Radical Cyclisation of -Halo Aluminium Acetals: A Mechanistic Study

-Bromo aluminium acetals are suitable substrates for Ueno-Stork-like radical cyclisations affording -lactols and acid-sensitive methylene--lactols in high yields. The mechanistic study herein sets the scope and limitation of this reaction. The influence of the halide (or chalcogenide) atom X (X=Cl,...

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Published inChemistry : a European journal Vol. 22; no. 14; pp. 4809 - 4824
Main Authors Beneteau, Romain, Boussonniere, Anne, Rouaud, Jean-Christophe, Lebreton, Jacques, Graton, Jerome, Jacquemin, Denis, Sebban, Muriel, Oulyadi, Hassan, Hamdoun, Ghanem, Hancock, Amber N., Schiesser, Carl H., Denes, Fabrice
Format Journal Article
LanguageEnglish
Published WEINHEIM Wiley 24.03.2016
Wiley Subscription Services, Inc
Subjects
Acetals
Alcohols
Aluminum
Analogies
Aquatic birds
Chemistry
Chemistry, Multidisciplinary
Diffusion
Intermediates
Magnetic resonance spectroscopy
Mathematical analysis
Methylene
NMR spectroscopy
Oxygen
Physical Sciences
Science & Technology
Substrates
Temperature effects
computational methods
HOMOLYTIC SUBSTITUTION-REACTIONS
ALKOXIDES
MOLECULAR-STRUCTURE
AB-INITIO
reaction mechanisms
PHASE ELECTRON-DIFFRACTION
UENO-STORK REACTION
radical cyclisation
SYNTHETIC ROUTE
GAMMA-BUTYROLACTONES
PRODUCTS
aluminium acetals
NMR spectroscopy
NMR-SPECTROSCOPY DOSY
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Summary:-Bromo aluminium acetals are suitable substrates for Ueno-Stork-like radical cyclisations affording -lactols and acid-sensitive methylene--lactols in high yields. The mechanistic study herein sets the scope and limitation of this reaction. The influence of the halide (or chalcogenide) atom X (X=Cl, Br, I, SPh, SePh) in the precursors -haloesters, as well as influence of the solvent and temperature was studied. The structure of the aluminium acetal intermediates resulting from the reduction of the corresponding -haloesters has been investigated by low-temperature C-13-INEPT diffusion-ordered NMR spectroscopy (DOSY) experiments and quantum calculations, providing new insights into the structures of these thermally labile intermediates. Oxygen-bridged dimeric structures with a planar Al2O2 ring are proposed for the least hindered aluminium acetals, while monomeric structures seem to prevail for the most hindered species. A comparison against the radical cyclisation of aluminium acetals derived from allyl and propargyl alcohols with the parent Ueno-Stork has been made at the BHandHLYP/6-311++G(d,p) level of theory, highlighting mechanistic similarities and differences.
Bibliography:Agence Nationale de la Recherche (ANR)
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201504780