Indução assimétrica 1,5-Anti na adição de enolatos de boro de metilcetonas beta-oxigenadas a aldeídos

Dias, Luiz C.; Aguilar, Andrea M.

doi:10.1590/s0100-40422007000800036

Cited by 13 publications

(4 citation statements)

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“…Thus, it is clear that the major contribution to the sense of 1,5- syn induction observed in aldol reactions involving boron enolates of methylketones 1 − 4 is due to the volume of the substituent at the β-position and not to electronic effects, as stated previously …”

supporting

confidence: 53%

“…Since then, numerous approaches from the research groups of Paterson, Evans, Denmark, Dias, and others have shown that the sense of induction in aldol reactions of boron enolates of β-alkoxy methylketones with aldehydes favors the formation of the 1,5- anti diastereoisomer. However, we demonstrated that it is possible to obtain good levels of 1,5- syn induction from β-trifluoromethyl and β-trichloromethyl-β-alkoxy methylketones independent of the nature of the β-alkoxy protecting group (Scheme ). , …”

mentioning

confidence: 99%

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Influence of β-Substituents in Aldol Reactions of Boron Enolates of β-Alkoxy Methylketones

et al. 2010

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Moderate to good levels of substrate-based 1,5-syn-stereocontrol could be achieved in the boron-mediated aldol reactions of β-tert-butyl methylketones with achiral aldehydes, independent of the nature of the β-alkoxy protecting group (P = PMB or TBS). The analysis of the relative energies of the transition structures by theoretical calculations using the density functional B3LYP shows relative energies favoring the corresponding OUT-1,5-SYN transition structures, explaining the observed 1,5-syn stereoinduction.

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confidence: 53%

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confidence: 99%

Influence of β-Substituents in Aldol Reactions of Boron Enolates of β-Alkoxy Methylketones

et al. 2010

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“…Furthermore, in the asymmetric version of the reaction, new stereogenic carbons can be generated with high levels of selectivity. [4][5][6][7][8] In biological systems, aldol reactions are promoted reversibly and stereoselectively by a group of enzymes known as fructose 1,6bisphosphate aldolases, or simply aldolases. 1,4,[9][10][11] Since its first use in 1971, [12][13][14] the amino acid L-proline has showed itself as an efficient and versatile organocatalyst for aldol reactions.…”

Section: Introductionmentioning

confidence: 99%

Chiral organocatalysts based on lipopeptide micelles for aldol reactions in water

Soares

Aguilar

Silva

et al. 2017

Phys. Chem. Chem. Phys.

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A comprehensive study of the self-assembly in water of a lipopeptide consisting of a sequence of l-proline, l-arginine and l-tryptophan with a hydrocarbon chain has been performed. Fluorescence assays were used to determine the critical aggregation concentration. In situ small-angle X-ray scattering (SAXS) and molecular dynamics simulations showed the presence of spherical micelles with diameters around 6 nm. In agreement with these results, cryo-TEM images showed globular aggregates with diameters ranging from ≈4 nm up to ≈9 nm. Furthermore, the lipopeptide catalytic activity has been tested for the direct aldol reaction between cyclohexanone and p-nitrobenzaldehyde, and we have observed that the self-association of the organocatalyst played a critical role in the enhanced activity. Water affects the selectivity, and poor results are obtained under neat reaction conditions. The location of the catalytic groups at the lipopetide/water solvent interface also endowed unusual selectivity in the catalyzed aldol reactions. Under optimized reaction conditions, high yields (up to >99%), good enantioselectivity (ee up to 85%) and high diastereoselectivity (ds up to 92 : 8) were obtained.

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“…39 Para o entendimento de reações aldólicas de metilcetonas, onde um único centro estereogênico é formado, assim como para compreensão dos fatores envolvidos na estereoindução 1,5 de metilcetonas, recomendam-se os trabalhos de Dias e colaboradores. 40 Aldolatos podem equilibrar suas formas sin e anti por enolização ou por aldolização reversa. Entretanto, na maioria dos casos, o mecanismo para o equilíbrio sin-anti parece envolver a aldolização reversa.…”

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Aldol reactions

Martins¹

2009

Revista Virtual De Química

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Abstract:The aldol reaction is one of the most powerful tools for C-C bond formation in organic synthesis. The C-C bond is formed by a reaction between an enolizable carbonyl compound and a carbonyl compound acting as an electrophile to produce a β-hydroxycarbonyl compound named aldol. One or two stereocenters can be formed with stereochemical control. Since the β-hydroxycarbonyl unit is present in a variety of natural products, the aldol reaction has been used in the synthesis of several biologically important substances. In this work, some important aspects of this useful reaction like regiochemistry, stereochemistry and different methodologies introduced since its discovery will be addressed.Keywords: aldol; C-C bond formation; stereochemistry; regiochemistry; -hydroxycarbonyl compounds ResumoA reação aldólica é uma das ferramentas mais poderosas da síntese orgânica para a construção de ligações C-C. Esta ligação é formada através da reação entre uma substância carbonílica enolizável que age como nucleófilo e outra substância carbonílica que age como eletrófilo. Como resultado da reação, obtém-se um produto β-hidróxi-carbonilado que se denomina aldol. Um ou dois centros estereogênicos podem ser gerados com controle sobre os mesmos. Uma vez que a unidade β-hidróxi-carbonila está presente em vários produtos naturais, a reação aldólica foi empregada em diversas oportunidades na síntese de substâncias de importância biológica. Neste trabalho, são abordados fatores importantes no que concerne à reação aldólica tais como a estereoquímica e a regioquímica, bem como as diferentes metodologias introduzidas desde a sua descoberta.

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Indução assimétrica 1,5-Anti na adição de enolatos de boro de metilcetonas beta-oxigenadas a aldeídos

Cited by 13 publications

References 53 publications

Influence of β-Substituents in Aldol Reactions of Boron Enolates of β-Alkoxy Methylketones

Influence of β-Substituents in Aldol Reactions of Boron Enolates of β-Alkoxy Methylketones

Chiral organocatalysts based on lipopeptide micelles for aldol reactions in water

Aldol reactions

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