Abstract A novel and very short synthesis of the useful title hydrocarbon 2 is presented. Its key step is based on a Diels-Alder reaction of isobenzofuran 4. The lithium salt of 2 gives a remarkably stable valence isomer of anthracene 1 in a reaction analogous to the indene→ benzobenzvalene transformation.
![(1H-cyclopenta[b]naphthalen-1-yl)lithium Structure](https://image.chemsrc.com/caspic/336/129815-98-1.png)
