- Radical Cyclisation of α-Halo Aluminium Acetals: A Mechanistic Study
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α-Bromo aluminium acetals are suitable substrates for Ueno-Stork-like radical cyclisations affording γ-lactols and acid-sensitive methylene-γ-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 α-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 α-haloesters has been investigated by low-temperature 13C-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.
- Bénéteau, Romain,Boussonnière, Anne,Rouaud, Jean-Christophe,Lebreton, Jacques,Graton, Jéro?me,Jacquemin, Denis,Sebban, Muriel,Oulyadi, Hassan,Hamdoun, Ghanem,Hancock, Amber N.,Schiesser, Carl H.,Dénès, Fabrice
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supporting information
p. 4809 - 4824
(2016/04/05)
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- Radical cyclization of α-bromo aluminum acetals onto alkenes and alkynes (radic[al] process): A simple access to γ-lactols and 4-methylene-γ-lactols
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An efficient preparation of γ-lactols and methylene-γ-lactols is described. Highly acid-sensitive lactols are prepared in a concise manner by using a radical cyclization of aluminum acetals. The precursors for the radical reactions are readily prepared fr
- Boussonniere, Anne,Beneteau, Romain,Zimmermann, Nicolas,Lebreton, Jacques,Denes, Fabrice
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supporting information; experimental part
p. 5613 - 5627
(2011/06/22)
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- Radical cyclization of α-bromo aluminum acetals: An easy approach to γ-lactols
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[Chemical equation presented] Running rings around aluminum: An efficient procedure for radical cyclization α-bromo esters is reported. Reduction of the esters by DIBAL-H at low temperature gives aluminum acetals, which are cyclized in the presence of nBu
- Boussonniere, Anne,Denes, Fabrice,Lebreton, Jacques
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supporting information; experimental part
p. 9549 - 9552
(2010/03/25)
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