Intramolecular diels-alder reaction with furan-diene. A novel potential entry to steroids.

Depending on the reaction conditions the intramolecular Diels-Alder reaction of furan-diene $\text{14}$ yields predominantly either one of two adducts $\text{16a}$ and $\text{16b}$, which possess the necessary functionality for eventual transformation into corticosteroids. The dienophile was introduced via alkylation of the enolate, formally obtained upon lithium-liq. ammonia reduction of 3-furyl-2-methyl-2-cyclopentenone ($\text{7}$).