title: Radical Cyclisation of α-Halo Aluminium Acetals: A Mechanistic Study.
abstract: 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 (13) C-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 Al2 O2 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.
authors.affiliation: CEISAM UMR 6230 - UFR des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière BP, 92208-44322, Nantes Cedex 3, France.
authors.forename: Romain
authors.identifier: http://orcid.org/0000-0002-6171-7430
authors.initials: R
authors.lastname: Bénéteau
authors.affiliation: CEISAM UMR 6230 - UFR des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière BP, 92208-44322, Nantes Cedex 3, France.
authors.forename: Anne
authors.identifier: http://orcid.org/0000-0002-1113-099X
authors.initials: A
authors.lastname: Boussonnière
authors.affiliation: CEISAM UMR 6230 - UFR des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière BP, 92208-44322, Nantes Cedex 3, France.
authors.forename: Jean-Christophe
authors.identifier: http://orcid.org/0000-0002-4238-874X
authors.initials: JC
authors.lastname: Rouaud
authors.affiliation: CEISAM UMR 6230 - UFR des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière BP, 92208-44322, Nantes Cedex 3, France.
authors.forename: Jacques
authors.identifier: http://orcid.org/0000-0003-2603-8982
authors.initials: J
authors.lastname: Lebreton
authors.affiliation: CEISAM UMR 6230 - UFR des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière BP, 92208-44322, Nantes Cedex 3, France.
authors.forename: Jérôme
authors.identifier: http://orcid.org/0000-0002-1114-200X
authors.initials: J
authors.lastname: Graton
authors.affiliation: CEISAM UMR 6230 - UFR des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière BP, 92208-44322, Nantes Cedex 3, France.|Institut Universitaire de France, 1, rue Descartes, 75231, Paris Cedex 05, France.
authors.forename: Denis
authors.identifier: http://orcid.org/0000-0002-4217-0708
authors.initials: D
authors.lastname: Jacquemin
authors.affiliation: Normandie Université, COBRA UMR6014, FR3038, Université de Rouen; INSA de Rouen; CNRS, 76821, Mont-Saint-Aignan Cedex, France.
authors.forename: Muriel
authors.identifier: http://orcid.org/0000-0002-7907-1092
authors.initials: M
authors.lastname: Sebban
authors.affiliation: Normandie Université, COBRA UMR6014, FR3038, Université de Rouen; INSA de Rouen; CNRS, 76821, Mont-Saint-Aignan Cedex, France.
authors.forename: Hassan
authors.identifier: http://orcid.org/0000-0001-5813-1482
authors.initials: H
authors.lastname: Oulyadi
authors.affiliation: Normandie Université, COBRA UMR6014, FR3038, Université de Rouen; INSA de Rouen; CNRS, 76821, Mont-Saint-Aignan Cedex, France.
authors.forename: Ghanem
authors.identifier: http://orcid.org/0000-0002-1103-8499
authors.initials: G
authors.lastname: Hamdoun
authors.affiliation: School of Chemistry and, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Amber N
authors.identifier: http://orcid.org/0000-0002-5269-7300
authors.initials: AN
authors.lastname: Hancock
authors.affiliation: School of Chemistry and, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Carl H
authors.initials: CH
authors.lastname: Schiesser
authors.affiliation: CEISAM UMR 6230 - UFR des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière BP, 92208-44322, Nantes Cedex 3, France. fabrice.denes@univ-nantes.fr.
authors.forename: Fabrice
authors.identifier: http://orcid.org/0000-0002-9791-3177
authors.initials: F
authors.lastname: Dénès
keywords: NMR spectroscopy; aluminium acetals; computational methods; radical cyclisation; reaction mechanisms