Syntheses and properties of benzodipyrrinones

摘要

2,3-Benzannelated dipyrrinone analogs (1 and 2) of xanthobilirubic acid (3) are prepared by base-catalyzed condensation of isoindolinone (5) and indolin-2-one (6) respectively, with methyl 3-(2-formyl-3,5-dimethyl-1H-pyrrol-4-yl)propanoate (4). Nuclear Overhauser effect H-nmr studies indicate that both 1 and 2 adopt preferentially a syn-Z configuration. The former forms a hydrogen-bonded homodimer in nonpolar solvents; the latter is intramolecularly hydrogen bonded. [References: 15]