Opening of a 1,3-dioxolane by nucleophilic attack at a ketal methylene

A novel type of opening of an ethylene ketal has been observed in the reaction of 1 with alane RA1Me₂. The reaction is explained in terms of a nucleophilic attack on the ketal methylene synchronous with participation by one of the ketal oxygens in the opening of the epoxide function located across the 7-membered ring of 1.