DFT investigation of the diastereoselectivity of MX2 and MX3 Lewis acid catalyzed Mukaiyama aldol reaction between C,O,O-tris(trimethylsilyl)ketene acetal and aldehydes

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Abstract

The kinetics and diastereoselectivity of the Mukaiyama aldol reaction between C,O,O-tris(trimethylsilyl)ketene acetal and aldehydes bearing alkyl, vinyl, and aromatic substituents is influenced by the nature of Lewis acid catalysts. A density functional theory investigation using the M06-2X exchange-correlation functional and the PCM scheme to account for solvent effects has been carried out to characterize the structure and energetics of the transition state when the Lewis acid is ZnBr2 (MX2) or GaCl3 (MX3) in comparison to the uncatalyzed reaction. The main observations are that (i) the pro-syn transition states are always more stable than the pro-anti ones; (ii) for MX2, the transition state presents a cyclic structure, whereas it is open for MX3, owing to steric interactions; (iii) the difference of activation free enthalpy between the pro-anti and pro-syn transition states decreases when the reaction is catalyzed, by either MX2 or MX3, demonstrating a reduction of the diastereoselectivity with respect to the uncatalyzed reaction; (iv) this decrease of diastereoselectivity is larger for MX3- than for MX2-catalyzed reactions; and (v) the MX3-catalyzed reactions are kinetically favored by 1-2 kcal mol-1 with respect to the MX2 ones.
Original languageEnglish
Pages (from-to)1938-1947
Number of pages10
JournalJournal of physical chemistry A
Volume122
Issue number8
DOIs
Publication statusPublished - 2018

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acetals
Lewis Acids
Acetals
aldehydes
Aldehydes
Discrete Fourier transforms
Bearings (structural)
acids
Pulse code modulation
Density functional theory
Enthalpy
Chemical activation
Catalysts
Kinetics
3-hydroxybutanal
ketene
enthalpy
activation
density functional theory
catalysts

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@article{3448129d516d441aa4eb06e6da107eb6,
title = "DFT investigation of the diastereoselectivity of MX2 and MX3 Lewis acid catalyzed Mukaiyama aldol reaction between C,O,O-tris(trimethylsilyl)ketene acetal and aldehydes",
abstract = "The kinetics and diastereoselectivity of the Mukaiyama aldol reaction between C,O,O-tris(trimethylsilyl)ketene acetal and aldehydes bearing alkyl, vinyl, and aromatic substituents is influenced by the nature of Lewis acid catalysts. A density functional theory investigation using the M06-2X exchange-correlation functional and the PCM scheme to account for solvent effects has been carried out to characterize the structure and energetics of the transition state when the Lewis acid is ZnBr2 (MX2) or GaCl3 (MX3) in comparison to the uncatalyzed reaction. The main observations are that (i) the pro-syn transition states are always more stable than the pro-anti ones; (ii) for MX2, the transition state presents a cyclic structure, whereas it is open for MX3, owing to steric interactions; (iii) the difference of activation free enthalpy between the pro-anti and pro-syn transition states decreases when the reaction is catalyzed, by either MX2 or MX3, demonstrating a reduction of the diastereoselectivity with respect to the uncatalyzed reaction; (iv) this decrease of diastereoselectivity is larger for MX3- than for MX2-catalyzed reactions; and (v) the MX3-catalyzed reactions are kinetically favored by 1-2 kcal mol-1 with respect to the MX2 ones.",
author = "Beno{\^i}t Champagne and Slim, {Hadj Mohamed} and Mahmoud Trabelsi",
year = "2018",
doi = "10.1021/acs.jpca.7b11186",
language = "English",
volume = "122",
pages = "1938--1947",
journal = "The journal of physical chemistry. A",
issn = "1089-5639",
publisher = "American Chemical Society",
number = "8",

}

TY - JOUR

T1 - DFT investigation of the diastereoselectivity of MX2 and MX3 Lewis acid catalyzed Mukaiyama aldol reaction between C,O,O-tris(trimethylsilyl)ketene acetal and aldehydes

AU - Champagne, Benoît

AU - Slim, Hadj Mohamed

AU - Trabelsi, Mahmoud

PY - 2018

Y1 - 2018

N2 - The kinetics and diastereoselectivity of the Mukaiyama aldol reaction between C,O,O-tris(trimethylsilyl)ketene acetal and aldehydes bearing alkyl, vinyl, and aromatic substituents is influenced by the nature of Lewis acid catalysts. A density functional theory investigation using the M06-2X exchange-correlation functional and the PCM scheme to account for solvent effects has been carried out to characterize the structure and energetics of the transition state when the Lewis acid is ZnBr2 (MX2) or GaCl3 (MX3) in comparison to the uncatalyzed reaction. The main observations are that (i) the pro-syn transition states are always more stable than the pro-anti ones; (ii) for MX2, the transition state presents a cyclic structure, whereas it is open for MX3, owing to steric interactions; (iii) the difference of activation free enthalpy between the pro-anti and pro-syn transition states decreases when the reaction is catalyzed, by either MX2 or MX3, demonstrating a reduction of the diastereoselectivity with respect to the uncatalyzed reaction; (iv) this decrease of diastereoselectivity is larger for MX3- than for MX2-catalyzed reactions; and (v) the MX3-catalyzed reactions are kinetically favored by 1-2 kcal mol-1 with respect to the MX2 ones.

AB - The kinetics and diastereoselectivity of the Mukaiyama aldol reaction between C,O,O-tris(trimethylsilyl)ketene acetal and aldehydes bearing alkyl, vinyl, and aromatic substituents is influenced by the nature of Lewis acid catalysts. A density functional theory investigation using the M06-2X exchange-correlation functional and the PCM scheme to account for solvent effects has been carried out to characterize the structure and energetics of the transition state when the Lewis acid is ZnBr2 (MX2) or GaCl3 (MX3) in comparison to the uncatalyzed reaction. The main observations are that (i) the pro-syn transition states are always more stable than the pro-anti ones; (ii) for MX2, the transition state presents a cyclic structure, whereas it is open for MX3, owing to steric interactions; (iii) the difference of activation free enthalpy between the pro-anti and pro-syn transition states decreases when the reaction is catalyzed, by either MX2 or MX3, demonstrating a reduction of the diastereoselectivity with respect to the uncatalyzed reaction; (iv) this decrease of diastereoselectivity is larger for MX3- than for MX2-catalyzed reactions; and (v) the MX3-catalyzed reactions are kinetically favored by 1-2 kcal mol-1 with respect to the MX2 ones.

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