The title 2-aza-1,3-diene reacted smoothly with C 6 0 at room temperature to give 2-piperidonefused C 6 0 after hydrolysis. A silyoxy group on the piperidone ring was replaced by alkoxy groups by acid-catalyzed substitution reaction with alcohols via an iminium cation intermediate. This type of reaction was applied to reduction by use of triethylsilane to give the parent δ-valerolactam derivative of C 6 0 .