- Strain-release electrophilic activation via E-cycloalkenones
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UVA irradiation (ca. 350 nm) of a mixture of cyclic enones and nitrogen heterocycles leads to efficient formation of the 1,4-adducts in a variety of solvents, at room temperature. These reactions likely proceed through strained E-cycloalkenone intermediates, as suggested by lowtemperature generation/trapping experiments monitored by 1H NMR. These results demonstrate that E-cycloalkenones are good electrophiles despite their known tendency to favor a conformation in which the carbonyl is not fully conjugated with the double bond.
- Moran, Joseph,Dornan, Peter,Beauchemin, Andre M.
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Read Online
- Nucleophilic Attack on Nitrogen in Tetrazines by Silyl-Enol Ethers
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The nucleophilic addition of silyl-enol ethers to nitrogen in 3-monosubstituted s-tetrazines mediated by BF3 is reported. The preference for this azaphilic addition over the usually observed inverse electron demand Diels-Alder reactions was evaluated theoretically and corroborated by experiments. The substrate dependency of this unusual reaction was rationalized by determination of the activation barriers and on the basis of the activation strain model by employing density functional theory.
- Schnell, Simon D.,Schilling, Mauro,Sklyaruk, Jan,Linden, Anthony,Luber, Sandra,Gademann, Karl
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supporting information
p. 2426 - 2430
(2021/04/05)
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- Boron Trifluoride-Mediated Cycloaddition of 3-Bromotetrazine and Silyl Enol Ethers: Synthesis of 3-Bromo-pyridazines
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Pyridazines are important scaffolds for medicinal chemistry or crop protection agents, yet the selective preparation of 3-bromo-pyridazines with high regiocontrol remains difficult. We achieved the Lewis acid-mediated inverse electron demand Diels-Alder reaction between 3-monosubstituted s-tetrazine and silyl enol ethers and obtained functionalized pyridazines. In the case of 1-monosubstituted silyl enol ethers, exclusive regioselectivity was observed. Downstream functionalization of the resulting 3-bromo-pyridazines was demonstrated utilizing several cross-coupling protocols to synthesize 3,4-disubstituted pyridazines with excellent control over the substitution pattern.
- Schnell, Simon D.,González, Jorge A.,Sklyaruk, Jan,Linden, Anthony,Gademann, Karl
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p. 12008 - 12023
(2021/08/24)
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- Last of the gem-Difluorocycloalkanes 2: Synthesis of Fluorinated Cycloheptane Building Blocks
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The gem-difluorocycloalkane family was extended to all possible regioisomers of the gem-difluorocycloheptane, monofunctionalized by carboxilic-, amino- or keto- group, that were synthesized on a multigram scale. The preparation of the corresponding building blocks was achieved from readily accessible starting materials either via six-membered ring homologation or deoxofluorination of the appropriate seven-membered cyclic ketones.
- Herasymchuk, Maksym,Melnykov, Kostiantyn P.,Yarmoliuk, Dmytro V.,Serhiichuk, Dmytro,Rotar, Valeriia,Pukhovoi, Timur,Kuchkovska, Yuliya O.,Holovach, Sergey,Volochnyuk, Dmitriy M.,Ryabukhin, Sergey V.,Grygorenko, Oleksandr O.
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p. 6561 - 6569
(2021/02/16)
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- Three-Component Coupling of Acyl Fluorides, Silyl Enol Ethers, and Alkynes by P(III)/P(V) Catalysis
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We report herein on the phosphine-catalyzed hydrovinylation reaction by three-component coupling of acyl fluorides, silyl enol ethers, and alkynoates. The key to the success of the reaction is the formal transmetalation between pentacoordinate P(V) species (i.e., fluorophosphorane) and a silyl enol ether, which allows for C-C bond formation between the polarity-mismatched sites. The bond formation that cannot be attained even by transition metal catalysis is accomplished by a P(III)/P(V) manifold.
- Fujimoto, Hayato,Kusano, Momoka,Kodama, Takuya,Tobisu, Mamoru
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supporting information
p. 18394 - 18399
(2021/11/22)
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- Direct C-H α-Arylation of Enones with ArI(O2CR)2 Reagents
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α-Arylation of α,β-unsaturated ketones constitutes a powerful synthetic transformation. It is most commonly achieved via cross-coupling of α-haloenones, but this stepwise strategy requires prefunctionalized substrates and expensive catalysts. Direct enone C-H α-arylation would offer an atom- and step-economical alternative, but such reports are scarce. Herein we report the metal-free direct C-H arylation of enones mediated by hypervalent iodine reagents. The reaction proceeds via a reductive iodonium Claisen rearrangement of in situ-generated β-pyridinium silyl enol ethers. The aryl groups are derived from ArI(O2CCF3)2 reagents, which are readily accessed from the parent iodoarenes. The reaction is tolerant of a wide range of substitution patterns, and the incorporated arenes maintain the valuable iodine functional handle. Mechanistic investigations implicate arylation via an umpoled "enolonium" species and show that the presence of a β-pyridinium moiety is critical for the desired C-C bond formation.
- Sousa E Silva, Felipe Cesar,Van, Nguyen T.,Wengryniuk, Sarah E.
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supporting information
p. 64 - 69
(2020/01/22)
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- Manganese-Catalyzed Electrochemical Deconstructive Chlorination of Cycloalkanols via Alkoxy Radicals
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A manganese-catalyzed electrochemical deconstructive chlorination of cycloalkanols has been developed. This electrochemical method provides access to alkoxy radicals from alcohols and exhibits a broad substrate scope, with various cyclopropanols and cyclobutanols converted into synthetically useful β- and γ-chlorinated ketones (40 examples). Furthermore, the combination of recirculating flow electrochemistry and continuous inline purification was employed to access products on a gram scale.
- Allen, Benjamin D. W.,Hareram, Mishra Deepak,Seastram, Alex C.,McBride, Tom,Wirth, Thomas,Browne, Duncan L.,Morrill, Louis C.
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supporting information
p. 9241 - 9246
(2019/11/19)
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- Metal complex, organic electroluminescent device, organic electroluminescent material
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The invention relates to a metal complex, an organic electroluminescent device containing the metal complex and an organic electroluminescent material. The metal complex has a molecular formula of M(LA)(m-n)(LC)n, wherein M is metal element Ir, m is the oxidation valence state of metal M, n is an integer of 1 or more and is less than m. The electroluminescent device containing the metal complex emits red light, and has a high external quantum efficiency; and the material has good thermal stability, the service life of the device can be prolonged, the material is easily prepared and purified and can be used as an ideal choice for a luminescent material of the organic electroluminescent device.
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Paragraph 0228; 0231-0233
(2019/04/27)
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- C?O coupling of Malonyl Peroxides with Enol Ethers via [5+2] Cycloaddition: Non-Rubottom Oxidation
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Malonyl peroxides act both as oxidants and reagents for C?O coupling in reactions with methyl and silyl enol ethers. In the proposed conditions, the oxidative C?O coupling of malonyl peroxides with enol ethers selectively proceeds, bypassing the traditional Rubottom hydroxylation of enol ethers by peroxides. It was observed that the oxidative [5+2] cycloaddition of malonyl peroxides and enol ethers is the key stage of the discovered process. Oxidative C?O coupling of silyl enol ethers leads to the formation of α-acyloxyketones with a free carboxylic acid group. A specially developed preparative one-pot procedure transforms ketones via silyl enol ethers formation and the following coupling into α-acyloxyketones with yields 35–88%. The acid-catalyzed coupling with methyl enol ethers gives remarkable products while retaining the easily oxidizable enol fragment. Furthermore, these molecules contain a free carboxylic acid group, thus these nontrivial products contain two usually incompatible acid and enol ether groups. (Figure presented.).
- Vil', Vera A.,Gorlov, Evgenii S.,Bityukov, Oleg V.,Barsegyan, Yana A.,Romanova, Yulia E.,Merkulova, Valentina M.,Terent'ev, Alexander O.
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supporting information
p. 3173 - 3181
(2019/05/15)
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- Ni-Catalyzed β-Alkylation of Cyclopropanol-Derived Homoenolates
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Metal homoenolates are valuable synthetic intermediates which provide access to β-functionalized ketones. In this report, we disclose a Ni-catalyzed β-alkylation reaction of cyclopropanol-derived homoenolates using redox-active N-hydroxyphthalimide (NHPI) esters as the alkylating reagents. The reaction is compatible with 1°, 2°, and 3° NHPI esters. Mechanistic studies imply radical activation of the NHPI ester and 2e β-carbon elimination occurring on the cyclopropanol.
- Mills, L. Reginald,Zhou, Cuihan,Fung, Emily,Rousseaux, Sophie A. L.
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supporting information
p. 8805 - 8809
(2019/11/03)
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- (Poly)cationic λ3-Iodane-Mediated Oxidative Ring Expansion of Secondary Alcohols
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Herein, a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3-iodanes (N-HVIs) is reported. Excellent levels of selectivity are achieved for C–O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting hexafluoroisopropanol (HFIP) acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations. The utility of this methodology for late-stage natural product derivatization was also demonstrated, providing a new tool for diversity-oriented synthesis and complexity-to-diversity (CTD) efforts. Preliminary mechanistic investigations reveal a strong effect of alcohol conformation on the reactive pathway, thus providing a predictive power in the application of this approach to complex molecule synthesis.
- Walters, Jennifer C.,Tierno, Anthony F.,Dubin, Aimee H.,Wengryniuk, Sarah E.
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supporting information
p. 1460 - 1464
(2018/04/06)
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- FLP-Catalyzed Transfer Hydrogenation of Silyl Enol Ethers
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Herein we report the first catalytic transfer hydrogenation of silyl enol ethers. This metal free approach employs tris(pentafluorophenyl)borane and 2,2,6,6-tetramethylpiperidine (TMP) as a commercially available FLP catalyst system and naturally occurring γ-terpinene as a dihydrogen surrogate. A variety of silyl enol ethers undergo efficient hydrogenation, with the reduced products isolated in excellent yields (29 examples, 82 % average yield).
- Khan, Imtiaz,Reed-Berendt, Benjamin G.,Melen, Rebecca L.,Morrill, Louis C.
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supporting information
p. 12356 - 12359
(2018/09/18)
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- One-Pot Synthesis of Silylated Enol Triflates from Silyl Enol Ethers for Cyclohexynes and 1,2-Cyclohexadienes
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Regiocontrolled synthesis of precursors for strained cyclohexynes and 1,2-cyclohexadienes is described based on one-pot rearrangement of silyl enol ether followed by formation of enol triflate. Treatment of silyl enol ether with a combination of LDA and tBuOK led to the migration of the silyl group to generate α-silyl enolate, which was treated with Comins' reagent to provide the corresponding enol triflate. The transient α-silylated lithium enolate was smoothly isomerized in the presence of stoichiometric amount of water within one hour at room temperature, providing precursors for cyclohexynes exclusively in one pot. Effects of silyl groups, isomerization of the lithium enolate, and regiocontrolled generation of these precursors for these strained molecules were also investigated.
- Inoue, Kazuki,Nakura, Ryo,Okano, Kentaro,Mori, Atsunori
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supporting information
p. 3343 - 3347
(2018/07/13)
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- A Solvent-Free Reaction for Silyl Enol Ethers Synthesis
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Silyl enol ethers are extremely useful nucleophilic intermediates for chemical transformations because they are synthetically versatile substrates for a wide range of C-C bond-forming reactions. Here, we present a new, mild, and solvent-free procedure for the synthesis of silyl enol ethers that employs a catalytic amount of solid-supported base and an equimolar amount of N, O -(bistrimethylsilyl)acetamide as a silylating agent.
- Morozzi, Chiara,Rosati, Ornelio,Curini, Massimo,Lanari, Daniela
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supporting information
p. 126 - 130
(2017/12/28)
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- Tuning the Reactivity of Functionalized Diallylic Alcohols: Br?nsted versus Lewis Acid Catalysis
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The chemodivergent reactivity of bifunctional, enol thioether-containing diallylic alcohols in acidic medium is disclosed, highlighting the difference between strong Lewis acid and mild Br?nsted acid catalysis. In the presence of bismuth(III) triflate, allylic alcohol activation affords diversely substituted cyclopentenones in a Nazarov-type electrocyclization, whereas activation of the thioenol ether by p-toluenesulfonic acid provides an entry to α-sulfenylated β,γ-unsaturated ketones. Both methods represent a facile access to the corresponding products under mild conditions, using inexpensive and non-toxic catalytic systems.
- Lempenauer, Luisa,Du?ach, Elisabet,Lemière, Gilles
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supporting information
p. 10285 - 10288
(2017/08/07)
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- Unprecedented alkylation of silicon enolates with alcohols via carbenium ion formations catalyzed by tin hydroxide-embedded montmorillonite
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The solid acid, tin hydroxide-embedded montmorillonite, catalyzes the unprecedented alkylation of various silicon enolates with primary, secondary and tertiary benzylic alcohols as well as secondary allylic alcohols. The acid catalysis of Sn-Mont was not only higher than that of the other ion-exchanged montmorillonites (M-Mont; M?=?H, Ti, Fe and Al), but also higher than that of the typical homogeneous acid catalysts such as BF3·OEt2, TMSOTf and TfOH.
- Tandiary, Michael Andreas,Asano, Masashi,Hattori, Taiki,Takehira, Satoshi,Masui, Yoichi,Onaka, Makoto
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supporting information
p. 1925 - 1928
(2017/04/27)
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- Sc(OTf)3-Catalyzed Addition of Bromomagnesium 2-Vinyloxy Ethoxide to Various Aldehydes Leading to Protected Aldol Products
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The addition of bromomagnesium 2-vinyloxy ethoxide to various aldehydes in the presence of 10 mol% Sc(OTf)3 provides a broad range of functionalized protected aldol compounds. The enantioselective preparation of these aldols can be achieved via a Swern oxidation-CBS reduction sequence. Use of the dioxolane derived from 2-bromocyclohexanone provides the expected aldol product as the anti diastereoisomer (dr >99:1).
- Quinio, Pauline,Kohout, Laura,Roman, Daniela Sustac,Gaar, Jakob,Karaghiosoff, Konstantin,Knochel, Paul
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supporting information
p. 1715 - 1719
(2016/07/06)
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- 3D-Printing inside the Glovebox: A Versatile Tool for Inert-Gas Chemistry Combined with Spectroscopy
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3D-Printing with the well-established 'Fused Deposition Modeling' technology was used to print totally gas-tight reaction vessels, combined with printed cuvettes, inside the inert-gas atmosphere of a glovebox. During pauses of the print, the reaction flasks out of acrylonitrile butadiene styrene were filled with various reactants. After the basic test reactions to proof the oxygen tightness and investigations of the influence of printing within an inert-gas atmosphere, scope and limitations of the method are presented by syntheses of new compounds with highly reactive reagents, such as trimethylaluminium, and reaction monitoring via UV/VIS, IR, and NMR spectroscopy. The applicable temperature range, the choice of solvents, the reaction times, and the analytical methods have been investigated in detail. A set of reaction flasks is presented, which allow routine inert-gas syntheses and combined spectroscopy without modifications of the glovebox, the 3D-printer, or the spectrometers. Overall, this demonstrates the potential of 3D-printed reaction cuvettes to become a complementary standard method in inert-gas chemistry.
- Lederle, Felix,Kaldun, Christian,Namyslo, Jan C.,Hübner, Eike G.
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p. 255 - 266
(2016/05/19)
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- Rhodium-catalyzed borylation of aryl and alkenyl pivalates through the cleavage of carbonoxygen bonds
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Rhodium-catalyzed borylation reactions of aryl and alkenyl pivalates, using a diboron reagent, via the cleavage of carbonoxygen bonds have been developed. The inert nature of the pivalate moiety enables relatively complex aryl boronates to be synthesized via the tandem cross-coupling of carbonhalogen and carbonoxygen bonds.
- Kinuta, Hirotaka,Hasegawa, Junya,Tobisu, Mamoru,Chatani, Naoto
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supporting information
p. 366 - 368
(2015/03/30)
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- Halogenative difluorohomologation of ketones
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A method for the difluorohomologation of ketones accompanied by halogenation of a C-H bond is described. The reaction involves silylation, difluorocarbene addition using Me3SiCF2Br activated by a bromide ion, and halogenation of intermediate cyclopropanes with N-bromo- or N-iodosuccinimide. The whole process is performed without isolation of intermediates. The resulting α,α-difluoro-β-halo-substituted ketones can be readily converted into fluorine containing pyrazole derivatives and oxetanes.
- Fedorov, Oleg V.,Kosobokov, Mikhail D.,Levin, Vitalij V.,Struchkova, Marina I.,Dilman, Alexander D.
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p. 5870 - 5876
(2015/06/16)
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- Highly stereoselective oxazaborolidinium ion catalyzed synthesis of (Z)-silyl enol ethers from alkyl aryl ketones and trimethylsilyldiazomethane
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Highly stereoselective (Z)-silyl enol ethers were prepared from alkyl aryl ketones and trimethylsilyldiazomethane (TMSD) using an oxazaborolidinium ion catalyst. In addition, ring-expanded silyl enol ethers were successfully constructed from cyclic ketones. Their synthetic utilities were shown by sequential Mukaiyama aldol and [2 + 2]-cycloaddition reactions.
- Kang, Byung Chul,Shim, Su Yong,Ryu, Do Hyun
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supporting information
p. 2077 - 2079
(2014/05/06)
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- A catalytic, mild and efficient protocol for the C-3 aerial hydroxylation of oxindoles
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A mild, high yielding approach to C-3 hydroxylated oxindoles using catalytic quantities of tetrabutylammonium fluoride and air as the stoicheiometric oxidant is reported over a wide range of substitution patterns.
- Buckley, Benjamin R.,Fernández D.-R., Beatriz
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supporting information
p. 843 - 846
(2013/03/13)
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- METHOD FOR PRODUCING SILYLENOL ETHERS
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The present invention provides a method for producing a silyl enol ether compound, which is convenient, has highly broad utility and places a low environmental load (less waste). The present invention relates to a method for producing silyl enol ether compound (3), including reacting ketone or aldehyde compound (1) with allylsilane compound (2) in the presence of a base and 0.00001 to 0.5 equivalents of an acid catalyst relative to ketone or aldehyde compound (1), wherein R1 is a hydrogen atom, an alkyl group, an aryl group or the like; R2 and R3 are each a hydrogen atom, a halogen atom, an alkyl group, an aryl group or the like; R1 and R3, R1 and R2, or R2 and R3 optionally form a ring, together with the carbon atom(s) bonded thereto; R4 , R5 and R6 are each a hydrogen atom, an alkyl group or the like; two of R4, R5 and R6 optionally form a ring; R7, R8, R9, R10 and R11 are each a hydrogen atom, an alkyl group or the like; two of R7, R8, R9, R10 and R11 optionally form a ring.
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Paragraph 0097-0098
(2013/03/26)
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- The introduction of a double bond on the steroid skeleton - The preparation of enol silyl ether derivatives from vicinal diols
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The ways of converting steroid vicinal diol into an unsaturated derivative were studied with the intention of preparing suitable precursors for the introduction of deuterium or tritium into the molecules of brassinosteroids. The model vicinal diol compound, 2α,3α-dihydroxy-5α-pregnane-6, 20-dione (3), was converted with high regioselectivity to the α-hydroxy ketone derivative, 2α-hydroxy-5α-pregnane-3,6,20-trione (8), in a 75% yield. The attempts to convert α-hydroxy ketone 8 to the dioxolene derivative, 2α,3α-(isopropylidenedioxy)-5α-pregn-2-ene-6,20- dione (6), failed. The conditions for the conversion of ketone to the corresponding enol trialkylsilyl ether were optimized using cyclohexanone as a model compound. The best and reproducible results were obtained by using tert-butyldimethylsilyl trifluoromethansulfonate (TBDMSiOTf) as the silylating reagent and triethylamine as the base. Under these conditions, the 3,6,20-trione (8) was converted to 2,3-bis(tert-butyldimethylsilyloxy)-5α-pregn-2-ene- 6,20-dione (14) with a 66% yield.
- Marek, Ales,Klepetarova, Blanka,Elbert, Tomas
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experimental part
p. 443 - 456
(2011/12/21)
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- A convenient transformation of 2-alkylidenecycloalkanones into alkyl-substituted bicyclo[ n.1.0]alkan-1-ols: Application to the synthesis of capsaicin
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Treatment of 2-alkylidenecycloalkanones with hydrogen iodide in benzene and subsequent reaction of the obtained -iodo ketones with zinc dust in THF in the presence of chlorotrimethylsilane or titanium(IV) chlorotriisopropoxide led to exo- and endo-(n+3)-alkylbicyclo[n.1.0]alkan-1-ols in high yields. Cyclization of the intermediate -iodo ketones under these conditions proceeded in a moderate to good diastereoselectivity, and the resulted bicyclic cyclopropanols were easily separated by column chromatography over silica gel. exo-7- Isopropylbicyclo[4.1.0]heptan-1-ol obtained in this manner was efficiently employed as a key intermediate in the synthesis of capsaicin. Georg Thieme Verlag Stuttgart - New York.
- Kananovich, Dzmitry G.,Zubrytski, Dzmitry M.,Kulinkovich, Oleg G.
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experimental part
p. 1043 - 1046
(2010/06/14)
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- Mechanistic studies on α-trifluoromethylation of ketones via silyl enol ethers and its application to other carbonyl compounds
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(Chemical Equation Presented) Synthesis of α-CF3 carbonyl compounds has been recognized to be difficult up to now because the polarization of CF3δ--Iδ+ is opposite to that of CH3δ+-Iδ-, and this makes it difficult to introduce CF3+ unit to enolates. We recently reported an effective R-trifluoromethylation of ketones by using Et 2Zn with Rh catalyst, but the mechanism has not fully been cleared. Now, we carried out the detailed mechanistic studies and found the involvement of a highly reactive alkylrhodium complex which derived from Et2Zn and RhCl(PPh3)3 in this α-trifluoromethylation. Furthermore, this α-trifluoromethylation was applied to other types of carbonyl compounds in good yields.
- Sato, Kazuyuki,Yuki, Takashi,Yamaguchi, Ryoji,Hamano, Tetsuya,Tarui, Atsushi,Omote, Masaaki,Kumadaki, Itsumaro,Ando, Akira
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supporting information; experimental part
p. 3815 - 3819
(2009/10/01)
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- The effects of C-S and C-Se bonds on torquoselectivity: stereoselective olefination of α-thio and α-selenoketones with ynolates
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Highly Z-selective olefination of acyclic α-thio and α-selenoketones with ynolates has been achieved, and the theoretical calculations of the transition states in the ring-opening of the intermediates, the β-lactone enolates, revealed that the torquoselectivity was controlled by the secondary orbital interactions between the σ orbital of the C-S bond or a lone pair orbital on the S and σ* orbitals of the breaking C-O bond, and the σ orbital of the breaking C-O bond or a lone pair orbital on the O on the ring and the σ* orbitals of the C-S bond. The synthetic applications of the resulting olefins are also shown.
- Yoshikawa, Takashi,Mori, Seiji,Shindo, Mitsuru
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experimental part
p. 8832 - 8838
(2010/04/06)
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- ScIII-Doped zeolites as new heterogeneous catalysts: mukaiyama aldol reaction
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ScIII-doped solids based on zeolite materials have been investigated for the first time as catalysts in organic synthesis. Sc III-USY zeolite proved to be a novel and very efficient heterogeneous catalyst for the Mukaiyama aldol reaction. This easy-to-prepare catalyst exhibited wide scope and compatibility with functional groups and is very simple to use, easy to remove (by simple filtration), and is recyclable (up to three times without loss of activity).
- Olmos, Andrea,Alix, Aurelien,Sommer, Jean,Pale, Patrick
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supporting information; experimental part
p. 11229 - 11234
(2010/04/28)
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- Di-tert-butylmagnesium as an atom-efficient, carbon-centred base reagent for the preparation of silyl enol ethers from ketones
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Di-tert-butylmagnesium has been found to be a reactive, yet non-nucleophilic and non-reductive, carbon-centred base for the deprotonation of a series of ketones. This reagent demonstrates equally high reactivity when used as either the pre-formed reagent, or in a more accessible one-pot protocol from the parent Grignard reagent, and offers improved atom-efficiency over more traditionally employed bases. Georg Thieme Verlag Stuttgart.
- Kerr, William J.,Watson, Allan J. B.,Hayes, Douglas
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scheme or table
p. 1386 - 1390
(2009/04/06)
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- In situ generation of Mes2Mg as a non-nucleophilic carbon-centred base reagent for the efficient one-pot conversion of ketones to silyl enol ethers
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Treatment of commercially available MesMgBr with 1,4-dioxane produces the key Mes2Mg reagent in situ which then mediates the deprotonation of ketones to deliver trimethylsilyl enol ethers, at readily accessible temperatures and without any nucleophilic addition, in an expedient and high yielding one-pot process. The Royal Society of Chemistry.
- Kerr, William J.,Watson, Allan J. B.,Hayes, Douglas
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experimental part
p. 1238 - 1243
(2008/10/09)
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- Sc(OTf)3-catalyzed smooth tandem [3+2] cycloaddition/ring opening of donor-acceptor cyclopropane 1,1-diesters with enol silyl ethers
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Catalyzed by Lewis acids, donor-acceptor cyclopropane 1,1-diesters reacted with enol silyl ethers to afford 1,6-dicarbonyl compounds in moderate to excellent yields. This supplied a mild carbon-carbon bond-forming method from the ring opening of cyclopropanes. A smooth tandem [3+2] cycloaddition/ring opening process has been clearly proved by an independent experiment.
- Fang, Jie,Ren, Jun,Wang, Zhongwen
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supporting information; body text
p. 6659 - 6662
(2009/04/07)
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- Chiral and achiral lithium amides having a fluorous ponytail: Preparation and evaluation as a recycling reagent for lithium enolate generation
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Diisopropylamine derivatives bearing a perfluoroalkyl chain were prepared and converted to the corresponding lithium amides by treatment with n-butyllithium. The fluorous lithium amides reacted with ketones to efficiently produce lithium enolates. Asymmetric deprotonation of prochiral ketones was also studied using lithium amides derived from chiral fluorous amines, which gave optical yields comparable with the parent nonfluorous chiral lithium amides. These reusable fluorous amines can be easily recovered by liquid-liquid extraction or chromatographic separation. Georg Thieme Verlag Stuttgart.
- Matsubara, Hiroshi,Maeda, Louis,Sugiyama, Hiroyuki,Ryu, Ilhyong
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p. 2901 - 2912
(2008/03/13)
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- Bismesitylmagnesium: A thermally stable and non-nucleophilic carbon-centred base reagent for the efficient preparation of silyl enol ethers
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Bismesitylmagnesium has been established as an accessible, practical, convenient, and non-nucleophilic carbon-centred base reagent for efficient access to silyl enol ethers from a series of ketone substrates at readily utilisable temperatures. The Royal Society of Chemistry.
- Kerr, William J.,Watson, Allan J. B.,Hayes, Douglas
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p. 5049 - 5051
(2008/09/17)
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- Synthesis of 5-substituted 4,5,6,7-tetrahydroindoles from cyclohexanones
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5-Substituted 4,5,6,7-tetrahydroindoles were prepared from 4-substituted cyclohexanones in three steps: conversion to an enol silyl ether, introduction of a formylmethyl group at 2-C, and the Paal-Knorr pyrrole synthesis by reacting the 1,4-dicarbonyl compounds with ammonia. The substituents are H, methyl, ethyl, tert-butyl, methoxy, and phenyl.
- Lee, Chang Kiu,Lee, In-Sook Han,Noland, Wayland
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p. 419 - 428
(2008/02/09)
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- Domino Mukaiyama-Michael reactions in the synthesis of polycyclic systems
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Good results were obtained in the Mukaiyama-Michael reaction of the silyl enol ether of cyclohexanone with 2-methyl-2-cyclopentenone and carvone, with transfer of the silyl group to the receiving enone and with TrSbCl6 as catalyst. A second Mukaiyama-Michael reaction of this new silyl enol ether with methyl vinyl ketone and cyclization of the resulting adduct leads to tricyclic compounds in one-pot domino sequences. The scope and limitations of this domino reaction have been investigated.
- Sarabèr, Florence C. E.,Dratch, Svetlana,Bosselaar, Geke,Jansen, Ben J. M.,De Groot, Aede
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p. 1717 - 1725
(2007/10/03)
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- New method for the synthesis of 2-aza-1,3-butadienes
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2-Aza-1,3-butadienes have been synthesized from carbonyl compounds and 1,1,1,3,3,3-hexamethyl-disilazane in the presence of cobalt-containing catalysts. The best yields (up to 95%) were achieved in the case of aldehydes branched in the α-position and 2-methylcyclohexanone. In the case of two α,β-unsaturated ketones, pyridine derivatives were found as the main products. Copyright Taylor & Francis Group, LLC.
- Sisak, Attila
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p. 3693 - 3702
(2007/10/03)
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- The preparation and reaction of enolates within micro reactors
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Over the past 5 years, interest in the miniaturisation of chemical synthesis has grown rapidly, however in order to facilitate transfer of the technology from its current position as a research tool to industrial applications, a core understanding of the challenges associated with transferring reactions from the macro to the micro domain is required. This paper therefore aims to broach this problem by investigating the application of micro reactors to a range of commonly employed synthetic reactions including acylation, aldol, alkylation, 1,4-conjugate addition (Michael addition) and the Knoevenagel condensation. Comparison of the results obtained with traditional batch techniques enable us to highlight some of the advantages associated with micro reaction technology.
- Wiles, Charlotte,Watts, Paul,Haswell, Stephen J.,Pombo-Villar, Esteban
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p. 10757 - 10773
(2007/10/03)
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- Yb(OTf)3-TMSCl, a novel catalytic system in cross-aldol reactions
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A combination of Yb(OTf)3 and TMSCl influenced the outcome of cross-aldol reactions of cycloalkanones and benzaldehyde. Interestingly, reaction of cycloheptanone and cyclooctanone with aldehydes under the Yb(OTf)3- TMSCl reagent system provides 3-(2-oxocycloalkyl)-3- phenylpropanals in conjunction with the corresponding aldol products.
- Kagawa, Natsuko,Toyota, Masahiro,Ihara, Masataka
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p. 655 - 657
(2007/10/03)
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- SAR studies of 3-cyclopropanecarbonyloxy-2-cyclohexen-1-one as inhibitors of 4-hydroxyphenylpyruvate dioxygenase
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Various 3-cyclopropanecarbonyloxy-2-cyclohexen-1-one 1 derivatives have been synthesized and tested as inhibitors of 4-hydroxyphenylpyruvate dioxygenase (4-HPPD) from pig liver. The inhibition results indicated that well-positioned dicarbonyl groups as well as the cyclopropyl group of 1 were essential for potent inhibition. Substitution at the 2-position of the ring system has a significant effect on inhibitor potency, while the 5-position can undergo substantial variations and retain inhibitor potency. In the compounds examined, 2-chloro substituted 12 is the best inhibitor of all with IC50 of 15 nM, the rest of the synthesized analogues were less potent inhibitors than the parent compound.
- Lin, Yung-Lung,Wu, Chung-Shieh,Lin, Shean-Woei,Huang, Jian-Lin,Sun, Yang-Sheng,Yang, Ding-Yah
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p. 685 - 690
(2007/10/03)
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- Intramolecular TiCl4-mediated cyclization reaction of β-hydroxyalkynyl acetals
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Intramolecular TiCl4-mediated cyclization reaction of 1,1-dimethoxy-3-hydroxy-hex-5-yne derivatives produced anti-1-hydroxy-3-methoxy-cyclohex-5-ene derivatives with high diastereoselectivity via antiperiplanar manner on pseudo six-membered chair like conformation (transition state A).
- Kim, Yong-Hyun,Lee, Kee-Young,Oh, Chang-Young,Yang, Jae-Gwon,Ham, Won-Hun
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p. 837 - 841
(2007/10/03)
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- The regioselective preparation of 1,3-diketones
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The regioselectivity of the acylation of Li enolates and silyl enol ethers is reported using acyl halides and acyl cyanides. We illustrate a simple method for the preparation of 1,3-diketones via the silyl enol ether in excellent yields, free from competing O-acylation and diacylation products.
- Wiles, Charlotte,Watts, Paul,Haswell, Stephen J.,Pombo-Villar, Esteban
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p. 2945 - 2948
(2007/10/03)
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- Quantum chemical calculations on the Peterson olefination with α-silyl ester enolates
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The reaction of stabilized Peterson reagents (α-silyl ester enolates) with ketones has been studied theoretically and experimentally. Enolate geometry was studied by trapping experiments and NMR spectroscopy and was found to differ markedly with the nature of the base (LiHMDS vs LDA vs KHMDS). The chelating effect of the lithium counterion was found to be critical for the reaction. For the two ketones studied, the combined weight of experimental and computational data assigns geometrical selectivity to the initial addition transition state, though in general there appears to be a fine balance between three possible choices for the rate-determining step.
- Gillies, Malcolm B.,Tonder, Janne E.,Tanner, David,Norrby, Per-Ola
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p. 7378 - 7388
(2007/10/03)
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- Preparation of silyl enol ethers using (bistrimethylsilyl)acetamide in ionic liquids
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(matrix presented) Ionic liquids have been used for the preparation of silyl enol ethers from aldehydes and ketones with (bistrimethylsilyl)acetamide (BSA) in good yields.
- Smietana, Michael,Mioskowski, Charles
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p. 1037 - 1039
(2007/10/03)
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- Addition reaction of imidazoles and thiazoles with silyl enol ethers in the presence of alkyl chloroformate
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Silyl enol ethers and ketene silyl acetals reacted with imidazole, thiazole, and their benzo derivatives in the presence of an alkyl chloroformate to give 2-substituted imidazolines and thiazolines in good yields via the intermediacy of unstable N-acylated quaternary salts of azoles. In addition, it was found that silyl enol ethers formed in situ were also useful for the reaction to afford the adducts only by simple sequential addition of five commercially available reagents. (C) 2000 Elsevier Science Ltd.
- Itoh, Takashi,Miyazaki, Michiko,Nagata, Kazuhiro,Ohsawa, Akio
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p. 4383 - 4395
(2007/10/03)
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- Discovery of a potent, non-triketone type inhibitor of 4-hydroxyphenylpyruvate dioxygenase
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3-Cyclopropanecarbonyloxy-2-cyclohexen-1-one has been found to be a new, potent, low molecular weight non-triketone type inhibitor of 4-hydroxyphenylpyruvate dioxygenase with IC50 value of 30 nM. Preliminary studies suggest that the two carbonyl groups present in the compound are crucial for the inhibition activity. (C) 2000 Elsevier Science Ltd. All rights reserved.
- Lin, Shean-Woei,Lin, Yun-Loung,Lin, Tzu-Ching,Yang, Ding-Yah
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p. 1297 - 1298
(2007/10/03)
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- Facile synthesis of silyl enol ethers by Mg-promoted coupling of aliphatic carbonyl compounds with trimethylsilyl chloride
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Treatment of aliphatic carbonyl compounds with trimethylsilyl chloride with Mg turning for Grignard reaction without any pre-treatment in N,N- dimethylformamide at room temperature brought about highly facile, effective and stereoselective coupling to give the corresponding silyl enol ethers in good yields.
- Ishino, Yoshio,Kita, Yoshio,Maekawa, Hirofumi,Ohno, Toshinobu,Yamasaki, Yasuhiro,Miyata, Toshiyuki,Nishiguchi, Ikuzo
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p. 1349 - 1352
(2007/10/03)
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- Magnesium bis(diisopropylamide), a useful reagent for regio- and stereoselective synthesis of kinetic silyl enol ethers
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Less highly substituted silyl enol ethers are regiospecifically prepared in high yield, around room temperature under kinetic conditions, from unsymmetrical cyclic ketones and magnesium bis(diisopropylamide) [(DA)2Mg] in THF/heptane. This high regioselectivity is markedly higher than these reported for bromomagnesium diisopropylamide (DAMgBr); it is also similar to this of LDA/DME at -78°C, but (DA)2Mg can be used at room temperature. In addition, a high E-enolization stereoselectivity is observed for benzylic ketones, reverse of this obtained with LDA.
- Lessene, Guillaume,Tripoli, Regis,Cazeau, Philippe,Biran, Claude,Bordeau, Michel
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p. 4037 - 4040
(2007/10/03)
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- Regioselective α-alkylation of silyl enolates using a mild catalyst- ZnCl2 doped on acidic alumina
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ZnCl2 doped acidic alumina used as a solid support acts as a better Lewis acid in the S(N)1 reaction of trimethyl silyl enol ethers with 30, allylic and benzylic halides to yield exclusively the substituted product in excellent yields. This method has been employed for the synthesis of monocyclic sesquitepene hydrocarbon, (+)-β-bisabolene and a monoterpene, 2,6-dimethyl-7-octen-4-one.
- Kad,Singh, Vasundhara,Khurana, Anupam,Chaudhary, Sangeeta,Singh, Jasvinder
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p. 3439 - 3442
(2007/10/03)
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- Eu(fod)3 and SnCl4-catalyzed heterocycloadditions of O-silyl enol ethers deriving from cyclic ketones
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O-t-Butyldimethylsilyl enol ethers deriving from simple cyclic ketones acted as efficient dienophiles in the Lewis acid-catalyzed heterocycloadditions with methyl benzylidenepyruvate 1. Good selectivities were observed with cyclohexanone derivatives. Using Eu(fod)3, the dienophile 2b led to the expected endo adduct 3b (93-97%). When using SnCl4, the major product (89-95%) was found to be the 'abnormal' adduct 5b with a trans ring junction.
- Dujardin, Gilles,Martel, Arnaud,Brown, Eric
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p. 8647 - 8650
(2007/10/03)
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- Mukaiyama aldol and Michael reactions catalyzed by lanthanide iodides
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Samarium diiodide is an efficient catalyst precursor which allows the formation of condensation products between various carbonyl compounds and ketene silyl acetals or enoxysilanes. With α,β-unsaturated carbonyl compounds, 1,2- or 1,4-additions are observed according to the structure of the substrate. α,β-Unsaturated ketones yield to enoxysilanes by selective Michael additions. Aldol products are isolated as silyl ethers. The mechanisms of the reactions are discussed.
- Giuseppone, Nicolas,Van De Weghe, Pierre V.,Mellah, Mohamed,Collin, Jacqueline
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p. 13129 - 13148
(2007/10/03)
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