Electrochemical synthesis of dimerizing and nondimerizing orthoquinone monoketals.
Anodic oxidation of appropriately substituted 2-methoxyphenols or alpha-(2-methoxyphenoxy)-2-methylpropionic acids in the presence of methanol furnishes stable orthoquinone monoketals, and thus constitutes a valuable alternative to the use of chemical oxidants that are often based on toxic metallic species. The propionic acid derivatives are initially converted into O-spirolactonic quinone bisketals that are then selectively hydrolyzed into the desired monoketal compounds. In the absence of blocking substituents, orthoquinone monoketals spontaneously undergo Diels-Alder dimerizations into tricyclododecadienedienones with extraordinary site selectivity, regioselectivity, and stereoselectivity. Suggestions are made to open up a new track for a long awaited rationalization of these controls on the basis of the intramolecular [2 + 2] reactivity of these orthoquinone monoketal-derived cyclodimers.
Deffieux
Denis
D
Laboratoire de Chimie des Substances Végétales, Centre de Recherche en Chimie Moléculaire, Université Bordeaux 1, 351 cours de la Libération, F-33405 Talence Cedex, France.
Fabre
Isabelle
I
Titz
Alexander
A
Léger
Jean-Michel
JM
Quideau
Stéphane
S
D019281:Dimerization; D004563:Electrochemistry; D007659:Ketones / Q000138:chemical synthesis*; D010084:Oxidation-Reduction; D011809:Quinones / Q000138:chemical synthesis*; D013237:Stereoisomerism
D007659:Ketones; D011809:Quinones