Electrooxidative Cyclization of 1-Benzyltetrahydroisoquinolines. A Novel Nonphenol Coupling Reaction

(±)-Laudanosine was oxidized at platinum in a three-compartment cell at 1.1 V in acetonitrile at 0° in the presence of Na₂CO₃. Either lithium perchlorate or tetramethylammonium tetrafluoroborate was the background electrolyte. O-Methylflavinantine was isolated from the anolyte in 52 % yield. Similar oxidation of (±)-O-benzylcodamine, (±)-O-benzylpseudocodamine, (±)-O-benzyllaudanine, and (±)-O-benzylpseudolaudanine yielded O-methylflavinantine, O-benzylflavinantine, O-benzylisoflavinantine, and 2,3-dimethoxy-6-benzyloxymorphinandienone, respectively. Oxidation of (±)-laudanosine in the presence of equal molar bis(acetonitrile)- palladium(II) chloride enhanced the O-methylflavinantine yield to 63 %.