ETUDE DES PETITS CYCLES-XLIV. UNE VOIE DE SYNTHESE DES ACYL-2 CYCLOBUTANONES

Article abstract of DOI:10.1016/S0040-4020(01)91582-0

Organic peracid oxidation of α-cyclopropylidene ketones and acetals substituted in the vinylic position leads to the corresponding oxaspiropentyl ketones and acetals.Esters are also formed from the products of the Baeyer-Villiger oxidation; they are easily removed from the crude product.Unsubstituted oxaspiropentyl ketones are not obtained by this method; they are obtained by oxidation of oxaspiropentyl alcohols ( formed by epoxidation of α-cyclopropylidene alcohols).The isomerisation, either spontaneous or through reaction with lithium halides, of oxaspiropentyl ketones and acetals, gives 2-acyl-cyclobutanones and corresponding mono-acetals.These new unstable 1,3-diones must be stored in CCl4 solution.They are present in the dione form only.They add water and methanol, in acidic and even in neutral medium, leading to ring opening products. 2-Benzoyl cyclobutanone 4g is easily rearranged into 3,4-dihydro-6-phenyl 2-pyrone 12.Deacetalization of the 2-acyl-cyclobutanones mono-acetals 7B-11b into the corresponding diones is not possible even by the moist silicagel technique.