- Preparation and reactions of functionalized magnesium carbenoids
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New functionalized magnesium carbenoids bearing an ester function have been prepared via an iodine-magnesium exchange reaction. These new carbenoids react with various electrophiles (60-88% yield). A substituted magnesium carbenoid has been prepared by su
- Avolio, Salvatore,Malan, Christophe,Marek, Ilan,Knochel, Paul
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p. 1820 - 1822
(2007/10/03)
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- Thioalkylation of Enolates, III. Stereoselective Synthesis of Steroids and Related Compounds, II. α-Thioalkylation of Zinc Dienolates to 4-Substituted 1-tert-Butoxy-7a-methyl-hexahydroinden-5-ones
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α-Alkylation of the α,β-unsaturated ketone 1 at C-4 has been achieved by thioalkylation of the corresponding zinc dienolate with α-chlorosulfides of type 2.The desulfurization of the β-(phenylthio)ketones 4 leads directly to the 4-substituted hexahydroind
- Groth, Ulrich,Koehler, Thomas,Taapken, Thomas
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p. 665 - 668
(2007/10/02)
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- Thioalkylation of Enolates, IV. α-Alkylidenecyclopentanones by α-Alkylidation of Methyl 2-Oxocyclopentanecarboxylate
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An α-alkylidation of cyclopentanone was achieved in two reaction steps in an overall yield of 20 to 79percent via a zinc chloride-catalyzed thioalkylation of the zinc enolate of methyl 2-oxocyclopentanecarboxylate (3) and subsequent saponification/desulfurization of the β-(phenylthio) ketone intermediates 5.For the saponification/desulfurization step DABCO proved to be the reagent of choice and superior to the use of alkali or magnesium halides. - Key Words: Zinc enolates, thioalkylation of / Cyclopentanones, α-alkylidene
- Arnecke, Ralf,Groth, Ulrich,Koehler, Thomas
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p. 891 - 894
(2007/10/02)
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- Thioalkylation of Enolates, II. α-Thioalkylation of Zinc Enolates to α,α-Disubstituted Ketones
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An α-alkylation of the 2-methylcycloalkanones 1 and 4 at the higher substituted carbon can be achieved by thioalkylation of the corresponding zinc enolates with the α-chlorosulfides 3.The desulfurization can be carried out with either Raney nickel or lithium in diethylamine for compounds which contain double or triple bonds. Key Words: Zinc enolates, thioalkylation of / Ketones, α,α-disubstituted / Desulfurization
- Groth, Ulrich,Huhn, Thomas,Richter, Norbert
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- ZINC(II)-CHLORIDE INDUCED THIOALKYLATION OF ALUMINIUM ENOLATES; ENANTIOSELECTIVE SYNTHESIS OF ESTRADIOL-3-METHYL-17-tert-BUTYL DIETHER
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Zinc(II)-chloride induced thioalkylation of the aluminium enolate 6 generated by conjugate reduction of the enone 5 leads - directly or via its trimethylsilylenol ether 6 - to alkylated hydrindanones 10 which are important intermediates in the synthesis o
- Groth, Ulrich,Koehler, Thomas,Taapken, Thomas
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p. 7583 - 7592
(2007/10/02)
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- α-ALKYLATION AND α-ALKYLIDENATION OF CARBONYL COMPOUNDS BY O-SILYLATED ENOLATE PHENYLTHIOALKYLATION
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For many reactions next to a carbonyl group, the use of O-silylated enolate chemistry offers improvements in yield and selectivity over the corresponding reactions of Group I metal enolates.In the case of α-alkylation of carbonyl compounds, Lewis acid (TiCl4 or ZnBr2) promoted phenylthioalkylation of O-silylated enolates 3 by α-chlorosulphides 4 (R3=H, Me, Prn, Pri, Bui, and Me3Si), followed by reductive sulphur removal by Raney nickel, 5->6, is found to be a reliable method for this synthetically important C-C bond forming step.An alternative sulphur elimination pathway via the sulphoxide, 5->7, allows the regio- and stereocontrolled α-alkylidenation of carbonyl compounds.The phenylthioalkylation reaction is applicable to ketones, aldehydes, esters, and lactones.
- Paterson, Ian
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p. 4207 - 4220
(2007/10/02)
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- Stereochemical studies on the formation of α,β-epoxysulfones using α-chloro-β-hydroxysulfones of known configuration
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Substitution reactions adjacent to sulfonyl groups are known to proceed with difficulty, and there is evidence to suggest that these may not necessarily proceed by an SN2 pathway.The mechanism of these reactions could be studied in principle by using the conversion of α-chloro-β-hydroxysulfones of known configuration into α,β-epoxysulfones of known configuration.This paper describes results in which this has been attempted.However, the stereochemical aspects of the epoxide formation could not be assigned unequivocally because of the intervention of a very facile "retro-aldol" process when the chlorohydrins are subjected to treatment with bases, although the experimental results do suggest that the reaction does proceed in a regular SN2-like manner, with inversion at carbon.The X-ray crystal structures of two highly substituted α,β-epoxysulfones are presented, thus putting the structures, including stereochemistry, of a range of these compounds of firm ground.
- Grossert, J. Stuart,Sotheeswaran, Subramanian,Dharmarante, H. Ranjith W.,Cameron, T. Stanley
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p. 2870 - 2879
(2007/10/02)
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- A VERSATILE VINYL SULPHIDE SYNTHESIS USING BENZENESULPHENYL CHLORIDE
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Benzenesulphenyl chloride (PhSCl) in CH2Cl2 at -78 deg C converts thioacetals and thioketals to their α-chlorosulphides which afford vinyl sulphides on elimination.The method is compatible with a range of funcionality.
- Bartels, Birgit,Hunter, Roger,Simon, Clive D.,Tomlinson, Geoffrey D.
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p. 2985 - 2988
(2007/10/02)
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- Synthesis and Reaction of α(Dimethylamino)alkanal Dimethylhydrazones
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Several α(dimethylamino)aldehyde hydrazones of the general structure 11 have been obtained by alkylation of the lithium salt of 9 or by addition of Grignard reagents to 15 or 17.The compounds react with acyl chlorides to give hydrazones of unsaturated aldehydes.The same products 27 are obtained by thermal degradation of the ammonium salts 26.In the hydrazonoammonium salts 26a, g the trimethylammonium group can be substituted by a variety of nucleophiles (--> 34-39).
- Habernegg, Renate,Severin, Theodor
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p. 2397 - 2413
(2007/10/02)
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- A New Syntethic Route to Vinyl Sulfides Utilizing the Reaction of (Phenylthio)carbenes with Nitrile Anions
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Reactions of nitrile anion (LiCR2R3CN) and (phenylthio)carbenes generated from 1-chloroalkyl phenyl sulfides (R1CH(Cl)SPh) 2a-e by the action of n-BuLi have been shown to be a useful synthetic route to vinyl sulfides (PhSC(R1)=CR2R3) 3a-k (34-91percent).The nucleophilic attack of the nitrile anion on the carbenic species gave the presumed intermediate β-(phenylthio)-β-lithionitrile, which eliminated LiCN to give the expected vinyl sulfides.The application of the present reaction to the synthesis of cyclic vinyl sulfides was successful: the decomposition of the dianion ofω,ω-bis(phenylthio)alkanenitriles (8b, 8c, 11, and 14) affording the corresponding 1-(phenylthio)cycloalkenes (9, 10, 12, and 15) in 12-87percent yields.
- Harada, Toshiro,Karasawa, Akio,Oku, Akira
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p. 842 - 846
(2007/10/02)
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- DIRECT CONVERSION OF ALKENES INTO METHYL-SUBSTITUTED CYCLOPROPANES USING AN ORGANOIRON ETHYLIDENE TRANSFER REAGENT
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(η5-C5H5)(CO)2FeCH(CH3)SPh (8) serves as a quite useful reagent for the transfer of ethylidene groups to alkenes to give methyl-substituted cyclopropanes in good yields.The reaction is accomplished by allowing 8 to react with an alkylating agent such as trimethyloxonium tetrafluoroborate or methyl fluorosulfonate in the presence of the alkene substrate.The active ethylidene transfer reagent is apparently a sulfonium salt which is too reactive to be isolated under normal conditions.In all csases, cyclopropanes are obtained stereospecifically with respect to the configuration of the starting alkenes, and with certain classes of substrates such as cis-disubstituted alkenes, the reaction also occurs with very high syn-stereoselectivity.
- Kremer, Kenneth A. M.,Helquist, Paul
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p. 231 - 252
(2007/10/02)
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- DIVINYL SULFIDE. XI. 1-CHLOROVINYL AND 1-CHLOROETHYL SULFIDES
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Di(1,2-dichloroethyl) sulfide is dehydrochlorinated by the action of amines or potassium hydroxide and methanol with the formation of 1,2-dichloroethyl 1-chlorovinyl and di(1-chlorovinyl) sulfides.The best dehydrochlorinating reagents are dimethylaniline
- Amosova, S. V.,Gostevskaya, V. I.,Gavrilova, G. M.,Enikeeva, E. I.,Trofimov, B. A.
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p. 2294 - 2298
(2007/10/02)
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- Stereospecific Rearrangement of 2,2-Disubstituted Vinylsilane Epoxides to the Silyl Enol Ethers of 2,2-Disubstituted Aldehydes
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The Z- and E-2-ethyl-2-methylvinylsilane epoxides (5a) and (5b) rearrange stereospecifically in the presence of boron trifluoride-diethyl ether to the Z- and E-silyl enol ethers, (6a) and (6b), respectively, of 2-methylbutanal.These silyl enol ethers reac
- Fleming, Ian,Newton, Trevor W.
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p. 119 - 124
(2007/10/02)
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