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Enantioselective and Enantiospecific Transition-Metal-Catalyzed Cross-Coupling Reactions of Organometallic Reagents To Construct C-C Bonds.

Cherney AH, Kadunce NT, Reisman SE - Chem. Rev. (2015)

View Article: PubMed Central - PubMed

Affiliation: The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.

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reagents in asymmetric alkyl cross-coupling reactions, with Hayashi, a single example of an asymmetric cross-coupling between sec-alkyl organic halides and organosilicon reagents has been reported stereoconvergent cross-coupling reactions between sec-alkyl electrophiles and either C(sp)- or C(sp)-hybridized organometallic reagents, Sestelo, Sarandeses, (Scheme 9a)... This result and π-allylmetal complex... Unselective reductive selectivity for the (Z)-alkene in most cases; MeMgBr resulted in decreased regioselectivity... increasing the C1–C1′ separation and disfavoring 1,1′ reductive elimination... use in asymmetric allylic alkylation reactions: any successful transformations the allenylmetal and its isomeric propargylmetal species prior to reductive elimination... the analogous asymmetric cross-coupling reactions of tert-alkyl partners represent a largely undeveloped area of great synthetic

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α-Selective stereospecific allylic substitutions with organomagnesiumreagents.
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fig83: α-Selective stereospecific allylic substitutions with organomagnesiumreagents.

Mentions: Several groups have investigated Cu-catalyzed stereospecific α-selective allylic substitution reactions. In 2010,Bäckvall and co-workers reported their investigations of theCuI-catalyzed coupling of enantioenriched cinnamaldehyde-derivedester 416 with alkyl and aryl Grignard reagents to givestyrenyl products 417 and 418 with inversionof stereochemistry (Figure 83a). High levels of α-selectivity and excellent es werereported for a range of nucleophiles, although alkyl Grignard reagentsreacted with somewhat lower levels of regioselectivity.320−322 Bäckvall rationalized that the α:γ-selectivityof the transformation is determined by the relative rates of reductiveelimination (k1) versus π-allylformation (k2, k2′) (Figure 83, b). If k1 > k2, then γ-alkylated product 421 isobtained; however, if the rate of reductive elimination is slow, formationof π-allyl 422 can give rise to the thermodynamicallystable α-product, 423. The intermediacy of an electron-richcuprate is expected to slow reductive elimination further, favoringdelivery of the α-product. The authors ascribe the erosion ofenantiospecificity in some substrates to π-allyl formation viaconformation 424, giving rise to undesired 426.


Enantioselective and Enantiospecific Transition-Metal-Catalyzed Cross-Coupling Reactions of Organometallic Reagents To Construct C-C Bonds.

Cherney AH, Kadunce NT, Reisman SE - Chem. Rev. (2015)

α-Selective stereospecific allylic substitutions with organomagnesiumreagents.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4566132&req=5

fig83: α-Selective stereospecific allylic substitutions with organomagnesiumreagents.
Mentions: Several groups have investigated Cu-catalyzed stereospecific α-selective allylic substitution reactions. In 2010,Bäckvall and co-workers reported their investigations of theCuI-catalyzed coupling of enantioenriched cinnamaldehyde-derivedester 416 with alkyl and aryl Grignard reagents to givestyrenyl products 417 and 418 with inversionof stereochemistry (Figure 83a). High levels of α-selectivity and excellent es werereported for a range of nucleophiles, although alkyl Grignard reagentsreacted with somewhat lower levels of regioselectivity.320−322 Bäckvall rationalized that the α:γ-selectivityof the transformation is determined by the relative rates of reductiveelimination (k1) versus π-allylformation (k2, k2′) (Figure 83, b). If k1 > k2, then γ-alkylated product 421 isobtained; however, if the rate of reductive elimination is slow, formationof π-allyl 422 can give rise to the thermodynamicallystable α-product, 423. The intermediacy of an electron-richcuprate is expected to slow reductive elimination further, favoringdelivery of the α-product. The authors ascribe the erosion ofenantiospecificity in some substrates to π-allyl formation viaconformation 424, giving rise to undesired 426.

View Article: PubMed Central - PubMed

Affiliation: The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.

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Please rate it.

reagents in asymmetric alkyl cross-coupling reactions, with Hayashi, a single example of an asymmetric cross-coupling between sec-alkyl organic halides and organosilicon reagents has been reported stereoconvergent cross-coupling reactions between sec-alkyl electrophiles and either C(sp)- or C(sp)-hybridized organometallic reagents, Sestelo, Sarandeses, (Scheme 9a)... This result and π-allylmetal complex... Unselective reductive selectivity for the (Z)-alkene in most cases; MeMgBr resulted in decreased regioselectivity... increasing the C1–C1′ separation and disfavoring 1,1′ reductive elimination... use in asymmetric allylic alkylation reactions: any successful transformations the allenylmetal and its isomeric propargylmetal species prior to reductive elimination... the analogous asymmetric cross-coupling reactions of tert-alkyl partners represent a largely undeveloped area of great synthetic

No MeSH data available.