Reaction of pyridinium phenacylides with cyclopentadienone derivatives gave bicyclo [3.1. 0] hex-3-en-2-one derivatives by the nucleophilic addition reaction followed by pyridine elimination. Isoquinolinium phenacylide underwent the 1, 3-dipolar cycloaddition reaction with a cyclopentadienone.
![Bicyclo[3.1.0]hex-3-en-2-one,6-benzoyl-4,5-di-2-furanyl-1,3-dimethyl-, (1a,5a,6b)- (9CI) Structure](https://image.chemsrc.com/caspic/356/86551-99-7.png)