Construction of chiral α-<i>tert</i>-amine scaffolds <i>via</i> amine-catalyzed asymmetric Mannich reactions of alkyl-substituted ketimines

Homma, Chihiro; Takeshima, Aika; Kano, Taichi; Maruoka, Keiji

doi:10.1039/d0sc05269h

Cited by 14 publications

(6 citation statements)

References 111 publications

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“…Nonetheless, N-Boc alkynyl alkyl ketimines are hardly accessible in a single diastereomeric form through dehydrative condensation reaction. Therefore, they developed the synthesis of N-Boc-protected alkynyl alkyl ketimines ((1) and (2), Scheme 26) and then proceeded to evaluate them for chiral amine-catalyzed Mannich reactions (3) [97]. (Z)-Alkynyl alkyl ketimines underwent chiral amine-catalyzed Mannich reaction smoothly with aldehyde nucleophiles.…”

Section: Direct Mannichmentioning

confidence: 99%

Asymmetric Catalytic Ketimine Mannich Reactions and Related Transformations

Reep

Jarvis

et al. 2021

Catalysts

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The catalytic enantioselective ketimine Mannich and its related reactions provide direct access to chiral building blocks bearing an α-tertiary amine stereogenic center, a ubiquitous structural motif in nature. Although ketimines are often viewed as challenging electrophiles, various approaches/strategies to circumvent or overcome the adverse properties of ketimines have been developed for these transformations. This review showcases the selected examples that highlight the benefits and utilities of various ketimines and remaining challenges associated with them in the context of Mannich, allylation, and aza-Morita–Baylis–Hillman reactions as well as their variants.

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Section: Direct Mannichmentioning

confidence: 99%

Asymmetric Catalytic Ketimine Mannich Reactions and Related Transformations

Reep

Jarvis

et al. 2021

Catalysts

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“…In addition, optically active lactone 9 was obtained from 4 a via a four-step sequence: Pinnick oxidation, methyl esterification, reduction with NaBH 4 , and subsequent cyclization with p-TsOH. [15] To gain preliminary mechanistic insight into the present cross-coupling reaction, several control experiments were performed. Replacement of bromine atoms of substrates with chlorine atoms resulted in lower yield or no reaction (Scheme 6a and 6b).…”

Section: Methodsmentioning

confidence: 99%

Diethylzinc‐Mediated Cross‐Coupling Reactions between Dibromoketones and Monobromo Carbonyl Compounds

Takeshima

Kano

2023

Angew Chem Int Ed

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A novel route to synthesize 1,4-dicarbonyl compounds is described. α,α-Dibromoketones generate zinc enolates through a diethylzinc-mediated halogenmetal exchange and react with α-bromocarbonyl compounds to furnish 1,4-dicarbonyl compounds via a second generation of zinc enolates. This cross-coupling reaction is enabled by the chemoselective formation of zinc enolates from α,α-dibromoketones in the presence of α-bromocarbonyl compounds. Chiral 1,4-dicarbonyl compounds can be obtained via the enantioselective bromination of aldehydes using a chiral secondary amine catalyst and a subsequent cross-coupling reaction between the resulting chiral α-bromoaldehydes and α,αdibromoacetophenones.

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“…We describe herein the results of a catalytic asymmetric Mannich reaction using alkyl alkynyl ketimines and an asymmetric conjugate addition to alkenyl alkynyl ketimines. [24][25][26] To the best of our knowledge, amine-catalyzed asymmetric reactions using ketimines that bear both alkyl and alkenyl groups or two alkyl groups on the imine carbon have not been reported. 27 The development of asymmetric reactions with ketimines has been hampered by the presence of stereoisomers of ketimines and their lower reactivity compared to that of aldimines.…”

Section: Cluster Account Synlettmentioning

confidence: 99%

“…We describe herein the results of a catalytic asymmetric Mannich reaction using alkyl alkynyl ketimines and an asymmetric conjugate addition to alkenyl alkynyl ketimines. 24 25 26…”

Section: Development Of Asymmetric Reactions Catalyzed By a Novel Chi...mentioning

confidence: 99%

The Design and Synthesis of Phenylcyclopropane-Based Secondary Amine Catalysts and Their Applications in Asymmetric Reactions

Takeshima

Kano

2022

Synlett

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Most chiral secondary amine catalysts are usually synthesized from chiral amino acids and their derivatives. On the other hand, the amine catalysts based on a binaphthyl backbone have previously been developed, and show unique chemo- and stereoselectivity in some asymmetric reactions. In spite of their utility, however, the applications of binaphthyl-based amines in asymmetric reactions are still rare due to their synthetic inefficiency. In this context, we designed amine catalysts possessing a phenylcyclopropane scaffold as a novel chiral motif. The novel catalysts could be synthesized easily and construct a similar chiral environment to that of binaphthyl-based amine catalysts. In addition, the phenylcyclopropane-based amino sulfonamide was found to be an effective catalyst for the syn-selective Mannich reaction and conjugate addition using alkynyl Z-ketimines.

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Construction of chiral α-tert-amine scaffolds via amine-catalyzed asymmetric Mannich reactions of alkyl-substituted ketimines

Abstract: Stereoselective Mannich reactions of aldehydes with ketimines provide chiral β-amino aldehydes that bear an α-tert-amine moiety. However, the structural variation of the ketimines is limited due to the formation of...

Cited by 14 publications

References 111 publications

Asymmetric Catalytic Ketimine Mannich Reactions and Related Transformations

Asymmetric Catalytic Ketimine Mannich Reactions and Related Transformations

Diethylzinc‐Mediated Cross‐Coupling Reactions between Dibromoketones and Monobromo Carbonyl Compounds

The Design and Synthesis of Phenylcyclopropane-Based Secondary Amine Catalysts and Their Applications in Asymmetric Reactions

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