Synthesis of 6-Amino-3,4-dihydroisoquinolinium Derivatives by Ring-Opening Reactions of Acridizinium Ions

The reaction of the 9-fluoroacridizinium (9-fluorobenzo[<i>b</i>]quinolizinium) or the 9-aminoacridizinium (9-aminobenzo[<i>b</i>]quinolizinium) ion with primary alkyl amines gives with high diastereoselectivity 6-amino-3,4-dihydroisoquinolinium derivatives as main products, which exhibit pronounced absorption and fluorescence properties. It is proposed that the reaction proceeds via a nucleophilic ring-opening followed by an aza Diels−Alder reaction.