Reaction of quinidine acetate, epiquinidine and its acetate in superacid: formation of gem-difluoro derivatives with or without rearrangement

In HF–SbF5, quinidine or its dihydrochloride cyclises previously obtained with usual acids. A similar reaction is observed in the presence of CCl4. Under similar conditions quinidine acetate and epiquinidine acetate dihydrochlorides both yield 10,10-difluoro derivatives epimeric at C-3, and , and and , and a rearranged difluoro derivative and , respectively. Epiquinidine leads to the expected analogues and and to a ketone . Formation of gem-difluoro compounds implies chloro intermediates at C-10, precursors of α-chlorocarbenium ions, which are trapped by a fluoride ion and which lead by halogen exchange to the products.