Synthesis and Transformations of Metallacycles. Part 34. New Method for the Synthesis of Spiro[3.3]heptanes and Spiro[3.4]octanes by Cycloalumination of Methylidenecyclobutanes with Et3Al in the Presence of a Cp2ZrCl2 Catalyst.

Zirconocene-catalyzed reaction of polycyclic methylenecyclobutane derivatives, e.g. (I), with Et3Al generates 5-membered cycloaluminates like (III) which can be quenched by reaction with sulfur, selenium, allyl chloride or methyl formate to give spirocyclic derivatives, e.g. (IV), (VI), (VII).