Asymmetric Synthesis of a Quaternary Carbon Stereogenic Center by Organocatalysis Using a Primary Amino Acid and Its Salt

Yoshida, Masanori

doi:10.1002/tcr.202200276

Cited by 3 publications

(2 citation statements)

References 126 publications

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“…Next, the addition of an inorganic base was tested (Table ). A base can be expected to trap acids and tune the transition state by changing the CO 2 H to CO 2 M (M = metal) in the catalyst. − …”

Section: Resultsmentioning

confidence: 99%

Alkali Carbonates Improve β,β-Diaryl Serine-Catalyzed Enantioselective α-Fluorination of β-Dicarbonyl Compounds

Endo,

Tomon,

Arimitsu

2023

J. Org. Chem.

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Herein, we report the highly enantioselective α-fluorination of both cyclic and acyclic β-dicarbonyl compounds, including β-diketones, β-ketoesters, and β-ketoamides. The reactions with β,β-diaryl serines as primary amine organocatalysts were enhanced by adding alkali carbonates, such as Na2CO3 or Li2CO3, and enabled the reaction to be conducted with only 1.1 equiv of Selectfluor. The optimal conditions afforded the α-fluorinated β-dicarbonyl compounds in 50–99% yield with excellent enantioselectivity (up to 98% ee).

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Section: Resultsmentioning

confidence: 99%

Alkali Carbonates Improve β,β-Diaryl Serine-Catalyzed Enantioselective α-Fluorination of β-Dicarbonyl Compounds

Endo,

Tomon,

Arimitsu

2023

J. Org. Chem.

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“…Assuming that the added acid will react immediately with the α-amino acid basic salt to produce the free α-amino acid, authors hypothesized that the actual catalytic system would consist of a mixture of free and deprotonated forms of the α-amino acid. Further refinement allowed to determine that a 4:1 mixture of free and lithium salt forms is the optimum for the reaction ( Scheme 34 b) [ 129 , 130 ]. Under these conditions, the corresponding α-quaternary aldehydes 84 were obtained in good yields and usually high diastereo- and enantioselectivity.…”

Section: Methods Based On Combined Use Of α-Amino Acid Catalysts and ...mentioning

confidence: 99%

Catalytic Asymmetric α-Functionalization of α-Branched Aldehydes

et al. 2023

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Aldehydes constitute a main class of organic compounds widely applied in synthesis. As such, catalyst-controlled enantioselective α-functionalization of aldehydes has attracted great interest over the years. In this context, α-branched aldehydes are especially challenging substrates because of reactivity and selectivity issues. Firstly, the transient trisubstituted enamines and enolates resulting upon treatment with an aminocatalyst or a base, respectively, would exhibit attenuated reactivity; secondly, mixtures of E- and Z-configured enamines/enolates may be formed; and third, effective face-discrimination on such trisubstituted sp2 carbon intermediates by the incoming electrophilic reagent is not trivial. Despite these issues, in the last 15 years, several catalytic approaches for the α-functionalization of prostereogenic α-branched aldehydes that proceed in useful yields and diastereo- and enantioselectivity have been uncovered. Developments include both organocatalytic and metal-catalyzed approaches as well as dual catalysis strategies for forging new carbon–carbon and carbon–heteroatom (C-O, N, S, F, Cl, Br, …) bond formation at Cα of the starting aldehyde. In this review, some key early contributions to the field are presented, but focus is on the most recent methods, mainly covering the literature from year 2014 onward.

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Effect of the regulation of quinine in Cinchona Base derived primary amine on the addition reaction of nitrostyrene with 2-methylpropionaldehyde

Haiyang

2024

Preprint

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The Michael addition of nitrostyrene and 2-methylpropionaldehyde catalyzed via cinchona alkaloid-based primary amines (9-epi-QDA-R'') with the aid of benzoic acid have been carried out at the PCM(toluene)/B3LYP/6-311 + + G(2df,2p)//B3LYP/6-31G(d) level. The calculations showed that the whole reaction consisted of four consecutive steps: ⑴ the production of an imine ion intermediate, ⑵ an addition reaction between the imine ion and nitrostyrene, ⑶ the second proton transfer stage, and ⑷ hydrolysis and regeneration stage of the catalyst. The rate-determining step of the whole reaction is the addition process between the imine ion and nitrostyrene. The correlation calculations determined that 9-epi-QDA-R'' containing -NH electron-absorbing group in the quinine ring exhibit stronger activation than that containing -CH2 electron-donating group, while 9-epi-QDA-R'' with -NCONHPh electron-absorbing group in the quinine ring exhibit weaker activation than that containing -CH2 electron-donating group. Natural Bond Orbital analysis of atomic charges of the tertiary amine nitrogen in the quinine ring determined that the electron-absorbing group slightly reduce the negative charges on the nitrogen atom of the tertiary amine, which is favorable for the addition reaction of the imine ion to nitrostyrene. However, the negative charge on tertiary amine nitrogen is much reduced by the electron-absorbing substituents, which is not conducive to the addition reaction of nitrostyrene with the imine ion. Accordingly, the calculations exhibit that the charge distribution of the nitrogen atom of the tertiary amine influences the catalytic efficiency of the whole system.

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Asymmetric Synthesis of a Quaternary Carbon Stereogenic Center by Organocatalysis Using a Primary Amino Acid and Its Salt

Cited by 3 publications

References 126 publications

Alkali Carbonates Improve β,β-Diaryl Serine-Catalyzed Enantioselective α-Fluorination of β-Dicarbonyl Compounds

Alkali Carbonates Improve β,β-Diaryl Serine-Catalyzed Enantioselective α-Fluorination of β-Dicarbonyl Compounds

Catalytic Asymmetric α-Functionalization of α-Branched Aldehydes

Effect of the regulation of quinine in Cinchona Base derived primary amine on the addition reaction of nitrostyrene with 2-methylpropionaldehyde

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