6 research outputs found

    Enantioselective Synthesis of Di- and Tri-Arylated All-Carbon Quaternary Stereocenters via Copper-Catalyzed Allylic Arylations with Organolithium Compounds

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    The highly enantioselective copper­(I)/N-heterocyclic carbene (NHC) catalyzed synthesis of di- and triarylated all-carbon quaternary stereocenters via asymmetric allylic arylation (AAAr) with aryl organolithium compounds is demonstrated. The use of readily available or easily accessible aryl organolithium reagents in combination with trisubstituted allyl bromides, in the presence of a copper/NHC catalyst, affords important di- and triarylated all-carbon quaternary stereocenters in good yields and enantioselectivities. This method tolerates a wide range of alkyl and substituted aryl groups in the starting allyl bromides, including less common biaryl moieties, which, in combination with diverse organolithium reagents, delivers a broad scope of products in an operationally straightforward and efficient manner

    Desymmetrization of <i>meso</i>-Dibromocycloalkenes through Copper(I)-Catalyzed Asymmetric Allylic Substitution with Organolithium Reagents

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    The highly regio- and enantioselective (up to >99:1 dr, up to 99:1 er) desymmetrization of <i>meso</i>-1,4-dibromocycloalk-2-enes using asymmetric allylic substitution with organolithium reagents to afford enantioenriched bromocycloalkenes (ring size of 5 to 7) has been achieved. The cycloheptene products undergo an unusual ring contraction. The synthetic versatility of this Cu­(I)-catalyzed reaction is demonstrated by the concise stereocontrolled preparation of cyclic amino alcohols, which are privileged chiral structures in natural products and pharmaceuticals and widely used in synthesis and catalysis

    Desymmetrization of <i>meso</i>-Dibromocycloalkenes through Copper(I)-Catalyzed Asymmetric Allylic Substitution with Organolithium Reagents

    No full text
    The highly regio- and enantioselective (up to >99:1 dr, up to 99:1 er) desymmetrization of <i>meso</i>-1,4-dibromocycloalk-2-enes using asymmetric allylic substitution with organolithium reagents to afford enantioenriched bromocycloalkenes (ring size of 5 to 7) has been achieved. The cycloheptene products undergo an unusual ring contraction. The synthetic versatility of this Cu­(I)-catalyzed reaction is demonstrated by the concise stereocontrolled preparation of cyclic amino alcohols, which are privileged chiral structures in natural products and pharmaceuticals and widely used in synthesis and catalysis

    Desymmetrization of <i>meso</i>-Dibromocycloalkenes through Copper(I)-Catalyzed Asymmetric Allylic Substitution with Organolithium Reagents

    No full text
    The highly regio- and enantioselective (up to >99:1 dr, up to 99:1 er) desymmetrization of <i>meso</i>-1,4-dibromocycloalk-2-enes using asymmetric allylic substitution with organolithium reagents to afford enantioenriched bromocycloalkenes (ring size of 5 to 7) has been achieved. The cycloheptene products undergo an unusual ring contraction. The synthetic versatility of this Cu­(I)-catalyzed reaction is demonstrated by the concise stereocontrolled preparation of cyclic amino alcohols, which are privileged chiral structures in natural products and pharmaceuticals and widely used in synthesis and catalysis

    Stereospecific Ring Contraction of Bromocycloheptenes through Dyotropic Rearrangements via Nonclassical Carbocation‚ÄďAnion Pairs

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    Experimental and theoretical evidence is reported for a rare type I dyotropic rearrangement involving a [1,2]-alkene shift, leading to the regio- and stereo¬≠specific ring contraction of bromo¬≠cyclo¬≠heptenes. This reaction occurs under mild conditions, with or without a Lewis acid catalyst. DFT calculations show that the reaction proceeds through a nonclassical carbocation‚Äďanion pair, which is crucial for the low activation barrier and enantio¬≠specificity. The <i>chiral</i> cyclo¬≠propyl¬≠carbinyl cation may be a transition state or an intermediate, depending on the reaction conditions

    Stereospecific Ring Contraction of Bromocycloheptenes through Dyotropic Rearrangements via Nonclassical Carbocation‚ÄďAnion Pairs

    No full text
    Experimental and theoretical evidence is reported for a rare type I dyotropic rearrangement involving a [1,2]-alkene shift, leading to the regio- and stereo¬≠specific ring contraction of bromo¬≠cyclo¬≠heptenes. This reaction occurs under mild conditions, with or without a Lewis acid catalyst. DFT calculations show that the reaction proceeds through a nonclassical carbocation‚Äďanion pair, which is crucial for the low activation barrier and enantio¬≠specificity. The <i>chiral</i> cyclo¬≠propyl¬≠carbinyl cation may be a transition state or an intermediate, depending on the reaction conditions
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