The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Hélène Lebel - One of the best experts on this subject based on the ideXlab platform.
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Transition-metal-catalyzed chemoselective Methylenation of dicarbonyl substrates.
The Journal of organic chemistry, 2008Co-Authors: Hélène Lebel, Michaël Davi, Grzegorz T. StoklosaAbstract:Rhodium- and copper-catalyzed Methylenation reactions with trimethylsilyldiazomethane, triphenylphosphine, and 2-propanol were used to react chemoselectively with aldehydes, alkoxymethylketones, and trifluoromethylketones in substrates also containing a less reactive carbonyl group. Terminal alkenes were obtained in high yields, and no protecting group was necessary in the Methylenation process.
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Copper-catalyzed Methylenation reaction: total synthesis of (+)-desoxygaliellalactone.
Organic letters, 2007Co-Authors: Hélène Lebel, Michael ParmentierAbstract:The enantioselective total synthesis of (+)-desoxygaliellalactone was achieved in six steps starting from 4-tert-butyldimethylsilyloxybutanal. This synthesis featured a one-pot copper-catalyzed Methylenation−Diels−Alder cyclization. The challenging Methylenation of aldehyde 4 was studied under various reaction conditions. Whereas Wittig reaction conditions led to byproducts resulting from decomposition of the sensitive butenolide moiety, the mild copper-catalyzed Methylenation reaction produced the desired triene in good yield.
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copper catalyzed Methylenation reaction total synthesis of desoxygaliellalactone
Organic Letters, 2007Co-Authors: Hélène Lebel, Michael ParmentierAbstract:The enantioselective total synthesis of (+)-desoxygaliellalactone was achieved in six steps starting from 4-tert-butyldimethylsilyloxybutanal. This synthesis featured a one-pot copper-catalyzed Methylenation−Diels−Alder cyclization. The challenging Methylenation of aldehyde 4 was studied under various reaction conditions. Whereas Wittig reaction conditions led to byproducts resulting from decomposition of the sensitive butenolide moiety, the mild copper-catalyzed Methylenation reaction produced the desired triene in good yield.
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Reductive one-carbon homologation of aldehydes and ketones.
The Journal of organic chemistry, 2005Co-Authors: Hélène Lebel, Chehla LadjelAbstract:[reaction: see text] A rhodium-catalyzed Methylenation-hydrogenation cascade process allows the homologation of carbonyl compounds to lead to the corresponding alkanes in high yields.
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rhodium catalyzed cascade reactions a Methylenation hydroboration homologative process
Journal of Organometallic Chemistry, 2005Co-Authors: Hélène Lebel, Chehla LadjelAbstract:Abstract A very efficient rhodium-catalyzed cascade process allowing the transformation of aldehydes and ketones into their corresponding one or two-carbon homologated alcohol products through a Methylenation–hydroboration sequence is reported. Wilkinson’s complex is used to catalyze both reactions in a one-pot procedure that does not require the isolation of the alkene intermediate.
Andrew B. Holmes - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of medium-ring lactones via tandem Methylenation/Claisen rearrangement of cyclic carbonates
Chemical Communications, 2000Co-Authors: Davidson James Edward Paul, Edward Anderson, Wilm Buhr, Justin R. Harrison, Paul T. O'sullivan, Ian Collins, Richard H. Green, Andrew B. HolmesAbstract:Tandem Methylenation/Claisen rearrangement of cyclic carbonates derived from vinyl-substituted 1,3- and 1,4-diols afforded eight and nine-membered unsaturated lactones respectively.
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synthesis of medium ring lactones via tandem Methylenation claisen rearrangement of cyclic carbonates
Chemical Communications, 2000Co-Authors: James Edward Paul Davidson, Edward Anderson, Wilm Buhr, Justin R. Harrison, Ian Collins, Richard H. Green, Paul T Osullivan, Andrew B. HolmesAbstract:Tandem Methylenation/Claisen rearrangement of cyclic carbonates derived from vinyl-substituted 1,3- and 1,4-diols afforded eight and nine-membered unsaturated lactones respectively.
Valérie Paquet - One of the best experts on this subject based on the ideXlab platform.
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Multicatalytic Processes Using Diverse Transition Metals for the Synthesis of Alkenes
Journal of the American Chemical Society, 2004Co-Authors: Hélène Lebel, Valérie PaquetAbstract:A series of cascade processes for the synthesis of alkenes from alcohols is described. Each individual step is catalyzed with a specific transition metal complex. The oxidation−Methylenation one-pot procedure took place in the presence of a palladium and a rhodium catalyst to produce the desired terminal alkenes in high yields. A Methylenation−ring-closing metathesis allowed the synthesis of cyclic alkenes from carbonyl derivatives, using the second-generation metathesis catalyst. Finally, an oxidation−Methylenation−RCM process that involves up to three different transition metal catalysts in the same vessel is presented.
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Highly Efficient Synthesis of Terminal Alkenes from Ketones
Organic letters, 2004Co-Authors: Hélène Lebel, Valérie Paquet, Danielle Guay, Kim HuardAbstract:[reaction: see text] The rhodium(I)-catalyzed Methylenation of ketones using trimethylsilyldiazomethane proceeds to give the corresponding alkenes in good yields (60-97%). The use of an excess of 2-propanol and 1,4-dioxane as a solvent were instrumental to obtain the desired alkenes in high yields. Superior results were achieved with the rhodium(I)-catalyzed Methylenation in comparison with the standard Wittig reaction.
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Highly chemoselective rhodium-catalyzed Methylenation of fluorine-containing ketones.
Organic letters, 2002Co-Authors: Hélène Lebel, Valérie PaquetAbstract:[reaction: see text] The rhodium(I)-catalyzed Methylenation of functionalized fluorinated ketones using trimethylsilyldiazomethane proceeds to give the corresponding fluoromethylalkenes in good yields (61-90%). Remarkable chemoselectivity was observed for the synthesis of keto-substituted organofluorine alkenes.
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Methylenation of aldehydes transition metal catalyzed formation of salt free phosphorus ylides
Angewandte Chemie, 2001Co-Authors: Hélène Lebel, Valérie Paquet, Caroline ProulxAbstract:A variety of terminal alkenes are produced in excellent yields by the rhodium(I)-catalyzed Methylenation of aldehydes using TMSCHN2 and PPh3 [Eq. (1)]. These mild reaction conditions allowed the conversion of enolizable substrates and the chemoselective Methylenation of aldehydes over ketones. TMS=trimethylsilyl.
Kuan-ting Chen - One of the best experts on this subject based on the ideXlab platform.
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meonh2 hcl mediated α Methylenation conjugate addition of α sulfonyl o hydroxyacetophenones with methyl sulfoxides route to 3 sulfonylchroman 4 ones
Synthesis, 2021Co-Authors: Meng-yang Chang, Kuan-ting ChenAbstract:A novel and efficient route for the synthesis of 3-sulfonylchroman-4-ones from α-sulfonyl o-hydroxyacetophenones with methyl sulfoxides via a MeONH2·HCl-mediated sequential Methylenation/ conjugate addition is described. Plausible reaction mechanisms are proposed and discussed. Various reaction conditions for this novel, one-pot, environmentally friendly conversion were investigated.
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MeONH2·HCl-Mediated α-Methylenation/Conjugate Addition of α-Sulfonyl o-Hydroxyacetophenones with Methyl Sulfoxides: Route to 3-Sulfonylchroman-4-ones
Synthesis, 2020Co-Authors: Meng-yang Chang, Kuan-ting ChenAbstract:A novel and efficient route for the synthesis of 3-sulfonylchroman-4-ones from α-sulfonyl o-hydroxyacetophenones with methyl sulfoxides via a MeONH2·HCl-mediated sequential Methylenation/ conjugate addition is described. Plausible reaction mechanisms are proposed and discussed. Various reaction conditions for this novel, one-pot, environmentally friendly conversion were investigated.
Antony J. Fairbanks - One of the best experts on this subject based on the ideXlab platform.
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An approach to the synthesis of α-(1-6)-C-disaccharides by tandem Tebbe Methylenation and Claisen rearrangement
Tetrahedron, 2005Co-Authors: David Chambers, Graham R. Evans, Antony J. FairbanksAbstract:Uronic acids, most efficiently synthesised from the corresponding alcohols by two step Dess-Martin and sodium chlorite mediated oxidation, may be used as coupling partners for esterification with an allo glycal as substrates for the tandem Tebbe/Claisen approach to the synthesis of 1-6 linked C-disaccharides. Whilst esters of glucuronic and mannuronic acids successfully undergo Tebbe Methylenation, esters derived from galacturonic acids are unreactive under these conditions. Thermal Claisen rearrangement of vinyl ethers produced by Methylenation yields α-C-disaccharides with complete control of anomeric stereochemistry.
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Stereoselective synthesis of C-glycosides via Tebbe Methylenation and Claisen rearrangement
Tetrahedron Letters, 2000Co-Authors: H. Yasmin Godage, Antony J. FairbanksAbstract:Abstract A variety of β- C -glycosides may be readily accessed in a stereoselective fashion from 3-OH glycal esters, via the use of Tebbe Methylenation and subsequent thermal Claisen rearrangement. The use of carbohydrate ester substrates allows the formation of β(1→6) linked C -disaccharides.