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. This work represents the discovery of a new synthesis method to produce complex structures, fused dihydrodibenzobarrelene (dibenzobicylco[2.2.2]octadiene) lactone rings, via a simple one‐pot synthesis. Pure compounds were obtained from simple precipitation without need for further purification. Quantum calculations, in addition to experimental investigation, provided insight and characterization into the mechanism of this reaction. The ability to apply this reaction to a range of fumarates was explored, opening a wide range of possible new structures that can synthesized using this method.