- Chemoselective allylic addition of allyltrichlorosilane to α- oxocarboxylic acids: Synthesis of tertiary α-hydroxy carboxylic acids
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Allyltrichlorosilane can add to α-oxocarboxylic acids in the presence of DMF and HMPA. The α-carboxylic substituent exerts a remarkable neighboring group effect on the reaction. The reaction presumably proceeds in an intramolecular fashion through a 'rigid' bicyclic transition state assembly involving a hypervalent silicate species, which produces the chemoselectivity approaching 100%. (C) 2000 DuPont Pharmaceuticals Company.
- Wang, Zhe,Xu, Guoyou,Wang, Dengjin,Pierce, Michael E.,Confalone, Pat N.
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- Regio- and stereochemical aspects in synthesis of 2-allyl derivatives of glycolic, mandelic and lactic acids and their iodocyclisations to 3-hydroxy-3,4-dihydrofuran-2(5H)-ones
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Glyoxalic, phenylglyoxalic and pyruvic acids 1a-c undergo regio- and diastereoselective indium mediated allylations with allyl and cinnamyl bromides and ethyl 4-bromocrotonate to provide respective 2-allyl-, 2-(1-phenylallyl)- and 2-[(1-ethoxycarbonyl)all
- Kaur, Pervinder,Singh, Palwinder,Kumar, Subodh
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- The addition of allylboronates to alpha-oxocarboxylic acids
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Allylboronates react with alpha-oxocarboxylic acids to yield tertiary homoallylic alpha-hydroxycarboxylic acids in a highly chemoselective manner. The reaction presumably proceeds via a bicyclic transition state. The alpha-carboxylic substituent enhances
- Wang, Zhe,Meng, Xian-Jun,Kabalka, George W.
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- Chemoselective Carbonyl Allylations with Alkoxyallylsiletanes
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Alkoxyallylsiletanes are capable of highly chemo- and diastereoselective carbonyl allylsilylations. Reactive substrates include salicylaldehydes and glyoxylic acids. Chemoselectivity in these reactions is thought to arise from a mechanism involving first exchange of the alkyoxy group on silicon with a substrate hydroxyl followed by activation of a nearby carbonyl by the Lewis acidic siletane and intramolecular allylation. In this way, substrates containing multiple reactive carbonyl groups (e.g., dialdehyde or triketone) can be selectively monoallylated, even overcoming inherent electrophilicity bias.
- Spaltenstein, Paul,Cummins, Elizabeth J.,Yokuda, Kelly-Marie,Kowalczyk, Tim,Clark, Timothy B.,O'Neil, Gregory W.
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p. 4421 - 4428
(2019/03/26)
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- Practical and Broadly Applicable Catalytic Enantioselective Additions of Allyl-B(pin) Compounds to Ketones and α-Ketoesters
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A set of broadly applicable methods for efficient catalytic additions of easy-to-handle allyl-B(pin) (pin=pinacolato) compounds to ketones and acyclic α-ketoesters was developed. Accordingly, a large array of tertiary alcohols can be obtained in 60 to >98 % yield and up to 99:1 enantiomeric ratio. At the heart of this development is rational alteration of the structures of the small-molecule aminophenol-based catalysts. Notably, with ketones, increasing the size of a catalyst moiety (tBu to SiPh3) results in much higher enantioselectivity. With α-ketoesters, on the other hand, not only does the opposite hold true, since Me substitution leads to substantially higher enantioselectivity, but the sense of the selectivity is reversed as well.
- Robbins, Daniel W.,Lee, KyungA,Silverio, Daniel L.,Volkov, Alexey,Torker, Sebastian,Hoveyda, Amir H.
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supporting information
p. 9610 - 9614
(2016/08/10)
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- Synthesis of tertiary α-hydroxy acids by silylene transfer to α-keto esters
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(Chemical Equation Presented) α-Keto esters can be converted into α-hydroxy acids in a single flask involving metal-catalyzed silylene transfer, 6π-electrocyclization, Ireland-Claisen rearrangement, and hydrolysis. This reaction sequence is stereoselectiv
- Howard, Brett E.,Woerpel
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p. 4651 - 4653
(2008/03/12)
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- Nucleophilic benzoylation using a mandelic acid dioxolanone as a synthetic equivalent of the benzoyl carbanion. Oxidative decarboxylation of α-hydroxyacids
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The synthesis of alkyl aryl ketones using a mandelic acid dioxolanone as a synthetic equivalent (Umpolung) of the benzoyl carbanion is reported. The methodology involves alkylation of the mandelic acid dioxolanone, hydrolysis of the dioxolanone moiety in the alkylated products and oxidative decarboxylation of the resulting α-hydroxyacids. The last step is carried out in a catalytic aerobic way using a Co (III) complex in the presence of pivalaldehyde under very mild conditions.
- Blay, Gonzalo,Fernandez, Isabel,Monje, Belen,Pedro, Jose R.
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p. 365 - 372
(2007/10/03)
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- The efficient allylations of 2-oxocarboxylic acids. Synthesis of 2-allyl derivatives of 2-hydroxycarboxylic acids
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2-Oxocarboxylic acids or their sodium salts undergo indium-mediated allylation with allyl bromide cinnamyl bromide and ethyl 4- bromocrotonate to provide the corresponding 2-allyl derivatives of glycolic lactic mandelic and malic acids. In the case of rea
- Kumar, Subodh,Kaur, Pervinder,Chimni, Swapandeep Singh
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p. 573 - 574
(2007/10/03)
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- Nucleophilic benzoylation using lithiated methyl mandelate as a synthetic equivalent of the benzoyl carbanion. Oxidative decarboxylation of α-hydroxyacids
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The synthesis of alkyl aryl ketones using lithiated methyl mandelate as a synthetic equivalent of the benzoyl carbanion is reported (Umpolung). The methodology involves alkylation of methyl mandelate, hydrolysis of the ester group and oxidative decarboxylation of the resulting α-hydroxyacids. The last step is carried out in a catalytic aerobic way using a Co(III) complex in the presence of pivalaldehyde under very mild and advantageous conditions. The procedure is also applied to methyl mandelates substituted on the aromatic ring.
- Blay, Gonzalo,Fernández, Isabel,Formentin, Pilar,Monje, Belén,Pedro, José R,Ruiz, Rafael
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p. 1075 - 1081
(2007/10/03)
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- Catalytic aerobic oxidative decarboxylation of α-hydroxy-acids. Methyl mandelate as a benzoyl anion equivalent
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The monomeric square-planar cobalt(III) complex of bis-N,N'- disubstituted oxamides catalyses the oxidative decarboxylation of α-hydroxy acids with molecular oxygen/pivalaldehyde with very good yields. This reaction offers an interesting alternative in the use of methyl mandelate as a convenient benzoyl anion equivalent.
- Blay, Gonzalo,Fernandez, Isabel,Formentin, Pilar,Pedro, Jose R.,Rosello, Antonio L.,Ruiz, Rafael,Journaux, Yves
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p. 3327 - 3330
(2007/10/03)
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- Palladium-catalyzed allylation of α-hydroxy acids
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Mandelic and lactic acids are converted to the 1,3-dioxolan-4-ones by treatment with acetone dimethyl acetal.Deprotonation followed by treatment with an allyl acetate and a catalytic amount (1 mol percent) of palladium catalyst afforded the allylated dioxolanones, which could be hydrolyzed to the corresponding α-allyl α-hydroxy acids.The lithium enolate of the dioxolanone of mandelic acid was also coupled with methallyl, cinnamyl, geranyl and (E)-1-methyl-2-butenyl acetates.The zinc enolate of the dioxolanone of lactic acid reacted smoothly with allyl acetate in a catalyzed reaction whereas no detectable reaction was observed when the lithium enolate was used.This appears to be the result of complications arising from the enhanced basicity of the lithium compared to zinc enolate.Various attempts were made to achieve enantioselectivity using chiral ligands on the palladium catalyst.The zinc enolates were found to provide better results although the enantioselectivity was only modest, about 30percent enantiomeric excess being the best result obtained.Chiraphos proved to be the best optically active ligand of a variety tested.
- Moorlag, Henk,Vries, Johannes G. de,Kaptein, Bernard,Schoemaker, Hans E.,Kamphuis, Johan,Kellogg, Richard M.
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p. 129 - 137
(2007/10/02)
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