Fused Dihydrodibenzobarrelene (Dibenzobicylco[2.2.2]octadiene) and Lactone Rings via Tandem Diels-Alder and Condensation Reactions of Dialkyl Fumarates and 9-Anthracenemethanol

A series of fused dihydrodibenzobarrelene (dibenzobicyclo[2.2.2]octadiene) and lactone rings were prepared from dialkyl fumarates and 9-anthracenemethanol. These products were prepared via a one-pot synthesis in which a Diels-Alder reaction occurred followed by an intramolecular transesterification to form the lactone ring. A key feature of this synthetic methodology is the straightforward purification of the reaction products, in most cases without the need for chromatography. The ease of work-up along with the simple setup of the reaction (no catalysts or other reagents needed) make this methodology a convenient and potentially scalable route to complex, multicyclic structures. Molecular modeling of the transition structures for Diels-Alder reaction suggested that transesterification could precede cycloaddition, but NMR in situ studies confirmed the opposite occurrence. Product formed exclusively in the trans configuration for all alkyl fumarates used.