, Yusuke,Endo, Koichi,Bora, Utpal,Kurita, Takanori,Kozaki, Atsushi,Monguchi, Yasunari,Sajiki, Hironao
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p. 5937 - 5943
(2008/02/13)
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- A polystyrene-supported triflating reagent for the synthesis of aryl triflates
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An insoluble polystyrene-supported triflating reagent has been prepared by suspension co-polymerization of N-(4-vinylphenyl)trifluoromethanesulphonimide, styrene and the JandaJel cross-linker. This reagent, in the presence of triethylamine, allows for the efficient synthesis of aryl triflates from a wide range of phenols in a process that permits the desired product to be isolated from the reaction mixture in essentially pure form via several filtration and concentration operations. Adding to the utility of this reagent is its ability to be easily recovered, regenerated and reused. Both soluble and insoluble bifunctional polymers containing trialkylamine moieties in addition to triflimide groups were also prepared and examined as triflating reagents. Unfortunately these reagents afforded only modest yields of the desired products in representative reactions. Graphical Abstract.
- Chung, Cecilia Wan Ying,Toy, Patrick H.
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p. 709 - 715
(2007/10/03)
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- Preparation and Palladium-Catalyzed Cross-Coupling of Aryl Triethylammonium Bis(catechol) Silicates with Aryl Triflates
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Pentavalent aryl and heteroaryl bis(catechol) silicates undergo palladium-catalyzed cross-coupling with aryl and heteroaryl triflates in the presence of a fluoride source in excellent yields. These solid, air-stable bis(catechol) silicates are prepared from a high-yielding displacement reaction between catechol and an aryl siloxane in the presence of an amine base. The cross-coupling reaction is tolerant of a wide range of electron-donating and electron-withdrawing groups. Several examples of di-ortho-substituted triflates are successfully coupled with these reagents.
- Seganish, W. Michael,DeShong, Philip
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p. 1137 - 1143
(2007/10/03)
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- Palladium-catalyzed phosphination of functionalized aryl triflates
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Catalytic user-friendly approach to the syntheses of various functionalized aromatic phosphines from their corresponding substituted aryl triflates and triarylphosphines was accomplished. This method is carried out in neutral media and compatible with man
- Kwong, Fuk Yee,Lai, Chi Wai,Yu, Michael,Tian, Yuan,Chan, Kin Shing
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p. 10295 - 10305
(2007/10/03)
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- Benzenoid derivatives of 15-hydroxyeicosatetraenoic acid and methods of their use in treating dry eye disorders
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Benzenoid HETE derivatives and methods of their use for treating dry eye are disclosed.
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- (+)-4-Phosphonophenylglycine (PPG) a new group III selective metabotropic glutamate receptor agonist
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A new synthesis of (R,S)-PPG (4-phosphonophenylglycine) and the separation of the protected enantiomers leading after deprotection to (+)- and (-)-PPG are described. Pharmacological characterization at the group III metabotropic glutamate receptors hmGluR4a and hmGluR7b revealed (+)-PPG as the active enantiomer. (C) 2000 Elsevier Science Ltd. All rights reserved.
- Gasparini, Fabrizio,Inderbitzin, Werner,Francotte, Eric,Lecis, Gabrielle,Richert, Paul,Dragic, Zorica,Kuhn, Rainer,Flor, Peter J.
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p. 1241 - 1244
(2007/10/03)
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- 1-[4-(3-Phenylalkyl)phenyl]-2-aminopropanes as 5-HT(2A) partial agonists
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Phenylalkylamines such as 1-(4-bromo-2,5-dimethoxyphenyl)-2-aminopropane (DOB; 1a) and its corresponding iodo derivative DOI (2) are commonly used 5-HT2 serotonin agonists. Previous studies have established that the 2,5-dimethoxy substitution p
- Dowd,Herrick-Davis,Egan,DuPre,Smith,Teitler,Glennon
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p. 3074 - 3084
(2007/10/03)
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- Synthesis of N-Fmoc-4-[(diethylphosphono)-2',2'-difluoro-1'- hydroxyethyl]phenylalanine, a novel phosphotyrosyl mimic for the preparation of signal transduction inhibitory peptides
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The synthesis of a novel non-hydrolyzable phosphotyrosyl mimic N-Fmoc-4- [(diethylphosphono)-2',2'-difluoro-1'-hydroxyethyl]-DL-phenylalanine is reported. (C) 2000 Elsevier Science Ltd.
- Chetyrkina, Svitlana,Estieu-Gionnet, Karine,La?n, Georges,Bayle, Mireille,Déléris, Gérard
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p. 1923 - 1926
(2007/10/03)
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- (R,S)-4-phosphonophenylglycine, a potent and selective group III metabotropic glutamate receptor agonist, is anticonvulsive and neuroprotective in vivo
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Group III metabotropic glutamate receptors (mGluRs) are thought to modulate neurotoxicity of excitatory amino acids, via mechanisms of presynaptic inhibition, such as regulation of neurotransmitter release. Here, we describe (R,S)-4-phosphonophenylglycine
- Gasparini,Bruno,Battaglia,Lukic,Leonhardt,Inderbitzin,Laurie,Sommer,Varney,Hess,Johnson,Kuhn,Urwyler,Sauer,Portet,Schmutz,Nicoletti,Flor, Peter J.
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p. 1678 - 1687
(2007/10/03)
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- Convenient synthesis of aromatic thiols from phenols
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Aromatic thiols were synthesised from phenols in good yield and under mild conditions by reaction of the corresponding triflates with sodium triisopropylsilanethiolate (NaSTIPS) and subsequent deprotection.
- Arnould, Jean Claude,Didelot, Myriam,Cadilhac, Caroline,Pasquet, Marie Jeanne
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p. 4523 - 4524
(2007/10/03)
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- Cross-coupling reaction of pentacoordinate alkenylsilicates with organic halides and triflates catalyzed by a palladium complex
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Isolated pentacoordinate alkoxy-substituted alkenylsilicates, are readily prepared by mixing alkenyltrialkoxysilane, catechol and triethylamine at room temperature.Cross-coupling reactions of these alkenylsilicates with organic halides or triflates are catalyzed by a palladium complex and proceed very smoothly and cleanly to give the corresponding alkenes.The cross-coupling reactions could be also attained by a one pot operation without isolation of pentacoordinate organosilicates.The mechanism of this cross-coupling reaction is also described here. alkoxy-substituted alkenylsilicate / pentacoordinate silicate / cross-coupling / palladium catalyst / aryl halide / aryl triflate / styrene derivative / 1,3-diene
- Hojo, Makoto,Murakami, Chikara,Aihara, Hidenori,Komori, Ei-ichi,Kohra, Shinya,et al.
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p. 499 - 508
(2007/10/02)
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- Reaction of Triflates with Potassium Diethyl Phosphite. Formation of Phosphate Esters
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Phenyl triflate and substituted analogues react with potassium diethyl phosphite in liquid ammonia to form aryl diethyl phosphate esters.The reaction formally involves loss of trifluoromethanesulfinate ion from the triflate and concomitant oxidation of phosphorus to the phosphate stage.Preliminary data suggest that, in a series of triflates, reactivity follows the order aryl > cyclohexenyl > cyclopropyl > alkyl.Studies on aryl triflates with added labeled phenoxide rule out a mechanism involving free phenoxide ion, i.e., displacement of phenoxide by nucleophilic attack of diethyl phosphite ion on sulfur followed by phosphorylation of displaced phenoxide.Three potential mechanisms, including one involving initial attack of phosphorus at sulfur, a biphilic insertion mechanism, and one involving nucleophilic attack on oxygen, are suggested, all of which could account for these observations.
- Creary, Xavier,Benage, Brigitte,Hilton, Kathryn
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p. 2887 - 2891
(2007/10/02)
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