). As models for the ionization of orthoesters, a series of 1,3-dioxan-2-ylium salts have been prepared and characterized. The properties of 1,3-dioxan-2-ylium hexachloroantimonate 1, 5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate 2, 2-methyl-5-ethoxymethy 1-1,3-dioxan-2-ylium hexachloroantimonate 3, and 2-phenyl-5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate 4, have been studied by 'H and I3C NMR spectroscopy. The structures of 3 and 4 have been determined using X-ray crystallography. Salts 3 and 4 both crystallize in monoclinic crystal systems. For 3, the space group is C2/c, with a est dispose au-dessus du cycle dioxan-2-ylium. Toutefois, l'interaction entre l'oxygbne de 1'Cther et le centre cationique n'est pas important du B la grande distance internuclkaire qui est observCe. On a prepare le cation 5 dans lequel la longueur de la chaine carbonCe entre l'oxygbne de 1'Cther et le C(5) est augmentCe. On a trouvC que cet ion subit un rearrangement intramoleculaire rCversible conduisant B la formation de 1'hexachloroantimonate du 1-mCthyl-4-acCtoxymCthyl-tCtrahydrofurany1 oxonium.[Traduit par la rkdaction]

No abstract