Non-stabilized enolates – versatile nucleophiles in transition metal-catalysed allylic alkylations

Kazmaier, Uli

doi:10.1039/c6qo00192k

Cited by 55 publications

(30 citation statements)

References 188 publications

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“…[2d] Palomo reported in 2001 a methodology for the asymmetric construction of α-alkylated ketones (Scheme 2). [15] Although far from a direct method, this strategy accomplished the sequential introduction of three alkyl groups by the use of (1 R )-(+)-camphor.…”

Section: Enolates and Azaenolatesmentioning

confidence: 99%

“…[16] En- ders reported the use of ( S )- and ( R )-1-amino-2-methoxypyr- rolidine dialkyl hydrazines as chiral auxiliaries for the a- alkylation of hydrazones (Scheme 3). Although this methodology has been widely applied to a number of total syntheses, [2d] it harbors some limitations. The formation of the azaenolate requires exposure to lithium diisopropylamide for long periods (because the hydrazones are weakly acidic) and the alkylation must be conducted at very low temperatures (—78 °C to —110°C), making large-scale applications impractical.…”

Section: Enolates and Azaenolatesmentioning

confidence: 99%

“…[2] For example we now have methods for the direct α- alkylation of aldehydes [3] and carboxylic acids. [4] Thus it is perhaps surprising that the general, direct asymmetric alkylation (including allylation) of ketones remains elusive.…”

Section: Introductionmentioning

confidence: 99%

“…Even the most simple asymmetric alkylation reactions involving ketones have not been reported (Figure 1b). [2c,5] …”

Section: Introductionmentioning

confidence: 99%

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Direct Asymmetric Alkylation of Ketones: Still Unconquered

2017

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The alkylation of ketones is taught at basic undergraduate level. In many cases this transformation leads to the formation of a new stereogenic center. However, the apparent simplicity of the transformation is belied by a number of problems. So much so, that a general method for the direct asymmetric alkylation of ketones remains an unmet target. Despite the advancement of organocatalysis and transition-metal catalysis, neither field has provided an adequate solution. Indeed, even use of an efficient and general stoichiometric chiral reagent has yet to be reported. Herein we describe the state-of-the-art in terms of direct alkylation reactions of some carbonyl groups. We outline the limited progress that has been made with ketones, and potential routes towards ultimately achieving a widely applicable methodology for the asymmetric alkylation of ketones.

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Section: Enolates and Azaenolatesmentioning

confidence: 99%

Section: Enolates and Azaenolatesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Even the most simple asymmetric alkylation reactions involving ketones have not been reported (Figure 1b). [2c,5] …”

Section: Introductionmentioning

confidence: 99%

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Direct Asymmetric Alkylation of Ketones: Still Unconquered

2017

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“…[1] Such reactions with enolates derived from ketones and aldehydes form products bearing α-stereogenic centers [2] , β-stereogenic centers [3] , or both [4] . These reactions of stabilized enolates generated from carboxylic acid derivatives containing proximal electron-withdrawing groups (such as acyl, carboxyalkyl, nitro or cyano groups), [5] heteroatom functionalities [6] , or aromatic substituents [7] also occur.…”

mentioning

confidence: 99%

Iridium‐Catalyzed Enantioselective Allylic Substitution of Aliphatic Esters with Silyl Ketene Acetals as the Ester Enolates

Jiang

Hartwig

2017

Angew Chem Int Ed

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Enantioselective allylic substitutions with enolates derived from aliphatic esters under mild conditions remain challenging. Herein we report iridium-catalyzed enantioselective allylations of silyl ketene acetals, the silicon enolates of esters, to form products containing a quaternary carbon at the nucleophile moiety and a tertiary carbon at the electrophile moiety. Under relatively neutral conditions, the allylated aliphatic esters were obtained with excellent regioselectivity and enantioselectivity. These products were readily converted to primary alcohols, carboxylic acids, amides, isocyanates, and carbamates, as well as tetrahydrofuran (THF) and γ-butyrolactone derivatives, without erosion of enantiomeric purity.

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Synergistic Cu/Pd Catalysis for Enantioselective Allylation of Ketimine Esters: The Direct Synthesis of α‐Substituted α‐Amino Acids and 2H‐Pyrrols

2018

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An efficient synergistic Cu/Pd catalyzed enantioselective a-allylation of acyclic ketimine esters has been reported, which provides an entry to nonproteinogenic a-allyl a-amino acids in high yield, exclusive regioselectivity, and excellent enantioselectivity. Moreover, the more challenging cyclic ketimine ester could also be employed as a nucleophile for the construction of 3,4-dihydro-2Hpyrrole derivatives bearing a quaternary stereogenic center using the same catalytic system.

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Non-stabilized enolates – versatile nucleophiles in transition metal-catalysed allylic alkylations

Abstract: This review covers new developments in the transition metal-catalyzed allylic alkylations of non-stabilized enolates, preferentially generated from ketone, esters or amides.

Cited by 55 publications

References 188 publications

Direct Asymmetric Alkylation of Ketones: Still Unconquered

Direct Asymmetric Alkylation of Ketones: Still Unconquered

Iridium‐Catalyzed Enantioselective Allylic Substitution of Aliphatic Esters with Silyl Ketene Acetals as the Ester Enolates

Synergistic Cu/Pd Catalysis for Enantioselective Allylation of Ketimine Esters: The Direct Synthesis of α‐Substituted α‐Amino Acids and 2H‐Pyrrols

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