Premium
The reaction of 1‐hydrazinophthalazine with phthalaldehydic acid. Occurrence of ring‐chain tautomers
Author(s) -
Amer Adel,
Zimmer Hans
Publication year - 1981
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570180828
Subject(s) - phthalazine , tautomer , chemistry , ring (chemistry) , solvent , medicinal chemistry , ethanol , stereochemistry , organic chemistry
Abstract A reaction involving 1‐hydrazinophthalazine (hydralazine, 1)designed to give a condensed heterocyclic system in which an eight membered ring is fused to phthalazine was investigated. With phthalaldehydic acid (2) the expected system was obtained. However, it occurs as an easily convertible mixture of ring‐chain tautomers. It was found that the course of the reaction depends on the solvent. Thus, 6,7‐dihydro‐7‐hydroxy‐12 H ‐phthalazino[2,1‐ b ][2,4]benzodiazocin‐12‐one ( 5 ) and 2‐(2‐formylbenzoyl)‐1‐hydrazono‐1,2‐dihydrophthalazine ( 6 ) were the products of the reaction of 1 with 2 in aqueous medium. Upon prolonged standing this mixture converts into 3‐(2‐carboxyphenyl)‐ s ‐triazolo[3,4‐ a ]phthalazine ( 8 ). In contrast, the isomeric ring‐chain tautomers 2‐(1‐aminophthalazino)‐3‐hydroxy‐1‐oxoisoindole ( 12 ) and 1‐[2‐(2‐formylbenzoyl)hydrazino]phthalazine ( 13 ) were formed when the reaction was run in ethanol as solvent.