Assigning the stereochemistry of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters using GIAO 1H NMR chemical shift calculations

Slim Hadj Mohamed; Mahmoud Trabelsi; Benoît Champagne

doi:10.1016/j.molstruc.2017.03.112

Assigning the stereochemistry of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters using GIAO ¹H NMR chemical shift calculations

Slim Hadj Mohamed, Mahmoud Trabelsi, Benoît Champagne

Unit of theoretical and structural physico-chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

The stereostructure of β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters synthesized by Bellassoued et al. [J. Org. Chem. 2001, 66, 5054–5057] using Mukaiyama aldol reaction has been reassigned using density functional theory NMR ¹H chemical shifts calculations. It is now concluded that the major diastereoisomer is syn and the minor is anti. Within this assignment, for all silyl esters, δ_Ha(anti) > δ_Ha(syn), δ_Hb(anti) < δ_Hb(syn), and ³J_Ha-Hb (anti) > ³J_Ha-Hb (syn). Since the experimental assignment was based on the stereostructure (E/Z) of the cinnamic acid obtained by elimination of trimethylsilyl 3-phenyl-3-(trimethylsiloxy)-2-(trimethylsilyl)propanoate in the presence of TiCl₄ and on the assumption that this elimination is anti stereospecific in acidic medium, one arrives at the conclusion that the elimination of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters is not anti stereospecific.

Original language	English
Pages (from-to)	436-440
Number of pages	5
Journal	Journal of molecular structure
Volume	1141
DOIs	https://doi.org/10.1016/j.molstruc.2017.03.112
Publication status	Published - 5 Aug 2017

Keywords

H NMR reassignment
Diastereoselectivity
Mukaiyama aldol reaction

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10.1016/j.molstruc.2017.03.112

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@article{9ba4c11176974b8bbbd4f57505386559,

title = "Assigning the stereochemistry of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters using GIAO 1H NMR chemical shift calculations",

abstract = "The stereostructure of β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters synthesized by Bellassoued et al. [J. Org. Chem. 2001, 66, 5054–5057] using Mukaiyama aldol reaction has been reassigned using density functional theory NMR 1H chemical shifts calculations. It is now concluded that the major diastereoisomer is syn and the minor is anti. Within this assignment, for all silyl esters, δHa(anti) > δHa(syn), δHb(anti) < δHb(syn), and 3JHa-Hb (anti) > 3JHa-Hb (syn). Since the experimental assignment was based on the stereostructure (E/Z) of the cinnamic acid obtained by elimination of trimethylsilyl 3-phenyl-3-(trimethylsiloxy)-2-(trimethylsilyl)propanoate in the presence of TiCl4 and on the assumption that this elimination is anti stereospecific in acidic medium, one arrives at the conclusion that the elimination of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters is not anti stereospecific.",

keywords = "H NMR reassignment, Diastereoselectivity, Mukaiyama aldol reaction",

author = "{Hadj Mohamed}, Slim and Mahmoud Trabelsi and Beno{\^i}t Champagne",

note = "Funding Information: S.H.M. thanks the Fonds Sp{\'e}cial de Recherche of UNamur for his PhD grant. This work was supported by funds from the Belgian Government (IUAP No P7/5 “Functional Supramolecular Systems”) and the Francqui Foundation. The calculations were performed on the computers of the Consortium des {\'E}quipements de Calcul Intensif, including those of the Technological Platform of High-Performance Computing, for which we gratefully acknowledge the financial support of the FNRS-FRFC (Conventions No. 2.4.617.07.F and 2.5020.11) and of the University of Namur. Publisher Copyright: {\textcopyright} 2017 Elsevier B.V.",

year = "2017",

month = aug,

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doi = "10.1016/j.molstruc.2017.03.112",

language = "English",

volume = "1141",

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journal = "Journal of molecular structure",

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T1 - Assigning the stereochemistry of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters using GIAO 1H NMR chemical shift calculations

AU - Hadj Mohamed, Slim

AU - Trabelsi, Mahmoud

AU - Champagne, Benoît

N1 - Funding Information: S.H.M. thanks the Fonds Spécial de Recherche of UNamur for his PhD grant. This work was supported by funds from the Belgian Government (IUAP No P7/5 “Functional Supramolecular Systems”) and the Francqui Foundation. The calculations were performed on the computers of the Consortium des Équipements de Calcul Intensif, including those of the Technological Platform of High-Performance Computing, for which we gratefully acknowledge the financial support of the FNRS-FRFC (Conventions No. 2.4.617.07.F and 2.5020.11) and of the University of Namur. Publisher Copyright: © 2017 Elsevier B.V.

PY - 2017/8/5

Y1 - 2017/8/5

N2 - The stereostructure of β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters synthesized by Bellassoued et al. [J. Org. Chem. 2001, 66, 5054–5057] using Mukaiyama aldol reaction has been reassigned using density functional theory NMR 1H chemical shifts calculations. It is now concluded that the major diastereoisomer is syn and the minor is anti. Within this assignment, for all silyl esters, δHa(anti) > δHa(syn), δHb(anti) < δHb(syn), and 3JHa-Hb (anti) > 3JHa-Hb (syn). Since the experimental assignment was based on the stereostructure (E/Z) of the cinnamic acid obtained by elimination of trimethylsilyl 3-phenyl-3-(trimethylsiloxy)-2-(trimethylsilyl)propanoate in the presence of TiCl4 and on the assumption that this elimination is anti stereospecific in acidic medium, one arrives at the conclusion that the elimination of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters is not anti stereospecific.

AB - The stereostructure of β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters synthesized by Bellassoued et al. [J. Org. Chem. 2001, 66, 5054–5057] using Mukaiyama aldol reaction has been reassigned using density functional theory NMR 1H chemical shifts calculations. It is now concluded that the major diastereoisomer is syn and the minor is anti. Within this assignment, for all silyl esters, δHa(anti) > δHa(syn), δHb(anti) < δHb(syn), and 3JHa-Hb (anti) > 3JHa-Hb (syn). Since the experimental assignment was based on the stereostructure (E/Z) of the cinnamic acid obtained by elimination of trimethylsilyl 3-phenyl-3-(trimethylsiloxy)-2-(trimethylsilyl)propanoate in the presence of TiCl4 and on the assumption that this elimination is anti stereospecific in acidic medium, one arrives at the conclusion that the elimination of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters is not anti stereospecific.

KW - H NMR reassignment

KW - Diastereoselectivity

KW - Mukaiyama aldol reaction

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DO - 10.1016/j.molstruc.2017.03.112

M3 - Article

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SN - 0022-2860

VL - 1141

SP - 436

EP - 440

JO - Journal of molecular structure

JF - Journal of molecular structure

ER -

Assigning the stereochemistry of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters using GIAO ¹H NMR chemical shift calculations

Abstract

Keywords

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Projet de recherche de la thèse de Slim Hadj Mohamed

Functional Supramolecular Systems (IUAP No. P7/5) – Modeling the nonlinear optical properties of functionalized surfaced and complex systems

consortium des équipements de calcul intensif

High Performance Computing Technology Platform

Cite this

Assigning the stereochemistry of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters using GIAO 1H NMR chemical shift calculations

Abstract

Keywords

Access to Document

Other files and links

Fingerprint

Projects

Projet de recherche de la thèse de Slim Hadj Mohamed

Functional Supramolecular Systems (IUAP No. P7/5) – Modeling the nonlinear optical properties of functionalized surfaced and complex systems

consortium des équipements de calcul intensif

Equipment

High Performance Computing Technology Platform

Cite this

Assigning the stereochemistry of syn and anti β-trimethylsiloxy-α-trimethylsilyl alkanoic acid silyl esters using GIAO ¹H NMR chemical shift calculations