Reactions of Lucigenin in protic solvents in the presence of amines

Lucigenin (N,N′-dimethyl-9,9′-biacridinium nitrate) 1 on heating under reflux in protic solvents in the presence of amines gives rise to the N,N′-dimethyl-9,9′-biacridylidene 2 (DBA) or protected hemiaminal N-methoxymethyl-9,9′-bi-acridylidene 3 . On the other hand acid hydrolysis and synchronous oxidation of hemiaminal 3 followed by reaction of monomethyl-biacridinium nitrate 4 with sodium hydroxide in methanol or water leads to biacridine 5 (overall yield ca. 33%).