title: Electrochemically-induced spirolactonization of alpha-(methoxyphenoxy)alkanoic acids into quinone ketals.
abstract: Anodic oxidation of two series of alpha-(2)- and alpha-(4-methoxyphenoxy)alkanoic acids were studied both at the analytical and preparative scales in order to delineate mechanistic aspects of electrochemically induced spirolactonization and to develop synthetically useful orthoquinone bis- and monoketals. Although alpha-monomethylated carboxylic acids and acetic acid derivatives do not undergo any spiroannulation, alpha-dimethylated carboxylic acids furnished spirolactones in high yields. A gem-dimethyl effect is invoked to explain these differences in cyclization capacity. Electrooxidation conditions can be selected to furnish either quinone spirolactone bis- or monoketals. Chemoselective monohydrolysis of bisketals can also be accomplished in a stepwise fashion to furnish the corresponding spirolactone monoketals, but the ortho compound unfortunately dimerized in situ via a Diels-Alder process. An ECEC pathway is proposed to rationalize the observed spirolactonizations on the basis of cyclic voltammetry analyses.
authors.affiliation: Laboratoire de Chimie des Substances Végétales, Centre de Recherche en Chimie Moléculaire, Université Bordeaux 1, 351 cours de la Libération, 33405 Talence Cedex, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Deffieux
authors.forename: Isabelle
authors.initials: I
authors.lastname: Fabre
authors.forename: Christian
authors.initials: C
authors.lastname: Courseille
authors.forename: Stéphane
authors.initials: S
authors.lastname: Quideau