A Simple Strategy for Spirocyclopentannulation of Cyclic Ketones. Formal Total Synthesis of (.+-.)-Acorone.

A general and simple methodology for spirocyclopentannulation of cyclic ketones (or 4,4-disubstituted cyclopentenones from acyclic ketones) and its application in the synthesis of the spirodienone 7 via a prochiral precursor constituting a formal total synthesis of (+/-)-acorone (6), are described.