Synthesis of new condensed nitrogen heterocyclic systems

A cotarnine alkaloid-based synthesis was developed for new heptacyclic condensed diisoquinolines via the double intramolecular pseudosalt bis1,3]dioxolo4,5-g;4′,5′-g′]1,3,4]oxadiazolo2,3-a;5,4-a′]diisoquinoline 6. Substitution of the central O atom in 6 by C, S, or N nucleophiles afforded the first representatives of the new ring systems bis1,3]dioxolo4,5-g:4,5-g′]pyrazolo3,2-a:5,1-a′]diisoquinoline (7a-d), bis1,3]dioxolo4,5-g:4,5-g′]1,3,4]thiadiazolo2,3-a:5,4-a′]diisoquinoline (8), and bis1,3]dioxolo4,5-g:4,5-g′]1,2,4]triazolo3,2-a:5,1-a′]diisoquinoline (9a-d) under simple reaction conditions.