title: A sulfinyl-directed asymmetric [5C + 2C] intramolecular acetoxypyranone-alkene cycloaddition.
abstract: [reaction: see text] Introduction of a homochiral p-tolylsulfinyl group at the trans terminal position of an alkene induces a total diastereodifferentiation in the intramolecular cycloaddition of the latter to 3-oxidopyrylium ylide precursors. The cycloadducts can be readily desulfinylated to afford enantiomerically pure oxa-bridged bicyclo[5.3.0]decane ring systems. Theoretical calculations confirm that diastereoselectivity stems from the conformational preferences of the alkenylsulfoxide unit in the transition state of the reaction.
authors.affiliation: Departamento de Química Orgánica y Unidad Asociada al CSIC, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: López
authors.forename: Luis
authors.initials: L
authors.lastname: Castedo
authors.forename: José L
authors.initials: JL
authors.lastname: Mascareñas