- VINYL COPPER DERIVATIVES 30. REACTIVITY OF γ-SILYLATED VINYL COPPER REAGENTS
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γ-silylated vinyl copper reagents react with elecrtophiles with total retention of configuration of the C=C double bond.Oxidation, allylation, vinylation and acylation lead to functionalized dienes with a given geometry.
- Foulon, J. P.,Bourgain-Commercon, M.,Normant, J. F.
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- Tandem 1,4-addition reactions with benzene and alkylated benzenes promoted by pentaammineosmium(II)
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Electrophiles such as dimethoxymethane and 3-penten-2-one react with the complex [Os(NH3)5-(η2-benzene)]2+ in the presence of triflic acid to form metastable benzenium intermediates. These benzenium intermediates further react with carbon nucleophiles including silyl ketene acetals, (silyloxy)alkenes, and phenyllithium in an overall tandem 1,4-addition sequence. The metal fragment controls the relative stereo- and regiochemistry for both electrophilic and nucleophilic addition steps. Upon oxidative demetalation with silver triflate, cis-1,4 cyclohexadienes are formed in yields ranging from 16 to 82%. This methodology can also be used to dearomatize toluene and ortho- and meta-xylene with unexpectedly high regio- and stereocontrol.
- Ding, Fei,Kopach, Michael E.,Sabat, Michal,Harman, W. Dean
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- New C3v-symmetrical tribenzotriquinacenes bearing extended and oxy-functionalised alkyl groups at their benzhydrylic bridgeheads
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A series of tribenzotriquinacene derivatives bearing three oxy-functionalised alkyl groups at the benzhydrylic bridgeheads (C-4b, C-8b and C-12b) have been synthesised. The 4b,8b,12b-triallyl derivative was used to generate the corresponding TBTQ-tris-acetaldehyde and TBTQ-tris(acetic acid), in which the functional groups stretch out from the convex rigid molecular surface. The corresponding tribromo derivate was found to undergo smooth Lewis acid-catalyzed C-C coupling with appropriate silyl enol ethers to afford a series of threefold 4b,8b,12b-(2-oxoalkyl)-substituted tribenzotriquinacenes. Six-fold nitration at the arene periphery was performed with 4b,8b,12b-tripropyltribenzotriquinacene and with the TBTQ-tris(acetic acid) to check for the effect of the bridgehead groupings as solubilising auxiliaries.
- Mughal, Ehsan U.,Kuck, Dietmar
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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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- Synthesis of Bridged Azacycles and Propellanes via Nitrene/Alkyne Cascades
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A nitrene/alkyne cascade reaction terminating in C-H bond insertion to form functionalized bridged azacycles from carbonazidates is presented. Due to an initial Huisgen cyclization, all carbonazidates reacted with the alkyne in an exo mode in contrast to the use of sulfamate esters, which react predominately in an endo mode. Substrates with different ring sizes as well as different aryl and heteroaryl groups were also explored. Variation of the nitrene tether showed that 7-membered rings were the maximum ring size to be formed by nitrene attack on the alkyne. Examples incorporating stereocenters on the carbonazidate's tether induced diasteroselectivity in the formation of the bridged ring and two new stereocenters. Additionally, propellanes containing aminals, hemiaminals, and thioaminals formed from the bridged azacycles in the same reaction via an acid-promoted rearrangement.
- May, Jeremy A.,Wang, Qinxuan
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supporting information
p. 3039 - 3044
(2020/04/20)
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- Enantioselective N-Heterocyclic Carbene Catalyzed Synthesis of Functionalized Indenes
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An enantioselective NHC (N-heterocyclic carbene) catalyzed synthesis of indenes from bifunctional α,β-unsaturated acyl fluorides and TMS enol ethers has been discovered. The reaction has broad generality (31 examples) and proceeds with high levels of enantioselectivity (most >92:8 er). Mechanistically the reaction likely occurs via a Michael/β-lactonization/decarboxylation sequence. Derivatization studies and limitations are discussed.
- Zhang, Changhe,Lupton, David W.
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supporting information
p. 4456 - 4459
(2017/09/11)
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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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- 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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- A NEW PRACTICAL SYNTHESIS OF SILYL ENOL ETHERS. PART.I. FROM SIMPLE ALDEHYDES AND KETONES.
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A new, practical route to enoxysilanes is described from simple enolizable aldehydes or ketones, using the trimethylchlorosilane-sodium iodide-tertiary amine reagent in acetonitrile.From certain aldehydes, an onium intermediate has been isolated.A conformational study of this onium intermediate and a thermal unimolecular syn-elimination process may explain the stereoselectivity of the reaction.Such an interpretation can be extended to all the aldehydes and ketones considered.Steric factors related to the nature both of the cabonyl derivative and of the amine play a capital role for the regio- as well as for the stereo-control of the reaction.
- Cazeau, P.,Duboudin, F.,Moulines, F.,Babot, O.,Dunogues, J.
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p. 2075 - 2088
(2007/10/02)
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- Enol Ethers, XVII. Acylation of Trimethylsilyl Enol Ethers with Malonyl Dichloride - Synthesis of 4-Hydroxy-2H-pyran-2-ones
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Trimethylsilyl enol ethers of aldehydes 1, acyclic and cyclic ketones 4 and 10, respectively, are acylated by malonyl dichloride (2) at room temperature or even at -60 deg C.After aqueous workup, the 6-unsubstituted 4-hydroxy-2H-pyran-2-ones 3 are obtained from 1-(trimethylsiloxy)alkenes 1, whereas the 5,6-alkylene-bridged 4-hydroxy-2H-pyran-2-ones 11 are formed from 1-(trimethylsiloxy)cycloalkenes 10.Acylation of 2-(trimethylsiloxy)-1-propene (4a) and 3-(trimethylsiloxy)-2-pentene (4b) results in mixtures of 4-(trimethylsiloxy)-2H-pyran-2-ones 5 (main products) and phloroglucinol tris(trimethylsilyl) ethers (6) (by-products).
- Effenberger, Franz,Ziegler, Thomas,Schoenwaelder, Karl-Heinz,Kesmarszky, Thomas,Bauer, Bernd
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p. 3394 - 3404
(2007/10/02)
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- NOUVELLE SYNTHESE REGIOSELECTIVE DE β-ALCOXYCETONES A PARTIR D'ENOXYSILANES ET DE TRISENOXYSILANES ENGENDRES in situ
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An easy, regiospecific, route to β-alkoxyketones based on the use of methyl trichlorosilane for in situ generation of α-chloroethers and trisenoxysilanes is described.
- Rochin, Christophe,Babot, Odile,Duboudin, Francoise
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p. C24 - C28
(2007/10/02)
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- Palladium Catalyzed Reaction of Trimethylsilyltributyltin with α-Halo Ketones. Preparation of Enol Silyl Ethers
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The reaction of trimethylsilyltributyltin with α-halo ketone in the presence of a catalytic amount of palladium chloride plus twice molar amounts of trimethyl phosphite gave enol silyl ethers in good yields.
- Kosugi, Masanori,Ohya, Takao,Migita, Toshihiko
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p. 3539 - 3540
(2007/10/02)
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- Reactions of Trialkylsilyl Trifluoromethanesulfonates, I. - Synthesis of Trialkylsilyl Enol Ethers
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The reactions of the ketones 2,2-bromoketones 6, α,β-unsaturated ketones 8, 1,2-diketones, and aliphatic aldehydes 20 with trialkylsilyl triflates 1 in the presence of triethylamine (4) at room temperature yield the silyl enol ethers 3, 7, 9, 11, and 21.The silylation of the unsymmetrical ketones 12 with 1a/4 runs regioselectively in the thermodynamical sense using 1a/12 in excess and yields the enol ethers 13t.The course of this reaction is discussed briefly.
- Emde, Herbert,Goetz, Andreas,Hofmann, Karin,Simchen, Gerhard
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p. 1643 - 1657
(2007/10/02)
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- Chemistry of enol ethers. LI. Reaction of vinyl silyl ethers with orthoformic esters
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The silyl ethers of enolic forms of ketones react with orthoformates in the presence of zinc chloride at catalyst to form β-ketoacetals.The analogous reaction with the silyl ethers of enolic forms of aldehydes leads to the formation of the tetraacetals of 1,3-dialdehydes.
- Makin, S. M.,Kruglikova, R. I.,Popova, T. P.,Tagirov, T. K.
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p. 630 - 634
(2007/10/02)
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- SUR L'OBTENTION HAUTEMENT REGIO- ET STEREOSELECTIVED'ENOXYSILANES PAR ACTION DU BIS(TRIMETHYLSILYL)ACETAMIDE EN MILIEU HMPT SUR LESS DERIVES CARBONYLES ENOLISABLES
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The authors describe a new and general method for the preparation of enoxysilanes by silylation of enolizable aldehydes and ketones by use of bis(trimethylsilyl)acetamide in HMPT, in the presence of very small quantities of sodium metal(or another basic a
- Dedier, James,Gerval, Pierre,Frainnet, Emile
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p. 183 - 198
(2007/10/02)
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- METHODE SIMPLE POUR LA SYNTHESE RAPIDE ET STEREOSELECTIVE D'ENOXYSILANES D'ALDEHYDES ET DE CETONES
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A new highly regio- and stereo-selective method for the preparation of enoxysilanes, viz. treatment of Me3SiCl, NaI, Et3N with enolizable aldehydes and ketones is described.
- Cazeau, Philippe,Moulines, Francoise,Laporte, Odile,Duboudin, Francoise
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