Synthesis of polycyclic naphthols and naphthalenes: Via tandem Ti(O i-Pr)₄-promoted photoenolization Diels-Alder reaction and aromatization

An efficient approach to naphthol and naphthalene scaffolds has been developed using a sequence involving tandem Ti(Oi-Pr)4-promoted photoenolization Diels-Alder (PEDA) and aromatization reactions. Starting with photoenolizable ortho-tolualdehyde derived dienes, the sequence using sterically hindered cyclohexenone and cyclopentenone dienophiles construct naphthol- A nd naphthalene-fused polycyclic products, respectively. The strategy was successfully utilized to synthesize the core skeletons of the bioactive marine natural products garveatin C and exiguaquinol.