Hydroboration. XXII. The Reaction of Unsaturated Esters with Diborane and Disiamylborane

Brown, Herbert C.; Keblys, Kestutis A.

doi:10.1021/ja01063a029

Cited by 56 publications

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“…This was done by hydroboration of ethyl crotonate since the hydroboration reaction has been found to lead to the addition of the elements of water to a double bond with a high degree of stereospecificity. It has been shown in the few cases where A"-unsaturated esters were subjected to hydroboration that reduction of the ester group occurs as the predominant side reaction [4,5]. However, ethyl 3-hydroxypropionate has been prepared in 9 % yield from ethyl acrylate [4].…”

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confidence: 99%

Substrate Stereochemistry of the Enoyl‐CoA Hydratase Reaction

Willadsen

Eggerer

1975

European Journal of Biochemistry

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1. A specimen of stereospecifically 2-tritiated 3-hydroxybutyric acid was prepared by hydroboration of ethyl crotonate. It was assumed that the hydroboration reaction took a syn course and hence that (2R,3S) + (2S,3R)-3-hydro~y[2-~H,]butyric acid was formed after oxidation and hydrolysis.2. 3RS-3-Hydro~y[2-~H,]butyric acid, symmetrically tritiated at C-2, was prepared by isotopic exchange of ethyl acetoacetate in tritiated water, followed by reduction and hydrolysis.3. The 3R-enantiomers of the acids listed under paragraphs (1) and (2) were destroyed enzymically by use of 3R-specific 3-hydroxybutyrate dehydrogenase and the residual 3S-enantiomers were isolated.4. The resulting specimens of 2R,3S-3-hydro~y[2-~H,]butyric acid and 3S-3-hydro~y[2-~H,]-butyric acid were converted chemically to the acyl-CoA derivatives. These were incubated with enoylCoA hydratase. In the presence of the enoyl-CoA hydratase symmetrically labelled 3S-3-hydro~y[2-~H,]butyryl-CoA lost nearly 50 % of its tritium label; 2R,3S-3-hydro~y[2-~H,]butyryl-CoA lost about 78 %.6. It was concluded that the elimination of the elements of water from 3-hydroxybutyryl-CoA on the hydratase occurs stereospecifically with syn geometry.Enoyl-CoA hydratase is responsible for the hydration of 2-enoyl-acyl-CoA esters during the C-3 oxidation of fatty acids. The enzyme isolated from beef liver is relatively non-specific, hydrating, for example, crotonyl-CoA to the 3S-hydroxybutyryl-CoA and isocrotonyl-CoA to the 3R-ester, the latter reaction occurring more slowly [2]. However, the biologically important reaction is the hydration of the trans-enoyl esters to the 3S-product. An investigation of the stereochemistry of the reaction was undertaken not only to gain insight into the chemistry of the enzymic process but also as a means for preparing stereo-A preliminary account of this work has appeared elsewhere [I] but the stereochemical course of the enoyl-CoA hydratase reaction had erroneously been given as anti.Enzymes. Acetyl-CoA acetyltransferase or thiolase (EC 2.3.1.9); carboxylesterase (EC 3.1 . chemically-defined substrates for a second enzyme, acetyl-CoA acetyltransferase. The work with this second enzyme is reported in the accompanying Determination of the direction of the hydratasecatalyzed dehydration requires preparation of a substrate of known or predictable stereochemistry. This was done by hydroboration of ethyl crotonate since the hydroboration reaction has been found to lead to the addition of the elements of water to a double bond with a high degree of stereospecificity. It has been shown in the few cases where A"-unsaturated esters were subjected to hydroboration that reduction of the ester group occurs as the predominant side reaction [4,5]. However, ethyl 3-hydroxypropionate has been prepared in 9 % yield from ethyl acrylate [4].A potential problem in stereochemical experiments with enoyl-CoA hydratase is the presence of contaminating activities, those of 3-cis,2-trans-enoyl-CoA isomerase [6] and 3-hydroxyacyl-CoA 3-epimerase [6,7]. The form...

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confidence: 99%

Substrate Stereochemistry of the Enoyl‐CoA Hydratase Reaction

Willadsen

Eggerer

1975

European Journal of Biochemistry

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“…Hydroboration of unsaturated esters was observed by Brown and Keblys [28]. The authors found that the unusual reactivity of ethyl acrylate, suggesting that the hydroboration-reduction of this ester must proceed at very different rates.…”

Section: Hydroboration Of Unsaturated Estersmentioning

confidence: 93%

Boranes in Organic Chemistry 1. α-Carbonylalkyl- and β-Oxyalkylboranes in Organic Synthesis

Dembitsky

Толстиков

Srebnik

2017

Eurasian Chem. Tech. J.

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This review is devoted to the synthesis of α-carbonylalkyl-and β-hydroxy-alkyl boranes and their use in organic synthesis. α-Carbonyl-alkylboranes include several heteroatomic compounds, in particular, [1.2.3]-diazaborinines, uracyl boronic acids, and [1.2.3.4]diaza-diboretes. The latter type has been obtained by the ketene aminoborations. The reactions of halogenboranes with diazoesters and sulfur ylides resulting in formation of α-carbonyl alkylborates containing diazofunction or ylide structural fragment are described. Amino and halogen boration of acetylenic acid esters was also used for the synthesis of α-carbonyl alkyl boranes. Reactions involving Cr-carbene complexes and acetylenic borone esters were presented for the synthesis of naphthoquinone boronic acids. The formation of amidoboranes by boration of dichloroacetanilides was remined. Boration of 4,8-dimethoxy-2-quinolone with trimethylborates leading to 2-quinolone-3-boronic acid was described. The common synthetic method to α-carbonyl alkyl boranes based on the hydroboration of acrylic acid derivatives was discussed. The results of enhydrazones hydroboration, leading to stable cyclic complexes have been mentioned. The interaction of α-bromoketones with trialkyl or dialkylboranes represents as a general synthetic method to α-carbonyl alkyl boranes. Synthetic approaches to β-hydroxy alkyl boranes are performed. The wide spread hydroboration of vinyl and allyl esters received a well-described attention. The hydroboration of cyclanone enol acetates, 3-keto-and 17-keto-steroids and cyclic allyl alcohol acetates was discussed. The results of aliphatic and alicyclic vinyl esters (including dihydrofuran derivatives) boralylation leading to β-hydroxy alkyl boranes have been envisaged. The synthesis of optically active β-hydroxy alkyl boranes using chiral borane hydrides was discussed. The heterocyclic boran dihydrides are obtained by the hydroboration of dihydropyranes, chromenes and flavenes. Borosilylation of allyl allenylic esters was also been envisaged. The synthetic scheme to optically active boranes and further optically active alcohols were presented. The problems of selectivity regularities in hydroboration reaction by intermolecular complex formations have been discussed.

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“…The effects of heterosubstituents can be overcome through hydroborating agents of specific structure, for instance 3-butenyl derivatives [50], propiolic acid esters [51], propargyl chloride [52], allyl [53], allyl sufonates [54] and also for 2-bromonorbornene [55]. A high degree of selectivity was found for 9-BBN in case of 2-bromo-85 and/or 2-chloronorbornanes 86.…”

Section: Reactions Of Norbornanes With Halidesmentioning

confidence: 99%

“…For example, 1-chloropropene reacted with BSia 2 to form cyclopropane 161 via γ-boryl alkyl chloride 162 [53,84]. The same compound 161 could be obtained using diborane where 163 was as intermediate (Scheme 55) [64,65].…”

Section: Scheme 53mentioning

confidence: 99%

Boranes in Organic Chemistry 3. α-, β- and γ-Haloalkylboranes: The Perspective Vehicles for Organic Synthesis

2016

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<p>The methods of synthesis of α− and β−haloalkylboranes, including chloration of alkylboronic acid esters, additive bromation and chloration of esters of vinyl- and alkenylboronic acids, addition of bromine to trivinylborazines have been considered. The reactions of radical addition of polyhaloidmethanes to vinylboranes, α− and β−unsaturated boronic esters, B-vinyl-B-arylboronic esters, B-trivinyl-B-triarylborazines were discussed. The hydroboration of acetylenic halogenides of dicycloalkylboranes, which led to halocontaining derivatives of dialkylvinylborane was separately considered. The examples of hydroboration of halogenides of allyl and vinyl types are presented. The reaction of dienic synthesis, which takes place between vinylchloroboranes or vinylboronic esters and tetra- or hexachlorocyclopentadienes has been discussed. The reaction of alkenes and allenes with boron tribromide was described. The Markovnikov and non-Markovnikov hydrobromation of boron vinylderivatives has been envisaged. The approaches to the synthesis of perfluoroalkylboranes on the base of hydroboration of perfluoroalkenes have been discussed. The methods of the synthesis of boronates, containing halogetaryl substituents, have been performed. The reactions of hydroboration of halogenides of allylic and propargylic types by 9-borabicyclononane have been shown. The regio- and stereoselectivity of the reaction has been discussed. The examples of the synthesis of boranes of the norbornene type were presented. The reaction of boroallylilation of allyl- and propargylhalogenides leading to the derivatives of 3-bora-bicyclo[3,3,1]-nonane has been discussed. Some directions of using of haloidalkylboranes in the synthesis have been discussed. The examples of nucleophilic substitution leading to oxyalkyl- and azidoalkylboranes have been presented. The route of obtaining of alcohols from α−haloidalkylboranes has been shown. The general scheme of synthesis of α−aminoboronic acids was perfomed. The general approach to the synthesis of allenes on the base of hydroboration products of propargyl halogenides has been discussed. The schemes of synthesis of 1,4-disubstituted-1,2,3-butatrienes are presented. The wide using reaction of introducing of vinylic group into substituent, bonding with boron atom in molecules of dialkylvinylboranes, was discussed. The reactions of new C-C bonds formation, based on the action of iodine on the alkylvinylboronates leading to 1,3-dienes and alkylidencyclanes have been shown. Τhe route of the synthesis of cyclopropanes from β−haloidalkylboranes has been discussed.</p>

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Hydroboration. XXII. The Reaction of Unsaturated Esters with Diborane and Disiamylborane

Cited by 56 publications

References 0 publications

Substrate Stereochemistry of the Enoyl‐CoA Hydratase Reaction

Substrate Stereochemistry of the Enoyl‐CoA Hydratase Reaction

Boranes in Organic Chemistry 1. α-Carbonylalkyl- and β-Oxyalkylboranes in Organic Synthesis

Boranes in Organic Chemistry 3. α-, β- and γ-Haloalkylboranes: The Perspective Vehicles for Organic Synthesis

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