Formation of a new polycyclic heteroring system by the acid-catalyzed rearrangement of thebaine in the presence of thiosalicylic acid

The methanesulfonic acid-catalyzed rearrangement of thebaine (1) in the presence of thiophenol resulted in 2-phenylthioapocodeine (7), whose O-demethylation gave 2-phenylthioapomorphine (8). An analogous transformation of1 with thiosalicylic acid furnished the ethers (6) and (11) together with a polycyclic ketone (12) and a polycyclic acetal (15). Upon treatment of the acetal (15) with acid the thioxanthylium salt (16) was prepared.