.alpha.-Halovinylboranes.  Theiir preparation and conversion into.alpha.-Halovinylboranes.  Their preparation and conversion into cis-vinyl halides, trans-olefins, ketones, and transvinylboranes

Zweifel, George; Arzoumanian, Henri

doi:10.1021/ja00995a075

Cited by 130 publications

(30 citation statements)

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“…The excellent regioselectivity in this step may come from the relatively small steric hindrance of the halogen atom compared with the carbon chain or aromatic ring. 13 Then, IA underwent carbopalladation with allylic halides to afford alkyl palladium intermediate IIA, followed by the b-heteroatom elimination to furnish the cishaloallylation product (E)-3 and to regenerate the palladium catalyst (path A, Scheme 2).…”

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confidence: 99%

Palladium-catalyzed highly regio- and stereoselective synthesis of (1E)- or (1Z)-1,2-dihalo-1,4-dienes via haloallylation of alkynyl halides

et al. 2011

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A highly efficient and selective synthesis of (1E)- or (1Z)-1,2-dihalo-1,4-dienes via Pd-catalyzed coupling of haloalkynes and allylic halides is described. The (1E)-1,2-dihalo-1,4-dienes were generated in good yields with excellent stereoselectivities (1E/1Z up to >98/2), while (1Z)-1,2-dihalo-1,4-dienes were produced in excellent yields and stereoselectivities (1Z/1E up to >98/2) by simply adding stoichiometric lithium halides.

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confidence: 99%

Palladium-catalyzed highly regio- and stereoselective synthesis of (1E)- or (1Z)-1,2-dihalo-1,4-dienes via haloallylation of alkynyl halides

et al. 2011

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“…Our interests date back to the synthesis of stereodefined vinylzinc reagents and their additions to aldehydes and ketones to prepare allylic alcohols. , Inspiration for the preparation of ( Z )-vinylzinc intermediates originated from Zweifel, who discovered that 1-halo-1-alkynes undergo highly regioselective hydroborations with dicyclohexylborane (Scheme ). 1-Halo-1-alkenylboranes formed in this way were subjected to addition of nucleophiles, such as sodium methoxide, alkyllithiums, Grignards, and hydrides .…”

Section: Additions Of (Z)-vinylzinc Reagents To Chiral Aldehydesmentioning

confidence: 99%

Chelation-Controlled Additions to Chiral α- and β-Silyloxy, α-Halo, and β-Vinyl Carbonyl Compounds

Fan

Walsh

2017

Acc. Chem. Res.

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The science and art of preventing and managing disease and prolonging life is dependent on advances in medicine, biology, and biochemistry. Many of these advances will involve interactions of small molecules with biological entities. As such, they will rely on the efficient synthesis of active compounds with very high stereochemical purity. Although enantioselective reactions are important in this regard, most stereocenters in complex molecule synthesis are installed in diastereoselective reactions. Perhaps the most well-known diastereoselective C-C bond-forming reaction is the addition of nucleophiles to carbonyl groups with α- or β-stereogenic centers. Diastereoselective additions of organometallic reagents to protected chiral α- and β-hydroxy aldehydes and ketones are described by either Cram chelation or Felkin-Anh models, which are protecting group (PG)-dependent. Small PGs (X = OMOM, OBn, etc.) favor Cram chelation, wherein both the carbonyl group and the O-PG bind to the Lewis acidic metal, providing syn diol motifs. In contrast, silyl PGs, with the OSiR moiety being both bulky and weakly coordinating, provide anti diols (Felkin addition). It is well-known that exceptions to this paradigm are scarce. Therefore, the choice of PG is based on the desired stereochemical outcome in the addition step and is often inappropriate for the global protection strategy. Thus, it is critical to develop general methods for chelation-controlled additions of organometallics to chiral silyloxy aldehydes and ketones. Once the challenge of developing chelation-controlled additions to silyloxy carbonyl compounds can be met, the next question is what other pendant functional groups can chelate? Herein we introduce the first general methods for the chelation-controlled addition of organometallics to chiral silyloxy aldehydes and ketones. A wide variety of organozinc reagents have been used in these addition reactions, including dialkylzinc reagents that are commercially available or generated using Knochel's methods. Existing protocols for the generation of (E)-di- and -trisubstituted vinylzinc reagents have been employed, and new methods for the generation of (Z)-di- and -trisubstituted vinylzinc reagents have been developed. The generation of 1,1-heterobimetallic reagents based on boron and zinc has been advanced, and the addition of these reagents to silyloxy aldehydes via chelation-control is included. We will first describe the initial discovery and a model to explain the observed diastereoselectivities. A wide array of chelation-controlled additions to chiral α- and β-silyloxy aldehydes and ketones will then be presented. We next describe other functional groups that undergo chelation-controlled additions. α-Halo aldehyde derivatives are well-known to favor Felkin addition (via the Cornforth-Evans model). We introduce a general method for chelation-controlled additions to α-halo aldimines that provides useful precursors to aziridines. Finally, we provide preliminary evidence that even C═C bonds can play the role of chelatin...

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“…Thus, the hydroboration of substituted propargyl chlorides provides the convenient route for terminal allenes were β-haloalkyl boranes 55, are the postulated intermediates, in yields of 64-73% (Scheme 16) [29]. Hydroboration of functional alkynes is also possible, and when the functionality is close to the triple bond, further reaction of the boranes may lead to useful synthetic procedure, [30][31][32] where intermediate 56 is β-chloroalkylborane. β-Heterosubstituted alkylboranes can induce β-elimination 57 to form allenes 58 and 59 [33].…”

Section: Hydroboration Of Acetylenesmentioning

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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.alpha.-Halovinylboranes. Theiir preparation and conversion into.alpha.-Halovinylboranes. Their preparation and conversion into cis-vinyl halides, trans-olefins, ketones, and transvinylboranes

Cited by 130 publications

References 1 publication

Palladium-catalyzed highly regio- and stereoselective synthesis of (1E)- or (1Z)-1,2-dihalo-1,4-dienes via haloallylation of alkynyl halides

Palladium-catalyzed highly regio- and stereoselective synthesis of (1E)- or (1Z)-1,2-dihalo-1,4-dienes via haloallylation of alkynyl halides

Chelation-Controlled Additions to Chiral α- and β-Silyloxy, α-Halo, and β-Vinyl Carbonyl Compounds

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

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