Novel Approach to Bridged Polynuclear Dihydroanthracene Systems via Regioselective Intramolecular Diels–Alder Reaction

A novel approach to the synthesis of bridged polynuclear dihydroanthracene heterocyclic systems via an anthracene-mediated intramolecular Diels-Alder reaction has been developed. Starting from commercially available 9-anthraldehyde, 9-anthrylmethylamines were synthesized using a one-pot procedure and subsequently employed in a tandem acylation-Diels-Alder cycloaddition reaction. Their reaction with maleic anhydride in refluxing benzene for 24 h afforded the corresponding products in yields of up to 90% as racemic mixtures, as confirmed by X-ray crystallographic analysis. The reaction with citraconic anhydride proceeded regioselectively at elevated temperature, providing the target product in a similar manner. In all cases, the reaction involved initial acylation of the amine followed by intramolecular cyclization onto the diene moiety, affording the corresponding products in 65-84% yields as racemic mixtures. A competition experiment demonstrated preferential cyclization involving the anthracene moiety over the furan ring. This methodology provides an efficient route to bridged polynuclear dihydroanthracene derivatives with potential applications in organic synthesis and materials science.