A new tricyclic π-conjugated system, cyclopent [a] azulen-3 (H)-one, was prepared by flash vacuum pyrolysis on the final step. All proton signals of this molecule were observed at higher magnetic resonance field than expected in terms of induced paramagnetic ring current in the periphery of this molecule.
![cyclopenta[a]azulen-3-one Structure](https://image.chemsrc.com/caspic/205/140666-49-5.png)