A simple heterocyclic fusion reaction and its application for expeditious syntheses of rutaecarpine and its analogs

In the search for new inhibitors of cholinesterases, a simple heterocyclic fusion reaction of isatoic anhydride 8 and 3,4-dihydroisoquinoline 22 was discovered which involves a spontaneous dehydrogenation upon heating. Applying the reaction, the bioactive natural alkaloid rutaecarpine and several substituted derivatives out of tryptamines and anthranilic acids or isatoic anhydrides, respectively, can be synthesized without tedious chromatographic purification. This provides simple and fast access to larger amounts of compounds with this privileged structure in medicinal chemistry.