Imidazolfarbstoffe IV. Kondensation von o-Phenylendiamin mit Phthalanhydrid

11H-isoindolo[2,1-a]benzimidazoles (Review)

“…Arient's conclusion that compound 31 is formed as a result of the hydrolysis of the isoindolobenzimidazolone 4a [28,30] does not agree with the data in [29,32]. Either fusion of compounds (29) or (30) at 250-290°C or boiling in acetic anhydride is recommended for the synthesis of 4a [28].…”

“…Various products can be formed in this reaction (see the scheme below), depending on the conditions [28,29]. At moderate temperature in methanol small amounts of the polyamide of phthalic acid 29 and substituted phthalimide 30 are formed [30]. With boiling only a mixture (1:1) of compound 30 and benzimidazolyl-substituted benzoic acid 31 is obtained.…”

“…The composition of the mixture does not change with further heating [28]. In water and acetic acid when the boiling point of the reaction mass is reached the initially formed phthalimide 30 is mainly transformed into the substituted benzoic acid 31 and also (in small amounts) into the required isoindolobenzimidazolone 4a and bis(2-benzimidazolyl)benzene 32 [28,30]. Products with the same composition are obtained in pyridine, while in nitrobenzene the reaction is accelerated and the content of compound 4a is increased [28].…”

IR.‐spektroskopische Untersuchungen in der Imidazol‐Reihe

“…Wir wollten hauptsachlich prufen, ob anhand der 1R.-Spektren einfach und schnell die Grosse des ankondensierten Ringsystems bestimmt und ob ferner die Kondensation von cyclischen Anhydriden mit 0-bzw. #eri-standigen Diaminen verfolgt werden konnte.((Benzoylen-benzimidazolo (I) [9] [lo], ((Phtaloperinon-10)) (11) [ll] [12], ctl,8-NaphtoyIen-benzimidazoln (111) [13] [14], ((Naphtaloperinon), (IV) [15] und das un-…”

“…((Benzoylen-benzimidazolo (I) [9] [lo], ((Phtaloperinon-10)) (11) [ll] [12], ctl,8-NaphtoyIen-benzimidazoln (111) [13] [14], ((Naphtaloperinon), (IV) [15] und das un-…”