Ylures de carbonyle dérivés de gem-dicyanoépoxydes : Stéréochimie des dioxolannes obtenus par addition d'aldéhydes aux ylures de carbonyle

The reaction of aldehydes with 1,1-dicyano oxirans gives dioxolanes. The structure of these adducts, established by NMR and through boron trifluoride equilibration, is proof of the CC ring scission of the oxirans. The effect of substituants on the reactivity of aldehydes with carbonyl ylides is discussed. The occurrence of a non concerted reaction is considered in an extreme case.