Construction of a fully substituted cyclopentenone as the core skeleton of stemonamide via a Nazarov cyclization

A synthetic study of the Stemona alkaloid stemonamide is described. The FeCl3-promoted fast Nazarov reaction of β-alkoxy divinyl ketones in the presence of t-BuOH afforded an α-methylene cyclopentenone, which was subsequently subjected to the Rh-catalyzed C–H amination to provide a fully appropriately substituted α-methylene cyclopentenone as the core skeleton of stemonamide.