Pyrolysis and Photolysis of the N-Oxides of Protopines and Hexahydrobenzo [c] phenanthridines. Syntheses of the Secoberbines and Benzo [c] phenanthridines

Abstract

Pyrolysis and photolysis of the N-oxides of the protopines 9 and 16 produces the ring-enlarged compounds 10 and 17, whose reduction with zinc in acetic acid leads to the secoberbines (±)-corydalisol (11) and (±)-hypecorine (12) from 9, and the corresponding analogs (18 and 19) from 16. Pyrolysis of (+)-chelidonine N-oxide (24) generates dihydrosanguinarine (22).