Intramolecular reactivity of a captodative bis-diene

[GRAPHICS] A 1,1-captodative bis-diene (3) has been prepared from crotonaldehyde diethyl acetal through an elimination-metalation sequence. This compound has been reacted with electron-rich and electron-deficient dienophiles. Under both thermal and high-pressure conditions, no intermolecular reaction was observed, the fused (4) and bridged (5) intramolecular bicyclic adducts being recovered. The reduction of the central carbonyl group has led to the corresponding allylic alcohol which, in thermal cycloaddition conditions, also provides an intramolecular adduct that aromatizes in the medium.