Journal of Organic Chemistry vol:56 issue:7 pages:2386-2390
Mercuric acetate oxidation of 1-benzyl-3,3-(ethylenedioxy)piperidine (1) and of 3-CO2Et- and 3-CH2OH-substituted piperidines 7-9 was shown to occur regioselectively at the 6-position. Trapping of the resulting 6-iminium ions with cyanide yielded the corresponding 5-substituted 2-piperidinecarbonitriles 5, 10, and 11. However, the 2-iminium ion was formed in the reaction of the N-oxide of 1 with trifluoroacetic anydride; with cyanide this afforded the regioisomeric 3,3-(ethylenedioxy)-2-piperidinecarbonitrile (2). Plausible mechanisms are advanved to explain this contrasting behavior. 1-Benzyl-5,5-(ethylenedioxy)-2-piperidinecarbonitrile (5) was transformed into other piperidine-2,5 derivatives by reaction of the alpha-amino nitrile anion with electrophoresis, followed by reductive decyanation.