Abstract The addition of maleic anhydride to phthalazine is confirmed to form a five- membered pyrrolidino ring fusion to phthalazine VI, rather than a pyridophthalazine II, by means of synthetic and degradative experiments, and proton and carbon-13 nmr. Two of probable three isomers obtained have been isolated and the stereochemistry partially established. Comparison of the data obtained for this adduct with the data obtained for the ...
![spiro[9a,9b-dihydro-3aH-furo[1,2]pyrrolo[3,5-b]pyridazine-4,3'-oxolane]-1,2',3,5'-tetrone Structure](https://image.chemsrc.com/caspic/160/65251-27-6.png)