Keywords: Alkylation / Annulation / Carbocycles / Lithiation / Ozonolysis N-Alkylsuccinimides reacted with excess of LHMDS and 3-chloro-2-(chloromethyl)-1-propene to give in medium yields N-alkyl-3,7-dimethylenebicyclo[3.3.0]octane-1,5-dicarboximides, which were ozonized to the corresponding 3,7-dioxobicyclo[3.3.0]octane-1,5-dicarboximides. When these alkylations were carried out by using LDA as the base, cis-N-